New files and better disasm

hw/monroe_oc8820_r3.00.asm

@@ -1,25 +1,118 @@
-; z80dasm 1.1.6
-; command line: z80dasm -g 0000h -l -a -b block_monroe_oc8820_r3.00 -o monroe_test.asm ../prom/monroe_oc8820_boot_prom_r3_00C_tms2516_ea751e22.bin
-displaymem equ 0x3000
-nomemchecks equ 9
+; ================================================================================
+; Monroe OC8820 Boot ROM Disassembly - Version R3.00C
+; ================================================================================
+; Original file: monroe_oc8820_boot_prom_r3_00C_tms2516_ea751e22.bin
+; ROM Type: TMS2516 (2KB EPROM)
+; Disassembler: z80dasm 1.1.6
+; 
+; This is the boot ROM for the Monroe OC8820 computer system.
+; The system uses a Z80 CPU with bank-switched memory architecture.
+;
+; Memory Map:
+; 0x0000-0x07FF : Boot ROM (this code)
+; 0x3000-0x3FFF : Display memory
+; 0xC000-0xFFFF : Banked RAM (controlled by I/O ports)
+; 0xFF80-0xFFFF : System variables area
+;
+; I/O Port Map:
+; 0x78-0x7B     : Hard disk controller (DMA-based)
+; 0xA0          : DART A (Dual Async Receiver/Transmitter) - Channel A data (printer)
+; 0xA1          : DART A (Dual Async Receiver/Transmitter) - Channel A command
+; 0xA2          : DART B (Dual Async Receiver/Transmitter) - Channel B data (keyboard)
+; 0xA3          : DART B (Dual Async Receiver/Transmitter) - Channel B command  
+; 0xA4          : SIO A (Serial I/O) - Channel A data (comm)
+; 0xA5          : SIO A (Serial I/O) - Channel A command
+; 0xA6          : SIO B (Serial I/O) - Channel B data (RS-232C)
+; 0xA7          : SIO B (Serial I/O) - Channel B command
+; 0xA8          : CTC (Counter Timer Circuit) - Channel 0 (Communications baud)
+; 0xA9          : CTC Channel 1 (AUX RS-232C baud)
+; 0xAA          : CTC Channel 2 (Printer baud)
+; 0xAB          : CTC Channel 3
+; 0xB0-0xB3     : Floppy disk controller (WD179x family)
+;                  0xB0: Status/Command, 0xB2: Sector, 0xB3: Track
+; 0xB4-0xB5     : Z80 PIO A data and control ports
+;                  0xB4: PIO A data (floppy INTRQ signal, DMA control), 0xB5: PIO A control
+; 0xB8-0xB9     : CRT controller (6845 CRTC)
+;                  0xB8: Register select, 0xB9: Data
+; 0xC0          : Floppy drive selection and control
+; 0xC4          : Program map A base address (memory banking)
+; 0xC5          : Program map B base address (memory banking)
+; 0xC6          : DMA map A base address (floppy DMA control)
+; 0xC7          : DMA map B base address (hard disk DMA control)
+; 0xC8          : Map and system control register (banking enable/disable)
+; 0xD4-0xD8     : Graphics and color control
+; 0xFF          : Hardware detection port
+;
+; Boot Device Selection System:
+; The Monroe OC8820 features sophisticated multi-device boot capability:
+;
+; 1. HARDWARE AUTO-DETECTION (Port 0xFF):
+;    - Reading 0 = Floppy-only configuration
+;    - Reading 1 = Hard disk + floppy configuration  
+;    - Reading 2+ = Advanced hard disk configuration
+;
+; 2. BOOT PRIORITY ORDER:
+;    - HARD DISK FIRST (when detected): Uses DMA controller at ports 0x78-0x7B
+;    - FLOPPY FALLBACK: Uses WD179x controller at ports 0xB0-0xB3 (PIO A at 0xB4-0xB5)
+;    - Systematic retry: Tests floppy drives 0-3 with 8 total attempts
+;    - Final recovery: Special commands 0x10/0x11 on Drive 0 only
+;
+; 3. DUAL OPERATING SYSTEM SUPPORT:
+;    - Monroe OS8 (proprietary system)
+;    - CP/M (industry standard) 
+;    - Boot path selection via calculated jumps at 0x05D0
+;
+; Communication Specifications:
+; DART A & B    : High-speed serial (baud rate depends on system clock)
+; SIO A & B     : High-speed serial (same rate as DART ports)
+; Printer Port  : Lower-speed serial/parallel (baud rate depends on system clock)
+; CTC Timing    : Ch0/1: ÷16 prescaler, time const 3; Ch2: ÷256 prescaler, time const 78
+        ; Number of memory banks to test
+; CRT Display   : 80 characters/line text mode (184 total horizontal timing)
+; ================================================================================
+; Constants
+displaymem: equ 0x3000		; Start of display memory
+nomemchecks: equ 9		; Number of memory banks to test (1-9)
+
 	org	00000h
 
+; ================================================================================
+; RESET VECTOR AND BOOT SEQUENCE
+; ================================================================================
+; Z80 starts execution here after reset
+
 l0000h:
-	di			;0000  no interrupt
-	ld sp,0ffa6h		;0001  init stack
-	xor a			;0004  A=0
-	jp l_init		;0005 go init 00046h
-	ld de,0303eh		;0008 point to screen ram
-	call cleartopline		;000b go clear top line 0052dh	
-	nop			;000e
-	nop			;000f
-	pop hl			;0010 get return addr
+	di			;0000  Disable interrupts during boot
+	ld sp,0ffa6h		;0001  Initialize stack pointer (top of RAM minus workspace)
+	xor a			;0004  Clear A register (A=0)
+	jp l_init		;0005  Jump to main initialization routine
+
+; ================================================================================
+; DISPLAY MESSAGE ROUTINE ENTRY POINT
+; ================================================================================
+; This routine is called to display text messages on screen
+; Entry: DE = screen position, HL = message address
+; Message format: first byte = length, followed by ASCII text
+
+display_entry:
+	ld de,0303eh		;0008  Default screen position (row 3, col 62?)
+	call cleartopline	;000b  Clear the top line of display
+	nop			;000e  Padding
+	nop			;000f  Padding
+	pop hl			;0010  Get return address (points to message)
+
 displaymsg:
-	ld c,(hl)			;0011 load count
-	inc hl			;0012 bump
-	ld b,000h		;0013
-	jp printroutine		;0015
-	rst 38h			;0018
+	ld c,(hl)		;0011  Load message length from first byte
+	inc hl			;0012  Point to message text
+	ld b,000h		;0013  Clear B (BC now = message length)
+	jp printroutine		;0015  Jump to print routine
+; ================================================================================
+; RST VECTOR TABLE (0x0018-0x003F)
+; ================================================================================
+; All RST vectors point to RST 38h (0x0038) - likely a common error handler
+; The Z80 RST instructions provide fast calls to these addresses
+
+	rst 38h			;0018  RST 18h -> RST 38h
 	rst 38h			;0019
 	rst 38h			;001a
 	rst 38h			;001b
@@ -27,7 +120,7 @@ displaymsg:
 	rst 38h			;001d
 	rst 38h			;001e
 	rst 38h			;001f
-	rst 38h			;0020
+	rst 38h			;0020  RST 20h -> RST 38h
 	rst 38h			;0021
 	rst 38h			;0022
 	rst 38h			;0023
@@ -35,7 +128,7 @@ displaymsg:
 	rst 38h			;0025
 	rst 38h			;0026
 	rst 38h			;0027
-	rst 38h			;0028
+	rst 38h			;0028  RST 28h -> RST 38h
 	rst 38h			;0029
 	rst 38h			;002a
 	rst 38h			;002b
@@ -43,7 +136,7 @@ displaymsg:
 	rst 38h			;002d
 	rst 38h			;002e
 	rst 38h			;002f
-	rst 38h			;0030
+	rst 38h			;0030  RST 30h -> RST 38h
 	rst 38h			;0031
 	rst 38h			;0032
 	rst 38h			;0033
@@ -51,7 +144,7 @@ displaymsg:
 	rst 38h			;0035
 	rst 38h			;0036
 	rst 38h			;0037
-	rst 38h			;0038
+	rst 38h			;0038  RST 38h - Common error handler
 	rst 38h			;0039
 	rst 38h			;003a
 	rst 38h			;003b
@@ -59,1415 +152,2002 @@ displaymsg:
 	rst 38h			;003d
 	rst 38h			;003e
 	rst 38h			;003f
-	jp l0000h		;0040
-	jp l0000h		;0043
+
+; ================================================================================
+; WARM BOOT AND RESTART VECTORS
+; ================================================================================
+
+	jp l0000h		;0040  Warm boot - restart system
+	jp l0000h		;0043  Another restart vector
+; ================================================================================
+; MAIN SYSTEM INITIALIZATION
+; ================================================================================
+; This routine initializes all I/O controllers and system hardware
+
 l_init:
-	out (0c0h),a		;0046 clear io, floppy control
-	out (0c4h),a		;0048 clear io,Program map A base
-	out (0c5h),a		;004a clear io,Program map B base
-	out (0c6h),a		;004c clear io,DMA map A base
-	out (0c7h),a		;004e clear io,DMA map B base
-	out (0d4h),a		;0050 clear io,Hi-res color
-	out (0d8h),a		;0052 clear io,Hi-res start
-	ld hl,PIOA_start		;0054
-	jp l0562h		;0057  do OTIR loop on following data 00562h
+	out (0c0h),a		;0046  Clear floppy disk controller
+	out (0c4h),a		;0048  Clear Program map A base address
+	out (0c5h),a		;004a  Clear Program map B base address  
+	out (0c6h),a		;004c  Clear DMA map A base address
+	out (0c7h),a		;004e  Clear DMA map B base address
+	out (0d4h),a		;0050  Clear Hi-res color control
+	out (0d8h),a		;0052  Clear Hi-res graphics start address
+	ld hl,PIOA_start	;0054  Point to I/O initialization data table
+	jp l0562h		;0057  Jump to OTIR routine to initialize peripherals
+
+; ================================================================================
+; I/O CONTROLLER INITIALIZATION DATA TABLE
+; ================================================================================
+; This table contains initialization sequences for various Z80 peripheral chips
+; Format: Port address, Count, Data bytes...
+; Used by OTIR routine at 0562h
 
 ; BLOCK 'PIOA' (start 0x005a end 0x008b)
 PIOA_start:
-	defb 0b5h		;005a io port CRT register select
-	defb 004h		;005b count 4
-	defb 0cfh		;005c
-	defb 0b8h		;005d
-	defb 037h		;005e
-	defb 0efh		;005f
-	;
-	defb 0b4h		;0060 io port PIO A data
-	defb 001h		;0061 count 1
-	defb 001h		;0062
-	;
-	defb 0a1h		;0063 io port DART A command
-	defb 006h		;0064 count 6
-	defb 048h		;0065
-	defb 048h		;0066
-	defb 004h		;0067
-	defb 044h		;0068
-	defb 005h		;0069
-	defb 0eah		;006a
-	;
-	defb 0a3h		;006b io port DART B command
-	defb 008h		;006c count 8
-	defb 048h		;006d
-	defb 048h		;006e
-	defb 004h		;006f
-	defb 044h		;0070
-	defb 001h		;0071
-	defb 000h		;0072
-	defb 003h		;0073
-	defb 0c1h		;0074
-	;
-	defb 0a5h		;0075 io port SIO A command
-	defb 002h		;0076 count 2
-	defb 048h		;0077
-	defb 048h		;0078
-	;
-	defb 0a7h		;0079 io port SIO B command
-	defb 002h		;007a count 2
-	defb 048h		;007b
-	defb 048h		;007c
-	;
-	defb 0a8h		;007d io port CTC CHANNEL 0 - Communications baud rate
-	defb 002h		;007e count 2
-	defb 003h		;007f
-	defb 003h		;0080
-	;
-	defb 0a9h		;0081 io port CTC CHANNEL 1 - AUX RS-232C baud rate
-	defb 002h		;0082 count 2
-	defb 003h		;0083
-	defb 003h		;0084
-	;
-	defb 0aah		;0085 io port  CTC CHANNEL 2 - Printer baud rate
-	defb 002h		;0086 count 2
-	defb 057h		;0087
-	defb 04eh		;0088
-	;
-	defb 000h		;0089 io port reset
-	defb 000h		;008a count 0 terminator
+	; CRT Controller initialization (6845 compatible)
+	defb 0b5h		;005a  I/O port: CRT register select
+	defb 004h		;005b  Count: 4 bytes to follow
+	defb 0cfh		;005c  Reg 0: Horizontal Total = 207+1=208 chars/line
+	defb 0b8h		;005d  Reg 1: Horizontal Displayed = 184 (likely 80 char mode with wide timing)
+	defb 037h		;005e  Reg 2: Horizontal Sync Position = 55 (after visible)
+	defb 0efh		;005f  Reg 3: Sync Width = V:14 lines, H:15 chars
+	
+	; PIO A Data Port
+	defb 0b4h		;0060  I/O port: PIO A data
+	defb 001h		;0061  Count: 1 byte to follow
+	defb 001h		;0062  Data: Enable something
+	
+	; DART A (Serial port A) initialization
+	defb 0a1h		;0063  I/O port: DART A command
+	defb 006h		;0064  Count: 6 bytes to follow
+	defb 048h		;0065  Reset command
+	defb 048h		;0066  Reset command (double reset)
+	defb 004h		;0067  Write register 4: Clock/format control
+	defb 044h		;0068  16x clock, 1 stop bit, no parity
+	defb 005h		;0069  Write register 5: Transmit control  
+	defb 0eah		;006a  DTR active, RTS active, Tx enable, 8 bits
+	
+	; DART B (Serial port B) initialization  
+	defb 0a3h		;006b  I/O port: DART B command
+	defb 008h		;006c  Count: 8 bytes to follow
+	defb 048h		;006d  Reset command
+	defb 048h		;006e  Reset command (double reset)
+	defb 004h		;006f  Write register 4: Clock/format control
+	defb 044h		;0070  16x clock, 1 stop bit, no parity
+	defb 001h		;0071  Write register 1: Interrupt control
+	defb 000h		;0072  No interrupts enabled
+	defb 003h		;0073  Write register 3: Receive control
+	defb 0c1h		;0074  Rx enable, 8 bits per char
+	
+	; SIO A (Serial I/O A) initialization
+	defb 0a5h		;0075  I/O port: SIO A command
+	defb 002h		;0076  Count: 2 bytes to follow
+	defb 048h		;0077  Reset command
+	defb 048h		;0078  Reset command (double reset)
+	
+	; SIO B (Serial I/O B) initialization
+	defb 0a7h		;0079  I/O port: SIO B command
+	defb 002h		;007a  Count: 2 bytes to follow
+	defb 048h		;007b  Reset command
+	defb 048h		;007c  Reset command (double reset)
+	
+	; CTC (Counter Timer Circuit) initialization
+	; Used to generate baud rate clocks for serial communications
+	
+	; CTC Channel 0 - Communications baud rate generator
+	defb 0a8h		;007d  I/O port: CTC CHANNEL 0
+	defb 002h		;007e  Count: 2 bytes to follow
+	defb 003h		;007f  Control: Timer mode, prescaler 16, auto-trigger
+	defb 003h		;0080  Time constant: 3 (high-speed rate)
+	
+	; CTC Channel 1 - Auxiliary RS-232C baud rate generator  
+	defb 0a9h		;0081  I/O port: CTC CHANNEL 1
+	defb 002h		;0082  Count: 2 bytes to follow
+	defb 003h		;0083  Control: Timer mode, prescaler 16, auto-trigger
+	defb 003h		;0084  Time constant: 3 (same rate as channel 0)
+	
+	; CTC Channel 2 - Printer baud rate generator
+	defb 0aah		;0085  I/O port: CTC CHANNEL 2
+	defb 002h		;0086  Count: 2 bytes to follow
+	defb 057h		;0087  Control: Timer mode, prescaler 256, auto-trigger
+	defb 04eh		;0088  Time constant: 78 (slower rate for printer)
+	
+	; End of I/O initialization table
+	defb 000h		;0089  Terminator: port 0 (invalid)
+	defb 000h		;008a  Terminator: count 0
+
 PIOA_end:
-	ld ix,initcontinue		;008b continuation addr 00092h
-	jp setupclearscreen		;008f setup display and clear screen  00505h
+	ld ix,initcontinue	;008b  Set continuation address after screen setup
+	jp setupclearscreen	;008f  Initialize display and clear screen
+
+; ================================================================================
+; INITIALIZATION CONTINUATION
+; ================================================================================
+; Returns here after display is initialized and cleared
+
 initcontinue:
-	ld a,080h		;0092
-	out (0d4h),a		;0094  out 0d4h,80h Hi-res color enable copy, buzzer off
-	ld de,displaymem		;0096 point to display upper left corner 03000h
-	ld hl,TESTING_start		;0099 point to message 0009fh
-	jp displaymsg		;009c go display message at HL 00011h
+	ld a,080h		;0092  Enable hi-res graphics, disable buzzer
+	out (0d4h),a		;0094  Write to hi-res color control register
+	ld de,displaymem	;0096  Point to start of display memory
+	ld hl,TESTING_start	;0099  Point to "Testing." message
+	jp displaymsg		;009c  Display the message
+
+; ================================================================================
+; "TESTING." MESSAGE DATA
+; ================================================================================
 
 ; BLOCK 'TESTING' (start 0x009f end 0x00a8)
 TESTING_start:
-	defb 008h		;009f 8 bytes "Testing."
-	defb 054h		;00a0
-	defb 065h		;00a1
-	defb 073h		;00a2
-	defb 074h		;00a3
-	defb 069h		;00a4
-	defb 06eh		;00a5
-	defb 067h		;00a6
-	defb 02eh		;00a7
+	defb 008h		;009f  Message length: 8 characters
+	defb 054h		;00a0  'T'
+	defb 065h		;00a1  'e'
+	defb 073h		;00a2  's'
+	defb 074h		;00a3  't'
+	defb 069h		;00a4  'i'
+	defb 06eh		;00a5  'n'
+	defb 067h		;00a6  'g'
+	defb 02eh		;00a7  '.'
 TESTING_end:
-	ld a,005h		;00a8
-	out (0a3h),a		;00aa DART B command
-	ld a,068h		;00ac
-	out (0a3h),a		;00ae  DART B command
-	ld a,0f0h		;00b0  ?????
-	out (0c8h),a		;00b2 Map and system control
-	ld ix,0c001h		;00b4
-	ld bc,00c5h		;00b8
-	ld d,nomemchecks		;00bb Start test memory bank (1-9), go to zero afterwards 009h
-	ld a,0a0h		;00bd Check if 256k memory or 128k
-	out (0c5h),a		;00bf Program map B base
-	ld (ix-001h),b		;00c1
-	dec b			;00c4
-	inc a			;00c5
-	out (0c5h),a		;00c6 Program map B base
-	ld (ix-001h),b		;00c8
-	dec a			;00cb
-	out (0c5h),a		;00cc Program map B base
-	ld b,(ix-001h)		;00ce
-	inc b			;00d1
-	jr z,skip256		;00d2 $+4 skip for start of memtest 
-	ld d,011h		;00d4
+; ================================================================================
+; MEMORY DETECTION AND TEST INITIALIZATION
+; ================================================================================
+; This section detects memory size (128K vs 256K) and sets up memory testing
+
+	ld a,005h		;00a8  DART B register 5 (transmit control)
+	out (0a3h),a		;00aa  Select register 5
+	ld a,068h		;00ac  Enable transmit, 7 bits, no break
+	out (0a3h),a		;00ae  Configure DART B transmit
+	ld a,0f0h		;00b0  Memory mapping control value
+	out (0c8h),a		;00b2  Set map and system control register
+	ld ix,0c001h		;00b4  Point to banked memory + 1 (0xC001)
+	ld bc,00c5h		;00b8  BC = 0x00C5 (memory map port in C)
+	ld d,nomemchecks	;00bb  D = 9 (number of memory banks to test)
+
+; Memory size detection routine
+	ld a,0a0h		;00bd  Test value for 256K detection
+	out (0c5h),a		;00bf  Set program map B base to 0xA0
+	ld (ix-001h),b		;00c1  Write test value (0x00) to 0xC000
+	dec b			;00c4  B = 0xFF
+	inc a			;00c5  A = 0xA1
+	out (0c5h),a		;00c6  Set program map B base to 0xA1  
+	ld (ix-001h),b		;00c8  Write 0xFF to 0xC000 in new bank
+	dec a			;00cb  A = 0xA0 (back to first bank)
+	out (0c5h),a		;00cc  Switch back to first bank
+	ld b,(ix-001h)		;00ce  Read back value from 0xC000
+	inc b			;00d1  Increment (0x00 becomes 0x01)
+	jr z,skip256		;00d2  If zero, we have 256K (0xFF+1=0x00)
+	ld d,011h		;00d4  If not zero, set to test 17 banks (256K)
+
 skip256:
-	ld b,d			;00d6
-	ld hl,memtesteval		;00d7  00122h
-	ld de,0000h		;00da
+	ld b,d			;00d6  B = number of banks to test
+	ld hl,memtesteval	;00d7  Point to memory test bank list
+	ld de,0000h		;00da  Clear error counters
+; ================================================================================
+; MAIN MEMORY TEST LOOP
+; ================================================================================
+; Tests each memory bank using rotating bit patterns
+
 beginmemtest:
-	outi		;00dd Switch memory map
-	jr z,memcmp		;00df
-	exx			;00e1
-	ld b,055h		;00e2  memory check  value
-	ld e,000h		;00e4
+	outi			;00dd  Switch memory bank: output (HL) to port C(0xC5), HL++, B--
+	jr z,memcmp		;00df  If B=0, all banks tested - check results
+	exx			;00e1  Switch to alternate register set
+	ld b,055h		;00e2  Start with test pattern 0x55 (01010101)
+	ld e,000h		;00e4  Clear local error accumulator
+
+; Test loop for current memory bank using rotating patterns  
 memtestloop:
-	ld hl,0c000h		;00e6  Start for membank that has been switch into
-	ld c,b			;00e9
+	ld hl,0c000h		;00e6  Start of current memory bank
+	ld c,b			;00e9  Copy test pattern to C
+
+; Write test pattern to entire 16K bank
 memtestwriteloop:
-	ld (hl),c			;00ea
-	rlc c		;00eb
-	inc l			;00ed
-	jr nz,memtestwriteloop		;00ee -4
-	rlc c		;00f0
-	inc h			;00f2
-	jr nz,memtestwriteloop		;00f3 -9
-	ld h,0c0h		;00f5
-	ld c,b			;00f7
+	ld (hl),c		;00ea  Write pattern to memory
+	rlc c			;00eb  Rotate pattern left (01010101 -> 10101010)
+	inc l			;00ed  Next byte (low address)
+	jr nz,memtestwriteloop	;00ee  Continue until L wraps to 0
+	rlc c			;00f0  Rotate pattern again for next page
+	inc h			;00f2  Next page (high address)
+	jr nz,memtestwriteloop	;00f3  Continue until H wraps to 0
+
+; Read back and verify test pattern
+	ld h,0c0h		;00f5  Reset to start of bank
+	ld c,b			;00f7  Restore original test pattern
+
 memtestreadloop:
-	ld a,(hl)			;00f8
-	xor c			;00f9
-	or e			;00fa
-	ld e,a			;00fb
-	rlc c		;00fc
-	inc l			;00fe
-	jr nz,memtestreadloop		;00ff
-	rlc c		;0101
-	inc h			;0103
-	jr nz,memtestreadloop		;0104
-	rlc b		;0106
-	jr nc,memtestloop		;0108
-	ld a,e			;010a
-	exx			;010b
-	and a			;010c
-	jr z,memgood		;010d
-	inc a			;010f
-	jr z,memerror		;0110
-	or d			;0112
-	ld d,a			;0113
-	jr memgood		;0114
+	ld a,(hl)		;00f8  Read memory location
+	xor c			;00f9  Compare with expected pattern
+	or e			;00fa  Accumulate errors in E
+	ld e,a			;00fb  Store error accumulator
+	rlc c			;00fc  Rotate expected pattern
+	inc l			;00fe  Next byte
+	jr nz,memtestreadloop	;00ff  Continue until L wraps
+	rlc c			;0101  Rotate pattern for next page
+	inc h			;0103  Next page  
+	jr nz,memtestreadloop	;0104  Continue until H wraps
+	rlc b			;0106  Rotate base pattern for next iteration
+	jr nc,memtestloop	;0108  Continue if not back to original (8 patterns)
+
+; Process test results for this bank
+	ld a,e			;010a  Get error accumulator
+	exx			;010b  Switch back to main register set
+	and a			;010c  Test for errors
+	jr z,memgood		;010d  No errors - bank is good
+	inc a			;010f  Check if all bits failed (0xFF -> 0x00)
+	jr z,memerror		;0110  Complete failure - count as bad bank
+	or d			;0112  Partial failure - OR with global error flags
+	ld d,a			;0113  Store combined error status
+	jr memgood		;0114  Continue testing
+
 memerror:
-	inc e			;0116
+	inc e			;0116  Increment bad bank counter
+
 memgood:
-	ld a,b			;0117
-	cp 004h		;0118
-	jr nz,beginmemtest		;011a
-	ld a,020h		;011c
-	out (0c0h),a		;011e  Floppy external control Motor on!
-	jr beginmemtest		;0120
-memtesteval:		;Memory ports
-	defb 0a1h		;0122 count 16
-	defb 0c1h		;0123
-	defb 0e1h		;0124
-	defb 000h		;0125
-	defb 020h		;0126
-	defb 040h		;0127
-	defb 060h		;0128
-	defb 080h		;0129
-	defb 0a0h		;012a //Start of 256kB memtest
-	defb 0c0h		;012b
-	defb 0e0h		;012c
-	defb 001h		;012d
-	defb 021h		;012e
-	defb 041h		;012f
-	defb 061h		;0130
-	defb 081h		;0131
-	nop				;0132
+	ld a,b			;0117  Check remaining bank count
+	cp 004h			;0118  Is this bank 4?
+	jr nz,beginmemtest	;011a  If not bank 4, continue testing
+	ld a,020h		;011c  FDC control: Drive B select (dual drive system)
+	out (0c0h),a		;011e  Write to floppy controller control register
+	jr beginmemtest		;0120  Continue memory testing
+; ================================================================================
+; MEMORY BANK SELECTION TABLE
+; ================================================================================
+; This table contains the bank values written to port 0xC5 (Program map B base)
+; Each value maps a different 16K memory bank into the 0xC000-0xFFFF address space
+
+memtesteval:		; Memory bank mapping values
+	defb 0a1h		;0122  Bank count: 161 (actually used as counter)
+	defb 0c1h		;0123  Memory bank 0xC1
+	defb 0e1h		;0124  Memory bank 0xE1  
+	defb 000h		;0125  Memory bank 0x00
+	defb 020h		;0126  Memory bank 0x20
+	defb 040h		;0127  Memory bank 0x40
+	defb 060h		;0128  Memory bank 0x60
+	defb 080h		;0129  Memory bank 0x80
+	defb 0a0h		;012a  Memory bank 0xA0 (Start of 256KB test range)
+	defb 0c0h		;012b  Memory bank 0xC0
+	defb 0e0h		;012c  Memory bank 0xE0
+	defb 001h		;012d  Memory bank 0x01
+	defb 021h		;012e  Memory bank 0x21
+	defb 041h		;012f  Memory bank 0x41
+	defb 061h		;0130  Memory bank 0x61
+	defb 081h		;0131  Memory bank 0x81
+; ================================================================================
+; MEMORY TEST RESULTS EVALUATION
+; ================================================================================
+; Check if memory test found any errors and decide next action
+nop
 memcmp:
-	xor a			;0133
-	or d			;0134
-	or e			;0135 Any errors?
-	jr z,floppystart		;0136
-	ld ix,memcheckdisplay		;0138
-	jp setupcrt		;013c
+	xor a			;0133  Clear A register
+	or d			;0134  Check global error flags in D
+	or e			;0135  Check bad bank count in E - Any errors?
+	jr z,floppystart	;0136  If no errors, proceed to floppy boot
+	ld ix,memcheckdisplay	;0138  Memory errors found - prepare error display
+	jp setupcrt		;013c  Jump to CRT setup for error display
+
+; ================================================================================
+; MEMORY ERROR DISPLAY ROUTINE
+; ================================================================================
+
 memcheckdisplay:
-	ld de,displaymem		;013f
-	ld hl,ERROR2_start		;0142
-	jp displaymsg		;0145
+	ld de,displaymem	;013f  Point to display memory
+	ld hl,ERROR2_start	;0142  Point to error message
+	jp displaymsg		;0145  Display "Error #2 :Call service."
+
+; ================================================================================
+; ERROR #2 MESSAGE DATA
+; ================================================================================
 
 ; BLOCK 'ERROR2' (start 0x0148 end 0x0160)
 ERROR2_start:
-	defb 017h		;0148 count 23
-	defb 045h		;0149 Error #2 :Call service.
-	defb 072h		;014a
-	defb 072h		;014b
-	defb 06fh		;014c
-	defb 072h		;014d
-	defb 020h		;014e
-	defb 023h		;014f
-	defb 032h		;0150
-	defb 020h		;0151
-	defb 03ah		;0152
-	defb 043h		;0153
-	defb 061h		;0154
-	defb 06ch		;0155
-	defb 06ch		;0156
-	defb 020h		;0157
-	defb 073h		;0158
-	defb 065h		;0159
-	defb 072h		;015a
-	defb 076h		;015b
-	defb 069h		;015c
-	defb 063h		;015d
-	defb 065h		;015e
-	defb 02eh		;015f
+	defb 017h		;0148  Message length: 23 characters
+	defb 045h		;0149  'E' - "Error #2 :Call service."
+	defb 072h		;014a  'r'
+	defb 072h		;014b  'r'
+	defb 06fh		;014c  'o'
+	defb 072h		;014d  'r'
+	defb 020h		;014e  ' '
+	defb 023h		;014f  '#'
+	defb 032h		;0150  '2'
+	defb 020h		;0151  ' '
+	defb 03ah		;0152  ':'
+	defb 043h		;0153  'C'
+	defb 061h		;0154  'a'
+	defb 06ch		;0155  'l'
+	defb 06ch		;0156  'l'
+	defb 020h		;0157  ' '
+	defb 073h		;0158  's'
+	defb 065h		;0159  'e'
+	defb 072h		;015a  'r'
+	defb 076h		;015b  'v'
+	defb 069h		;015c  'i'
+	defb 063h		;015d  'c'
+	defb 065h		;015e  'e'
+	defb 02eh		;015f  '.'
 ERROR2_end:
-	halt			;0160
+	halt			;0160  System halt - requires service intervention
+; ================================================================================
+; FLOPPY DISK BOOT INITIALIZATION  
+; ================================================================================
+; Memory test passed - prepare for floppy disk boot
+
 floppystart:
-	out (0c5h),a		;0161 Program map B base
-	out (0c8h),a		;0163 Map and system control
-	dec hl			;0165
-	dec hl			;0166
-	ld a,(hl)			;0167
+	out (0c5h),a		;0161  Clear program map B base (A=0 from memcmp)
+	out (0c8h),a		;0163  Clear map and system control (disable banking)
+	dec hl			;0165  HL was pointing past end of memory test table
+	dec hl			;0166  Move back to get the memory size indicator
+	ld a,(hl)		;0167  Load memory configuration value
+
 floppystart2:
-	rrca			;0168
-	and 080h		;0169
-	ld (0ff80h),a		;016b
-	ld de,0ffa6h		;016e
-	ld hl,005beh		;0171
-	ld bc,0005ah		;0174
-	ldir		;0177
-	call setupclearscreen2		;0179
+	rrca			;0168  Rotate right with carry to get MSB
+	and 080h		;0169  Isolate bit 7 (128K vs 256K indicator)
+	ld (0ff80h),a		;016b  Store memory size flag: 0x80=256K, 0x00=128K
+	ld de,0ffa6h		;016e  Destination: high RAM workspace area
+	ld hl,005beh		;0171  Source: ROM data block at 0x05BE
+	ld bc,0005ah		;0174  Count: 90 bytes of runtime data
+	ldir			;0177  Copy ROM constants to RAM workspace
+	call setupclearscreen2	;0179  Clear screen and setup display for boot
+; ================================================================================
+; DISK BOOT SEQUENCE WITH AUTO-RETRY
+; ================================================================================
+; ================================================================================
+; BOOT DEVICE DETECTION AND PRIORITY SYSTEM
+; ================================================================================
+; Memory initialization complete - attempt to boot with device auto-detection
+; 
+; BOOT PRIORITY ORDER:
+; 1. Auto-detect controller type (port 0xFF) to determine available devices
+; 2. If hard disk detected: Try hard disk FIRST (faster, larger capacity)
+; 3. If hard disk fails or not present: Fall back to floppy disk drives
+; 4. Try drives in order: Drive 0, 1, 2, 3 (up to 8 total attempts)
+
 readydiskloop:
-	call readydisk		;017c
-	call sub_061ch		;017f
-	ld a,0ffh		;0182
-	jr c,skipinvert		;0184
-	cpl			;0186
+	call readydisk		;017c  Display "Ready For System Disk" message
+	call sub_061ch		;017f  *** CRITICAL *** Initialize disk controller & detect HDD vs floppy
+	ld a,0ffh		;0182  Load 0xFF (default retry flag)
+	jr c,skipinvert		;0184  Keep 0xFF if carry set (controller error - floppy only mode)
+	cpl			;0186  Invert to 0x00 (normal operation - HDD detection successful)
 skipinvert:
-	ld (0ff93h),a		;0187
-	ld hl,00404h		;018a
-	ld (0ff91h),hl		;018d
-	or a			;0190
-	jr nz,l01c3h		;0191
-	ld c,010h		;0193
-	call sub_065ah		;0195
-	jr c,l01abh		;0198
-	ld bc,00000h		;019a
-	call sub_040eh		;019d
-	jr c,l01abh		;01a0
-	call sub_03a2h		;01a2
-	ld a,(0ff8bh)		;01a5
-	ld (0ff91h),a		;01a8
+	ld (0ff93h),a		;0187  Store boot device mode: 0xFF=floppy-only, 0x00=HDD+floppy available
+	ld hl,00404h		;018a  H=4 retries, L=4 track number?
+	ld (0ff91h),hl		;018d  Store retry count and track parameters
+	or a			;0190  Test the boot device mode flag
+	jr nz,l01c3h		;0191  If floppy-only mode (0xFF), skip HDD attempts, go to drive loop
+	
+	; *** HARD DISK BOOT ATTEMPTS (when HDD controller detected) ***
+	; Normal boot mode: Try hard disk operations FIRST
+	ld c,010h		;0193  Hard disk command 0x10 (seek track 0/recalibrate)
+	call sub_065ah		;0195  Execute hard disk command through DMA
+	jr c,l01abh		;0198  If HDD error, try alternate HDD command
+	ld bc,00000h		;019a  B=drive 0, C=track 0 (hard disk drive 0)
+	call sub_040eh		;019d  Attempt to read boot sector from hard disk
+	jr c,l01abh		;01a0  If HDD read error, try alternate HDD approach
+	call sub_03a2h		;01a2  Process successful HDD sector read
+	ld a,(0ff8bh)		;01a5  Get boot validation result from HDD
+	ld (0ff91h),a		;01a8  Store HDD boot result
+
 l01abh:
-	ld c,011h		;01ab
-	call sub_065ah		;01ad
-	jr c,l01c3h		;01b0
-	ld bc,0000h		;01b2
-	call sub_040eh		;01b5
-	jr c,l01c3h		;01b8
-	call sub_03a2h		;01ba
-	ld a,(0ff8bh)		;01bd
-	ld (0ff92h),a		;01c0
+	; *** ALTERNATE HARD DISK ATTEMPT ***
+	ld c,011h		;01ab  Hard disk command 0x11 (alternate seek/step command)
+	call sub_065ah		;01ad  Execute alternate hard disk command through DMA
+	jr c,l01c3h		;01b0  If HDD command error, fall back to floppy drives
+	ld bc,0000h		;01b2  B=drive 0, C=track 0 (hard disk drive 0)  
+	call sub_040eh		;01b5  Second attempt to read HDD boot sector
+	jr c,l01c3h		;01b8  If HDD read still fails, fall back to floppy drives
+	call sub_03a2h		;01ba  Process successful HDD sector read
+	ld a,(0ff8bh)		;01bd  Get final HDD boot validation result
+	ld (0ff92h),a		;01c0  Store HDD boot result flag
+
+; ================================================================================
+; FLOPPY DRIVE FALLBACK AND DRIVE SELECTION LOOP
+; ================================================================================
+; Reached when: 1) Hard disk not detected, 2) Hard disk boot failed, or 3) Force floppy mode
+; Systematically tries all floppy drives (0-3) with multiple retry attempts
+
 l01c3h:
-	ld a,001h		;01c3
-	ld c,008h		;01c5
+	ld a,001h		;01c3  Start with drive bit 0 (will create drive ID 0xA1)
+	ld c,008h		;01c5  Retry counter: 8 attempts across all floppy drives
+
+driveloop:
 l01c7h:
-	or 0a0h		;01c7
-	out (0c0h),a		;01c9 Floppy external control
-	ld b,a			;01cb
+	; *** FLOPPY DRIVE SELECTION ***
+	; Drive encoding: 0xA1=Drive 0, 0xA2=Drive 1, 0xA4=Drive 2, 0xA8=Drive 3
+	or 0a0h			;01c7  OR with 0xA0 base: creates floppy controller commands
+	out (0c0h),a		;01c9  Select floppy drive via port 0xC0 (different from HDD ports 0x78-0x7B)
+	ld b,a			;01cb  Save current drive select value
+
+; Wait for floppy drive ready status
 l01cch:
-	in a,(0b0h)		;01cc Floppy status
-	rr a		;01ce
-	jr c,l01cch		;01d0
-	in a,(0b0h)		;01d2 Floppy status
-	add a,a			;01d4
-	jr c,l01ddh		;01d5
-	call delayloop		;01d7
-	call loadingdisk		;01da
+	in a,(0b0h)		;01cc  Read floppy controller status register (port 0xB0, not HDD 0x79)
+	rr a			;01ce  Rotate right - check busy bit (bit 0) into carry
+	jr c,l01cch		;01d0  Loop while floppy drive is busy (bit 0 = 1)
+	in a,(0b0h)		;01d2  Read floppy status again
+	add a,a			;01d4  Shift left - check ready bit (bit 7) into carry  
+	jr c,l01ddh		;01d5  If floppy drive ready (bit 7 = 1), continue to next drive
+	call delayloop		;01d7  Floppy drive not ready - wait a bit
+	call loadingdisk	;01da  Display "Loading..." and attempt boot from this floppy drive
+
+; *** DRIVE ADVANCEMENT AND RETRY LOGIC ***
 l01ddh:
-	inc c			;01dd
-	ld a,b			;01de
-	add a,a			;01df
-	and 00fh		;01e0
-	jr nz,l01c7h		;01e2
-	ld a,(0ff93h)		;01e4
-	or a			;01e7
-	jr nz,l0204h		;01e8
-	in a,(0ffh)		;01ea  ????
-	and 020h		;01ec
-	jr nz,l0204h		;01ee
-	ld c,010h		;01f0
-	call sub_065ah		;01f2
-	ld b,000h		;01f5
-	call nc,loadingdisk		;01f7
-	ld c,011h		;01fa
-	call sub_065ah		;01fc
-	ld b,000h		;01ff
-	call nc,loadingdisk		;0201
+	inc c			;01dd  Increment attempt counter (8 total attempts across all drives)
+	ld a,b			;01de  Restore drive select value from previous iteration
+	add a,a			;01df  Shift left to advance to next drive: 0xA1->0xA2->0xA4->0xA8
+	and 00fh		;01e0  Mask to keep only drive bits (removes 0xA0 base, leaves 1,2,4,8)
+	jr nz,l01c7h		;01e2  Continue loop if more drives to try (bits 1,2,4,8 not all exhausted)
+	
+; ================================================================================
+; ALL FLOPPY DRIVES EXHAUSTED - FINAL FALLBACK ATTEMPTS
+; ================================================================================
+; Reached when all floppy drives 0-3 have been tried and failed to boot
+	
+	ld a,(0ff93h)		;01e4  Load boot mode flag from memory
+	or a			;01e7  Test if normal boot mode (0x00) or retry mode (0xFF)
+	jr nz,l0204h		;01e8  If already in retry mode, skip to "No System Device" error
+	in a,(0ffh)		;01ea  Read hardware status port 0xFF (same port used for HDD detection)
+	and 020h		;01ec  Check bit 5 - unknown hardware condition/status
+	jr nz,l0204h		;01ee  If bit 5 set, skip directly to error message
+	
+; *** DESPERATE FINAL ATTEMPTS ON DRIVE 0 ONLY ***
+; Special recovery commands specifically for Drive 0 as last resort
+	ld c,010h		;01f0  Load floppy command 0x10 (likely recalibrate/restore)
+	call sub_065ah		;01f2  Execute floppy controller command
+	ld b,000h		;01f5  Force selection of Drive 0 specifically  
+	call nc,loadingdisk	;01f7  If command succeeded (no carry), try loading from Drive 0
+	ld c,011h		;01fa  Load floppy command 0x11 (likely seek home/step in)
+	call sub_065ah		;01fc  Execute second recovery command
+	ld b,000h		;01ff  Force Drive 0 selection again
+	call nc,loadingdisk	;0201  If command succeeded, make final boot attempt from Drive 0
+
+; ================================================================================
+; BOOT FAILURE - DISPLAY ERROR AND RESTART BOOT SEQUENCE  
+; ================================================================================
+
 l0204h:
-	call setupclearscreen2		;0204
-	ld bc,002a3h		;0207
-	ld hl,0061ah		;020a
-	otir		;020d
-	ld de,03000h		;020f
-	ld hl,NOSYSTEM_start		;0212
-	jp displaymsg		;0215
+	call setupclearscreen2	;0204  Clear screen and setup display for error
+	ld bc,002a3h		;0207  B=2 bytes, C=0xA3 port (memory control?)
+	ld hl,0061ah		;020a  Source: ROM data at 0x061A
+	otir			;020d  Output 2 bytes to port 0xA3 (setup display controller)
+	ld de,03000h		;020f  Display memory base address  
+	ld hl,NOSYSTEM_start	;0212  Point to "No System Device On Line." message
+	jp displaymsg		;0215  Display error message and wait
+
+; ================================================================================
+; "NO SYSTEM DEVICE ON LINE" MESSAGE AND RETRY LOOP
+; ================================================================================
 
 ; BLOCK 'NOSYSTEM' (start 0x0218 end 0x0232)
 NOSYSTEM_start:
-	defb 019h		;0218 count 25
-	defb 04eh		;0219 No System Device On Line.
-	defb 06fh		;021a
-	defb 020h		;021b
-	defb 053h		;021c
-	defb 079h		;021d
-	defb 073h		;021e
-	defb 074h		;021f
-	defb 065h		;0220
-	defb 06dh		;0221
-	defb 020h		;0222
-	defb 044h		;0223
-	defb 065h		;0224
-	defb 076h		;0225
-	defb 069h		;0226
-	defb 063h		;0227
-	defb 065h		;0228
-	defb 020h		;0229
-	defb 04fh		;022a
-	defb 06eh		;022b
-	defb 020h		;022c
-	defb 04ch		;022d
-	defb 069h		;022e
-	defb 06eh		;022f
-	defb 065h		;0230
-	defb 02eh		;0231
+	defb 019h		;0218  Message length: 25 characters
+	defb 04eh		;0219  'N' - "No System Device On Line."
+	defb 06fh		;021a  'o'
+	defb 020h		;021b  ' '
+	defb 053h		;021c  'S'
+	defb 079h		;021d  'y'
+	defb 073h		;021e  's'
+	defb 074h		;021f  't'
+	defb 065h		;0220  'e'
+	defb 06dh		;0221  'm'
+	defb 020h		;0222  ' '
+	defb 044h		;0223  'D'
+	defb 065h		;0224  'e'
+	defb 076h		;0225  'v'
+	defb 069h		;0226  'i'
+	defb 063h		;0227  'c'
+	defb 065h		;0228  'e'
+	defb 020h		;0229  ' '
+	defb 04fh		;022a  'O'
+	defb 06eh		;022b  'n'
+	defb 020h		;022c  ' '
+	defb 04ch		;022d  'L'
+	defb 069h		;022e  'i'
+	defb 06eh		;022f  'n'
+	defb 065h		;0230  'e'
+	defb 02eh		;0231  '.'
 NOSYSTEM_end:
-	call delayloop		;0232
-	call delayloop		;0235
-	call delayloop		;0238
-	jp readydiskloop		;023b
+	call delayloop		;0232  Wait for user to see message (~1 second)
+	call delayloop		;0235  Additional delay (~1 second)  
+	call delayloop		;0238  Final delay (~1 second, total ~3 seconds)
+	jp readydiskloop	;023b  Restart entire boot sequence - infinite retry loop!
+
+; ================================================================================
+; CRITICAL ERROR HANDLER - SYSTEM HALT
+; ================================================================================
+; This routine is called for fatal hardware errors that require service
+
 l023eh:
-	ld ix,returnsetupcrt1		;023e
-	jp setupcrt		;0242
+	ld ix,returnsetupcrt1	;023e  Setup return address for CRT initialization
+	jp setupcrt		;0242  Initialize CRT controller and return here
+
 returnsetupcrt1:
-	call screenclearnetry2		;0245
-	rst 10h			;0248
+	call screenclearnetry2	;0245  Clear screen and setup for error display
+	rst 10h			;0248  RST 10h: Display message routine
+
+; ================================================================================
+; ERROR #0 MESSAGE DATA  
+; ================================================================================
 
 ; BLOCK 'ERROR0' (start 0x0249 end 0x0261)
 ERROR0_start:
-	defb 017h		;0249 count 23
-	defb 045h		;024a Error #0: Call service.
-	defb 072h		;024b
-	defb 072h		;024c
-	defb 06fh		;024d
-	defb 072h		;024e
-	defb 020h		;024f
-	defb 023h		;0250
-	defb 030h		;0251
-	defb 03ah		;0252
-	defb 020h		;0253
-	defb 043h		;0254
-	defb 061h		;0255
-	defb 06ch		;0256
-	defb 06ch		;0257
-	defb 020h		;0258
-	defb 073h		;0259
-	defb 065h		;025a
-	defb 072h		;025b
-	defb 076h		;025c
-	defb 069h		;025d
-	defb 063h		;025e
-	defb 065h		;025f
-	defb 02eh		;0260
+	defb 017h		;0249  Message length: 23 characters
+	defb 045h		;024a  'E' - "Error #0: Call service."
+	defb 072h		;024b  'r'
+	defb 072h		;024c  'r'
+	defb 06fh		;024d  'o'
+	defb 072h		;024e  'r'
+	defb 020h		;024f  ' '
+	defb 023h		;0250  '#'
+	defb 030h		;0251  '0'
+	defb 03ah		;0252  ':'
+	defb 020h		;0253  ' '
+	defb 043h		;0254  'C'
+	defb 061h		;0255  'a'
+	defb 06ch		;0256  'l'
+	defb 06ch		;0257  'l'
+	defb 020h		;0258  ' '
+	defb 073h		;0259  's'
+	defb 065h		;025a  'e'
+	defb 072h		;025b  'r'
+	defb 076h		;025c  'v'
+	defb 069h		;025d  'i'
+	defb 063h		;025e  'c'
+	defb 065h		;025f  'e'
+	defb 02eh		;0260  '.'
 ERROR0_end:
-	halt			;0261
+	halt			;0261  System halt - requires service call
+; ================================================================================
+; DISK LOADING ROUTINE - MAIN BOOT SECTOR LOADER
+; ================================================================================
+; This routine displays "Loading" message and attempts to load the boot sector
+; Input: B = drive number (0-3)
+; Uses: All registers, modifies disk parameters at 0xFF81-0xFF82
+
 loadingdisk:
-	push bc			;0262
-	xor a			;0263
-	ld (0ff81h),a		;0264
-	ld (0ff82h),a		;0267
-	rst 8			;026a
+	push bc			;0262  Save BC (drive number and parameters)
+	xor a			;0263  Clear A register (A = 0)
+	ld (0ff81h),a		;0264  Clear disk status parameter 1
+	ld (0ff82h),a		;0267  Clear disk status parameter 2  
+	rst 8			;026a  RST 8: Display message routine
+
+; ================================================================================
+; "LOADING " MESSAGE DATA
+; ================================================================================
 
 ; BLOCK 'LOADING' (start 0x026b end 0x0274)
 LOADING_start:
-	defb 008h		;026b count 8
-	defb 04ch		;026c Loading 
-	defb 06fh		;026d
-	defb 061h		;026e
-	defb 064h		;026f
-	defb 069h		;0270
-	defb 06eh		;0271
-	defb 067h		;0272
-	defb 020h		;0273
+	defb 008h		;026b  Message length: 8 characters
+	defb 04ch		;026c  'L' - "Loading "
+	defb 06fh		;026d  'o'
+	defb 061h		;026e  'a'
+	defb 064h		;026f  'd'
+	defb 069h		;0270  'i'
+	defb 06eh		;0271  'n'
+	defb 067h		;0272  'g'
+	defb 020h		;0273  ' '
 LOADING_end:
-	pop ix		;0274
-	call sub_04a1h		;0276
-	jr c,l023eh		;0279
-	ld bc,0000h		;027b
-	call sub_040eh		;027e
-	jr c,l02ddh		;0281
-	ld hl,(0ff81h)		;0283
-	ld a,l			;0286
-	and a			;0287
-	jr z,l029ch		;0288
-	ld a,h			;028a
-	and 003h		;028b
-	in a,(0ffh)		;028d
-	jr z,l0298h		;028f
-	bit 0,a		;0291
-	jr nz,l029ch		;0293
+	pop ix			;0274  Restore IX from stack (return address)
+	call sub_04a1h		;0276  Initialize disk controller and seek to track 0
+	jr c,l023eh		;0279  If seek error, jump to fatal error handler
+	ld bc,0000h		;027b  B=track 0, C=sector 0 (boot sector location)
+	call sub_040eh		;027e  Read boot sector from disk
+	jr c,l02ddh		;0281  If read error, handle disk error
+	
+	; Check disk status and system configuration
+	ld hl,(0ff81h)		;0283  Load disk status parameters (2 bytes)
+	ld a,l			;0286  Get low byte of status
+	and a			;0287  Test if zero (no special conditions)
+	jr z,l029ch		;0288  If zero, continue with normal boot process
+	ld a,h			;028a  Get high byte of status  
+	and 003h		;028b  Mask bits 0-1 (configuration bits)
+	in a,(0ffh)		;028d  Read system status port 0xFF
+	jr z,l0298h		;028f  If masked value is zero, check bit 1
+	bit 0,a			;0291  Test bit 0 of system status
+	jr nz,l029ch		;0293  If bit 0 set, continue normal boot
 l0295h:
-	jp l034bh		;0295
+	jp l034bh		;0295  Jump to alternate boot routine
+
 l0298h:
-	bit 1,a		;0298
-	jr z,l0295h		;029a
+	bit 1,a			;0298  Test bit 1 of system status
+	jr z,l0295h		;029a  If bit 1 clear, jump to alternate boot routine
+
 l029ch:
-	call sub_03a2h		;029c
-	jp c,l0343h		;029f
-	jr z,l02b6h		;02a2
-	call sub_040eh		;02a4
-	jr c,l02ddh		;02a7
-	ld hl,0401fh		;02a9
-	bit 0,(hl)		;02ac
-	jp nz,l034fh		;02ae
-	call sub_040eh		;02b1
-	jr c,l02ddh		;02b4
+	call sub_03a2h		;029c  Process and validate boot sector data
+	jp c,l0343h		;029f  If validation failed (carry set), handle error
+	jr z,l02b6h		;02a2  If zero flag set, skip additional sector read
+	call sub_040eh		;02a4  Read additional sector data if needed
+	jr c,l02ddh		;02a7  If read error, handle disk error
+
+; ================================================================================
+; BOOT SECTOR VALIDATION AND EXECUTION SETUP
+; ================================================================================
+; Boot sector successfully read - now validate and prepare for execution
+
+	ld hl,0401fh		;02a9  Point to boot sector signature/validity location
+	bit 0,(hl)		;02ac  Check boot sector validity bit 0
+	jp nz,l034fh		;02ae  If validity bit set, handle invalid boot sector
+	call sub_040eh		;02b1  Read final sector data if needed
+	jr c,l02ddh		;02b4  If read error, handle disk error
+
 l02b6h:
-	exx			;02b6
-	ld hl,0400eh		;02b7
-	ld d,(hl)			;02ba
-	inc hl			;02bb
-	ld e,(hl)			;02bc
-	push de			;02bd
-	pop iy		;02be
-	ld hl,04080h		;02c0
-	ld c,(hl)			;02c3
-	inc hl			;02c4
-	inc hl			;02c5
-	ld d,(hl)			;02c6
-	inc hl			;02c7
-	ld e,(hl)			;02c8
-	inc hl			;02c9
-	ld a,(hl)			;02ca
-	inc hl			;02cb
-	ld l,(hl)			;02cc
-	ld h,a			;02cd
-	ex de,hl			;02ce
-	push hl			;02cf
-	ld a,e			;02d0
-	add a,0ffh		;02d1
-	ld a,d			;02d3
-	exx			;02d4
-	ld e,000h		;02d5
-	adc a,e			;02d7
-	ld d,a			;02d8
-	pop hl			;02d9
-	call sub_0414h		;02da
+	exx			;02b6  Switch to alternate register set (BC',DE',HL')
+	ld hl,0400eh		;02b7  Point to boot program load address in boot sector
+	ld d,(hl)		;02ba  Get high byte of load address
+	inc hl			;02bb  Move to next byte
+	ld e,(hl)		;02bc  Get low byte of load address  
+	push de			;02bd  Save complete load address
+	pop iy			;02be  IY = target load address for boot program
+	ld hl,04080h		;02c0  Point to boot sector parameter block
+	ld c,(hl)		;02c3  Get boot parameter 1
+	inc hl			;02c4  Skip reserved byte
+	inc hl			;02c5  Point to next parameter
+	ld d,(hl)		;02c6  Get parameter high byte
+	inc hl			;02c7  Move to next
+	ld e,(hl)		;02c8  Get parameter low byte
+	inc hl			;02c9  Move to next
+	ld a,(hl)		;02ca  Get additional parameter byte
+	inc hl			;02cb  Move to final parameter  
+	ld l,(hl)		;02cc  Get final parameter byte
+	ld h,a			;02cd  Combine A and L into HL
+	ex de,hl		;02ce  Exchange DE and HL registers
+	push hl			;02cf  Save HL on stack
+	ld a,e			;02d0  Get low byte for calculation
+	add a,0ffh		;02d1  Add 255 (effectively subtract 1 with carry)
+	ld a,d			;02d3  Get high byte
+	exx			;02d4  Switch back to main register set
+	ld e,000h		;02d5  E = 0 for addition
+	adc a,e			;02d7  Add high byte with carry from previous operation
+	ld d,a			;02d8  D = calculated high byte for sector loading
+	pop hl			;02d9  Restore HL from stack (boot program parameters)
+	call sub_0414h		;02da  Load complete boot program from disk into memory
+
+; ================================================================================
+; BOOT PROGRAM EXECUTION AND TRANSFER OF CONTROL
+; ================================================================================
+; Boot program successfully loaded - now transfer control to the loaded code
+
 l02ddh:
-	jr c,l0347h		;02dd
-	ld a,(0ff8bh)		;02df
-	cp 002h		;02e2
-	jr z,l02eeh		;02e4
-	xor a			;02e6
-	ex af,af'			;02e7
-	exx			;02e8
-	jp 0ffa6h		;02e9
+	jr c,l0347h		;02dd  If disk load error (carry set), handle error
+	ld a,(0ff8bh)		;02df  Get boot completion status flag
+	cp 002h			;02e2  Check if status = 2 (special boot mode)
+	jr z,l02eeh		;02e4  If special mode, use alternate execution path
+	
+	; Standard boot execution: Transfer control to loaded program
+	xor a			;02e6  Clear A register (A = 0)
+	ex af,af'		;02e7  Save AF to alternate AF' register 
+	exx			;02e8  Switch to alternate register set
+	jp 0ffa6h		;02e9  *** TRANSFER CONTROL TO LOADED BOOT PROGRAM! ***
+
+; ================================================================================
+; ALTERNATE BOOT EXECUTION PATH
+; ================================================================================
+; Special boot mode handling (status = 2)
+
 l02ech:
-	ex af,af'			;02ec
-	adc a,c			;02ed
+	ex af,af'		;02ec  Restore AF from alternate register
+	adc a,c			;02ed  Add C with carry for parameter processing
+
 l02eeh:
-	push ix		;02ee
-	pop bc			;02f0
-	ld a,(0ff8bh)		;02f1
-	ld de,00013h		;02f4
-	ld hl,0ff8dh		;02f7
-	jr nz,l033fh		;02fa
-	cp 002h		;02fc
-	jp nz,0ffb8h		;02fe
-	push bc			;0301
-	bit 3,c		;0302
-	jr nz,l030bh		;0304
-	ld a,0ffh		;0306
-	ld (0ff81h),a		;0308
+	push ix			;02ee  Save IX register (return address)
+	pop bc			;02f0  BC = return address from IX
+	ld a,(0ff8bh)		;02f1  Get boot completion status flag
+	ld de,00013h		;02f4  DE = 0x0013 (parameter constant)
+	ld hl,0ff8dh		;02f7  HL = system parameter storage area
+	jr nz,l033fh		;02fa  If status not zero, jump to error 0x33
+	cp 002h			;02fc  Compare status with 2 (special boot mode)
+	jp nz,0ffb8h		;02fe  If not 2, jump to alternate boot entry point
+	
+	; Special boot mode (status = 2) - setup system parameters
+	push bc			;0301  Save return address
+	bit 3,c			;0302  Test bit 3 of return address low byte
+	jr nz,l030bh		;0304  If bit 3 set, skip disk flag setup
+	ld a,0ffh		;0306  Set disk parameter flag
+	ld (0ff81h),a		;0308  Store at disk parameter location
+
 l030bh:
-	in a,(0ffh)		;030b
-	ld c,a			;030d
-	xor a			;030e
-	bit 0,c		;030f
-	jr z,l0315h		;0311
-	ld a,00fh		;0313
+	in a,(0ffh)		;030b  Read system status port 0xFF
+	ld c,a			;030d  Save status in C
+	xor a			;030e  Clear A register (A = 0)
+	bit 0,c			;030f  Test bit 0 of system status
+	jr z,l0315h		;0311  If bit 0 clear, skip
+	ld a,00fh		;0313  Set A = 0x0F (enable low nibble)
+
 l0315h:
-	bit 1,c		;0315
-	jr z,l031bh		;0317
-	or 0f0h		;0319
+	bit 1,c			;0315  Test bit 1 of system status
+	jr z,l031bh		;0317  If bit 1 clear, skip
+	or 0f0h			;0319  Set high nibble (A |= 0xF0)
+
 l031bh:
-	ld b,a			;031b
-	ld a,(0ff81h)		;031c
-	cpl			;031f
-	and a			;0320
-	jr z,l0334h		;0321
-	push bc			;0323
-	push ix		;0324
-	pop bc			;0326
-	ld a,c			;0327
-	sub 007h		;0328
-	ld b,a			;032a
-	ld a,080h		;032b
+	ld b,a			;031b  B = combined system configuration mask
+	ld a,(0ff81h)		;031c  Get disk parameter flag
+	cpl			;031f  Complement (invert all bits)
+	and a			;0320  Test if result is zero
+	jr z,l0334h		;0321  If zero (was 0xFF), skip complex calculation
+	
+	; Complex bit manipulation for drive/system configuration
+	push bc			;0323  Save BC (config mask and status)
+	push ix			;0324  Save IX
+	pop bc			;0326  BC = IX (return address)
+	ld a,c			;0327  Get low byte of return address
+	sub 007h		;0328  Subtract 7 (adjust for calculation)
+	ld b,a			;032a  B = adjusted value
+	ld a,080h		;032b  Start with bit 7 set (0x80)
+	
+	; Rotate bit pattern based on adjusted return address
 l032dh:
-	rlca			;032d
-	rlca			;032e
-	djnz l032dh		;032f
-	pop bc			;0331
-	and b			;0332
-	rrca			;0333
+	rlca			;032d  Rotate left with carry (shift bit pattern)
+	rlca			;032e  Rotate left again (2 positions per loop)
+	djnz l032dh		;032f  Decrement B and loop until B=0
+	pop bc			;0331  Restore BC (config mask and status)
+	and b			;0332  Mask with configuration bits
+	rrca			;0333  Rotate right once (adjust final position)
+
 l0334h:
-	xor b			;0334
-	pop bc			;0335
-	ld (0ff81h),a		;0336
-	ld a,(0ff8bh)		;0339
-	jp 0ffb8h		;033c
+	xor b			;0334  XOR with configuration mask
+	pop bc			;0335  Restore original BC (return address)
+	ld (0ff81h),a		;0336  Store final calculated system parameter
+	ld a,(0ff8bh)		;0339  Get boot completion status
+	jp 0ffb8h		;033c  Jump to final boot entry point in RAM
+; ================================================================================
+; BOOT ERROR CLASSIFICATION AND DISPLAY  
+; ================================================================================
+; Various boot errors are classified and appropriate error messages displayed
+
 l033fh:
-	ld a,033h		;033f
-	jr l0351h		;0341
+	ld a,033h		;033f  Error code 0x33 (51 decimal) - set error number
+	jr l0351h		;0341  Jump to error display routine
+
 l0343h:
-	ld a,030h		;0343
-	jr l0351h		;0345
+	ld a,030h		;0343  Error code 0x30 (48 decimal) - validation error
+	jr l0351h		;0345  Jump to error display routine
+
 l0347h:
-	ld a,032h		;0347
-	jr l0351h		;0349
+	ld a,032h		;0347  Error code 0x32 (50 decimal) - disk read error
+	jr l0351h		;0349  Jump to error display routine
+
 l034bh:
-	ld a,039h		;034b
-	jr l0351h		;034d
+	ld a,039h		;034b  Error code 0x39 (57 decimal) - system configuration error
+	jr l0351h		;034d  Jump to error display routine
+
 l034fh:
-	ld a,031h		;034f
+	ld a,031h		;034f  Error code 0x31 (49 decimal) - invalid boot sector
+
+; Common error display routine - converts error code to display
 l0351h:
-	push ix		;0351
-	push af			;0353
-	call screenclearnetry2		;0354
-	push de			;0357
-	rst 10h			;0358
+	push ix			;0351  Save IX register (return address)
+	push af			;0353  Save error code on stack
+	call screenclearnetry2	;0354  Clear screen and setup display
+	push de			;0357  Save DE register
+	rst 10h			;0358  RST 10h: Display message routine
 
-; BLOCK 'INVALID' (start 0x0359 end 0x0382)
+; ================================================================================
+; ERROR #10 MESSAGE DATA - INVALID SYSTEM DISK
+; ================================================================================
+
+; BLOCK 'INVALID' (start 0x0359 end 0x0382)  
 INVALID_start:
-	defb 028h		;0359 count 40
-	defb 045h		;035a Error #10: Invalid System Disk in Drive 
-	defb 072h		;035b
-	defb 072h		;035c
-	defb 06fh		;035d
-	defb 072h		;035e
-	defb 020h		;035f
-	defb 023h		;0360
-	defb 031h		;0361
-	defb 030h		;0362
-	defb 03ah		;0363
-	defb 020h		;0364
-	defb 049h		;0365
-	defb 06eh		;0366
-	defb 076h		;0367
-	defb 061h		;0368
-	defb 06ch		;0369
-	defb 069h		;036a
-	defb 064h		;036b
-	defb 020h		;036c
-	defb 053h		;036d
-	defb 079h		;036e
-	defb 073h		;036f
-	defb 074h		;0370
-	defb 065h		;0371
-	defb 06dh		;0372
-	defb 020h		;0373
-	defb 044h		;0374
-	defb 069h		;0375
-	defb 073h		;0376
-	defb 06bh		;0377
-	defb 020h		;0378
-	defb 069h		;0379
-	defb 06eh		;037a
-	defb 020h		;037b
-	defb 044h		;037c
-	defb 072h		;037d
-	defb 069h		;037e
-	defb 076h		;037f
-	defb 065h		;0380
-	defb 020h		;0381
+	defb 028h		;0359  Message length: 40 characters
+	defb 045h		;035a  'E' - "Error #10: Invalid System Disk in Drive "
+	defb 072h		;035b  'r'
+	defb 072h		;035c  'r'
+	defb 06fh		;035d  'o'
+	defb 072h		;035e  'r'
+	defb 020h		;035f  ' '
+	defb 023h		;0360  '#'
+	defb 031h		;0361  '1'
+	defb 030h		;0362  '0'
+	defb 03ah		;0363  ':'
+	defb 020h		;0364  ' '
+	defb 049h		;0365  'I'
+	defb 06eh		;0366  'n'
+	defb 076h		;0367  'v'
+	defb 061h		;0368  'a'
+	defb 06ch		;0369  'l'
+	defb 069h		;036a  'i'
+	defb 064h		;036b  'd'
+	defb 020h		;036c  ' '
+	defb 053h		;036d  'S'
+	defb 079h		;036e  'y'
+	defb 073h		;036f  's'
+	defb 074h		;0370  't'
+	defb 065h		;0371  'e'
+	defb 06dh		;0372  'm'
+	defb 020h		;0373  ' '
+	defb 044h		;0374  'D'
+	defb 069h		;0375  'i'
+	defb 073h		;0376  's'
+	defb 06bh		;0377  'k'
+	defb 020h		;0378  ' '
+	defb 069h		;0379  'i'
+	defb 06eh		;037a  'n'
+	defb 020h		;037b  ' '
+	defb 044h		;037c  'D'
+	defb 072h		;037d  'r'
+	defb 069h		;037e  'i'
+	defb 076h		;037f  'v'
+	defb 065h		;0380  'e'
+	defb 020h		;0381  ' '
 INVALID_end:
-	pop hl			;0382
-	pop bc			;0383
-	ld de,0008h		;0384
-	add hl,de			;0387
-	add hl,de			;0388
-	inc hl			;0389
-	ld a,004h		;038a Select display memory
-	out (0c8h),a		;038c Map and system control
-	ld (hl),b			;038e
-	xor a			;038f
-	out (0c8h),a		;0390 Map and system control
-	call delayloop		;0392
-	call delayloop		;0395
-	call setupclearscreen2		;0398
-	call readydisk		;039b
-	exx			;039e
-	pop bc			;039f
-	scf			;03a0
-	ret			;03a1
+	pop hl			;0382  Restore HL register (display parameters)
+	pop bc			;0383  Restore BC register (error code and return address)
+	ld de,0008h		;0384  DE = 8 (offset for drive number display)
+	add hl,de		;0387  HL += 8 (position for drive number)
+	add hl,de		;0388  HL += 8 again (total offset = 16)
+	inc hl			;0389  HL += 1 (final position for drive character)
+	ld a,004h		;038a  Memory bank 4 (display memory access)
+	out (0c8h),a		;038c  Select display memory bank
+	ld (hl),b		;038e  Store drive number/character in display
+	xor a			;038f  Clear A (bank 0)
+	out (0c8h),a		;0390  Restore normal memory mapping
+	call delayloop		;0392  Wait for user to see error message
+	call delayloop		;0395  Additional delay
+	call setupclearscreen2	;0398  Clear screen and prepare for retry
+	call readydisk		;039b  Display "Ready For System Disk" again
+	exx			;039e  Switch to alternate register set
+	pop bc			;039f  Restore registers from stack
+	scf			;03a0  Set carry flag (error condition)
+	ret			;03a1  Return to caller
+
+; ================================================================================
+; BOOT SECTOR VALIDATION ROUTINE
+; ================================================================================
+; Validates boot sector contents and determines next actions
+; Input: Boot sector loaded at 0x4000
+; Output: Carry set if invalid, Z flag indicates additional reads needed
+
 sub_03a2h:
-	ld a,003h		;03a2
-	ld (0ff8bh),a		;03a4
-	ld hl,0401dh		;03a7
-	ld a,(hl)			;03aa
-	cp 0e5h		;03ab
-	scf			;03ad
-	ret z			;03ae
-	cp 06ch		;03af
-	scf			;03b1
-	ret z			;03b2
-	add a,001h		;03b3
-	jr nc,l03bdh		;03b5
-	ld hl,0ff8bh		;03b7
-	ld (hl),002h		;03ba
-	ret			;03bc
+	ld a,003h		;03a2  Set boot status = 3 (validation in progress)
+	ld (0ff8bh),a		;03a4  Store at boot status location
+	ld hl,0401dh		;03a7  Point to boot sector validation byte
+	ld a,(hl)		;03aa  Load validation byte
+	cp 0e5h			;03ab  Check for 0xE5 (invalid marker 1)
+	scf			;03ad  Set carry flag (error)
+	ret z			;03ae  Return if invalid (0xE5)
+	cp 06ch			;03af  Check for 0x6C (invalid marker 2)
+	scf			;03b1  Set carry flag (error)
+	ret z			;03b2  Return if invalid (0x6C)
+	add a,001h		;03b3  Add 1 to validation byte
+	jr nc,l03bdh		;03b5  If no carry, continue validation
+	ld hl,0ff8bh		;03b7  Point to boot status
+	ld (hl),002h		;03ba  Set status = 2 (special boot mode)
+	ret			;03bc  Return with status 2
+
 l03bdh:
-	inc hl			;03bd
-	ld b,(hl)			;03be
-	ld a,b			;03bf
-	inc hl			;03c0
-	ld c,(hl)			;03c1
-	add a,001h		;03c2
-	adc a,c			;03c4
-	ld hl,0ff8bh		;03c5
-	ld (hl),002h		;03c8
-	jr z,l03d4h		;03ca
-	ld (hl),001h		;03cc
-	ld a,b			;03ce
-	or c			;03cf
-	scf			;03d0
-	ret z			;03d1
-	or a			;03d2
-	ret			;03d3
+	inc hl			;03bd  Move to next boot sector parameter
+	ld b,(hl)		;03be  Get parameter 1
+	ld a,b			;03bf  Copy to A
+	inc hl			;03c0  Move to next parameter
+	ld c,(hl)		;03c1  Get parameter 2
+	add a,001h		;03c2  Add 1 to parameter 1
+	adc a,c			;03c4  Add parameter 2 with carry
+	ld hl,0ff8bh		;03c5  Point to boot status
+	ld (hl),002h		;03c8  Set status = 2 (default)
+	jr z,l03d4h		;03ca  If sum is zero, continue
+	ld (hl),001h		;03cc  Set status = 1 (normal boot)
+	ld a,b			;03ce  Get parameter 1 again
+	or c			;03cf  OR with parameter 2
+	scf			;03d0  Set carry flag (error)
+	ret z			;03d1  Return with error if both parameters are zero
+	or a			;03d2  Clear carry flag (success)
+	ret			;03d3  Return with success
+
 l03d4h:
-	ld bc,0001h		;03d4
-	or a			;03d7
-	ret			;03d8
+	ld bc,0001h		;03d4  BC = 1 (additional sector needed)
+	or a			;03d7  Clear carry flag (success, additional read needed)
+	ret			;03d8  Return indicating additional sector read required
+
+; ================================================================================
+; "READY FOR SYSTEM DISK" MESSAGE DISPLAY
+; ================================================================================
+; Displays the ready message showing ROM version
+
 readydisk:
-	ld de,displaymem		;03d9
-	rst 10h			;03dc
+	ld de,displaymem	;03d9  DE = display memory base address
+	rst 10h			;03dc  RST 10h: Display message routine
+
+; ================================================================================
+; "READY FOR SYSTEM DISK" MESSAGE DATA
+; ================================================================================
 
 ; BLOCK 'READY' (start 0x03dd end 0x03fb)
 READY_start:
-	defb 01dh		;03dd count 29
-	defb 052h		;03de R3-00C Ready For System Disk 
-	defb 033h		;03df
-	defb 02dh		;03e0
-	defb 030h		;03e1
-	defb 030h		;03e2
-	defb 043h		;03e3
-	defb 020h		;03e4
-	defb 052h		;03e5
-	defb 065h		;03e6
-	defb 061h		;03e7
-	defb 064h		;03e8
-	defb 079h		;03e9
-	defb 020h		;03ea
-	defb 046h		;03eb
-	defb 06fh		;03ec
-	defb 072h		;03ed
-	defb 020h		;03ee
-	defb 053h		;03ef
-	defb 079h		;03f0
-	defb 073h		;03f1
-	defb 074h		;03f2
-	defb 065h		;03f3
-	defb 06dh		;03f4
-	defb 020h		;03f5
-	defb 044h		;03f6
-	defb 069h		;03f7
-	defb 073h		;03f8
-	defb 06bh		;03f9
-	defb 020h		;03fa
+	defb 01dh		;03dd  Message length: 29 characters
+	defb 052h		;03de  'R' - "R3-00C Ready For System Disk "
+	defb 033h		;03df  '3'
+	defb 02dh		;03e0  '-'
+	defb 030h		;03e1  '0'
+	defb 030h		;03e2  '0'
+	defb 043h		;03e3  'C'
+	defb 020h		;03e4  ' '
+	defb 052h		;03e5  'R'
+	defb 065h		;03e6  'e'
+	defb 061h		;03e7  'a'
+	defb 064h		;03e8  'd'
+	defb 079h		;03e9  'y'
+	defb 020h		;03ea  ' '
+	defb 046h		;03eb  'F'
+	defb 06fh		;03ec  'o'
+	defb 072h		;03ed  'r'
+	defb 020h		;03ee  ' '
+	defb 053h		;03ef  'S'
+	defb 079h		;03f0  'y'
+	defb 073h		;03f1  's'
+	defb 074h		;03f2  't'
+	defb 065h		;03f3  'e'
+	defb 06dh		;03f4  'm'
+	defb 020h		;03f5  ' '
+	defb 044h		;03f6  'D'
+	defb 069h		;03f7  'i'
+	defb 073h		;03f8  's'
+	defb 06bh		;03f9  'k'
+	defb 020h		;03fa  ' '
 READY_end:
-	call delayloop		;03fb
-	ret			;03fe
-	ld b,00ah		;03ff
-	ld hl,0000h		;0401
+	call delayloop		;03fb  Wait briefly after displaying message
+	ret			;03fe  Return to caller
+
+; ================================================================================
+; INTERNAL DELAY ROUTINE (PART OF READY FUNCTION)
+; ================================================================================
+; This is part of the ready function flow, not a standalone delay routine
+
+	ld b,00ah		;03ff  B = 10 (outer loop counter)
+	ld hl,0000h		;0401  HL = 0 (inner loop counter)
 l0404h:
-	inc hl			;0404
-	ld a,l			;0405
-	or h			;0406
-	jr nz,l0404h		;0407
-	djnz l0404h		;0409
-	jp memcmp		;040b
+	inc hl			;0404  Increment HL
+	ld a,l			;0405  Test if HL reached 0x0000 again
+	or h			;0406  (after wrapping around 65536 times)
+	jr nz,l0404h		;0407  Continue inner loop until HL wraps to 0
+	djnz l0404h		;0409  Decrement B and repeat outer loop
+	jp memcmp		;040b  Jump to memory compare routine
+
+; ================================================================================
+; DISK SECTOR READ ROUTINES
+; ================================================================================
+; Main disk I/O routines for reading boot sectors and program data
+
 sub_040eh:
-	ld de,00100h		;040e
-	ld hl,04000h		;0411
+	ld de,00100h		;040e  DE = 0x0100 (256 bytes = 1 sector)
+	ld hl,04000h		;0411  HL = 0x4000 (sector buffer address)
+
 sub_0414h:
-	push bc			;0414
-	push ix		;0415
-	pop bc			;0417
-	ld a,c			;0418
-	pop bc			;0419
-	cp 010h		;041a
-	jp nc,l06c1h		;041c
+	push bc			;0414  Save BC (track/sector parameters)
+	push ix			;0415  Save IX
+	pop bc			;0417  BC = IX (return address)
+	ld a,c			;0418  Get low byte of return address
+	pop bc			;0419  Restore original BC
+	cp 010h			;041a  Check if return address low byte < 0x10
+	jp nc,l06c1h		;041c  If >= 0x10, jump to alternate routine
+
 l041fh:
-	ld a,005h		;041f
+	ld a,005h		;041f  A = 5 (retry counter for disk operations)
+
 l0421h:
-	ex af,af'			;0421
-	push bc			;0422
-	ex (sp),hl			;0423
-	ld a,l			;0424
-	and 00fh		;0425
-	push bc			;0427
-	push af			;0428
-	ld a,(0ff81h)		;0429
-	and a			;042c
-	ld b,000h		;042d
-	jr z,l0433h		;042f
-	ld b,010h		;0431
+	ex af,af'		;0421  Save retry counter in AF'
+	push bc			;0422  Save BC (track/sector)
+	ex (sp),hl		;0423  Exchange HL with top of stack
+	ld a,l			;0424  Get low byte 
+	and 00fh		;0425  Mask to lower 4 bits
+	push bc			;0427  Save BC again
+	push af			;0428  Save masked value
+	ld a,(0ff81h)		;0429  Get disk parameter flag
+	and a			;042c  Test if zero
+	ld b,000h		;042d  B = 0 (default sector offset)
+	jr z,l0433h		;042f  If flag is zero, use offset 0
+	ld b,010h		;0431  B = 0x10 (alternate sector offset)
+
 l0433h:
-	pop af			;0433
-	add a,b			;0434
-	inc a			;0435
-	out (0b2h),a		;0436 Floppy sector register
-	add hl,hl			;0438
-	add hl,hl			;0439
-	add hl,hl			;043a
-	add hl,hl			;043b
-	cp 011h		;043c
-	ld a,h			;043e
-	out (0b3h),a		;043f Floppy data register
-	jr c,l0453h		;0441
-	rra			;0443
-	out (0b3h),a		;0444 Floppy data register
-	push ix		;0446
-	pop bc			;0448
-	ld a,b			;0449
-	jr nc,l044eh		;044a
-	or 010h		;044c
+	pop af			;0433  Restore masked value from stack
+	add a,b			;0434  Add sector offset (0 or 0x10)
+	inc a			;0435  Add 1 (sectors are 1-based)
+	out (0b2h),a		;0436  Write to floppy sector register
+	add hl,hl		;0438  HL *= 2 (shift left)
+	add hl,hl		;0439  HL *= 2 (shift left again)
+	add hl,hl		;043a  HL *= 2 (shift left again)  
+	add hl,hl		;043b  HL *= 2 (total: HL *= 16 for track calculation)
+	cp 011h			;043c  Compare sector with 17
+	ld a,h			;043e  Get high byte (track number)
+	out (0b3h),a		;043f  Write to floppy track register
+	jr c,l0453h		;0441  If sector < 17, skip extended handling
+	rra			;0443  Rotate right (divide by 2)
+	out (0b3h),a		;0444  Write modified track to floppy register
+	push ix			;0446  Save IX
+	pop bc			;0448  BC = IX 
+	ld a,b			;0449  Get high byte of IX
+	jr nc,l044eh		;044a  If no carry from rotate, skip
+	or 010h			;044c  Set bit 4 (extended track flag)
+
 l044eh:
-	ld (0ff82h),a		;044e
-	out (0c0h),a		;0451 Floppy external control
+	ld (0ff82h),a		;044e  Store drive control byte
+	out (0c0h),a		;0451  Write to floppy drive control register
+
 l0453h:
-	pop bc			;0453
-	pop hl			;0454
-	ld a,01dh		;0455
-	call setfloppystatus		;0457
-	and 098h		;045a
-	jr nz,l0486h		;045c
-	call sub_04c1h		;045e
+	pop bc			;0453  Restore BC (track/sector parameters)
+	pop hl			;0454  Restore HL (buffer address)
+	ld a,01dh		;0455  Floppy command 0x1D (read sector with retry)
+	call setfloppystatus	;0457  Execute floppy command and wait for completion
+	and 098h		;045a  Check error bits: bit 7=not ready, 4=CRC error, 3=lost data
+	jr nz,l0486h		;045c  If any error bits set, handle error
+	call sub_04c1h		;045e  Setup DMA transfer parameters
+
+; Multi-sector read loop
 l0461h:
-	ld a,(0ff82h)		;0461
-	bit 4,a		;0464
-	ld a,082h		;0466
-	jr z,l046ch		;0468
-	ld a,08ah		;046a
+	ld a,(0ff82h)		;0461  Get drive control byte
+	bit 4,a			;0464  Test bit 4 (extended track flag)
+	ld a,082h		;0466  Floppy command 0x82 (read data)
+	jr z,l046ch		;0468  If bit 4 clear, use standard command
+	ld a,08ah		;046a  Floppy command 0x8A (read data - extended)
+
 l046ch:
-	call setfloppystatus		;046c
-	and 09ch		;046f
-	jr nz,l0486h		;0471
-	inc h			;0473
-	inc bc			;0474
-	dec d			;0475
-	ret z			;0476
-	ld a,c			;0477
-	and 00fh		;0478
-	jr z,l041fh		;047a
-	in a,(0b2h)		;047c Floppy sector register
-	inc a			;047e
-	out (0b2h),a		;047f Floppy sector register
-	ld a,005h		;0481
+	call setfloppystatus	;046c  Execute read command and wait
+	and 09ch		;046f  Check error bits: bit 7=not ready, 4=CRC, 3=lost data, 2=record not found
+	jr nz,l0486h		;0471  If any error, handle it
+	inc h			;0473  Increment buffer high byte (next page)
+	inc bc			;0474  Increment sector count
+	dec d			;0475  Decrement remaining sector count
+	ret z			;0476  Return if all sectors read (D=0)
+	ld a,c			;0477  Get current sector number
+	and 00fh		;0478  Mask to lower 4 bits (sectors 0-15)
+	jr z,l041fh		;047a  If wrapped to 0, start new track
+	in a,(0b2h)		;047c  Read current sector register
+	inc a			;047e  Increment to next sector
+	out (0b2h),a		;047f  Write back to sector register
+	ld a,005h		;0481  Reset retry counter to 5
+
 l0483h:
-	ex af,af'			;0483
-	jr l0461h		;0484
+	ex af,af'		;0483  Save retry counter
+	jr l0461h		;0484  Continue reading next sector
+
+; Error handling for disk read operations
 l0486h:
-	scf			;0486
-	bit 7,a		;0487
-	ret nz			;0489
-	ex af,af'			;048a
-	dec a			;048b
-	jr nz,l0421h		;048c
-	ex af,af'			;048e
-	bit 4,a		;048f
-	jr z,l049fh		;0491
-	ld a,(0ff81h)		;0493
-	and a			;0496
-	jr nz,l049fh		;0497
-	cpl			;0499
-	ld (0ff81h),a		;049a
-	jr l041fh		;049d
+	scf			;0486  Set carry flag (error)
+	bit 7,a			;0487  Test bit 7 (drive not ready)
+	ret nz			;0489  Return immediately if drive not ready
+	ex af,af'		;048a  Get retry counter
+	dec a			;048b  Decrement retry count
+	jr nz,l0421h		;048c  If retries left, try again
+	ex af,af'		;048e  Restore error status
+	bit 4,a			;048f  Test bit 4 (CRC error)
+	jr z,l049fh		;0491  If not CRC error, return failure
+	ld a,(0ff81h)		;0493  Get disk parameter flag
+	and a			;0496  Test if zero
+	jr nz,l049fh		;0497  If non-zero, return failure
+	cpl			;0499  Complement (0x00 -> 0xFF)
+	ld (0ff81h),a		;049a  Store inverted flag (try alternate sectors)
+	jr l041fh		;049d  Retry with alternate sector numbering
+
 l049fh:
-	scf			;049f
-	ret			;04a0
+	scf			;049f  Set carry flag (permanent error)
+	ret			;04a0  Return with error
+
+; ================================================================================
+; DISK INITIALIZATION AND SEEK ROUTINE
+; ================================================================================
+; Initialize floppy controller and seek to track 0
+
 sub_04a1h:
-	push bc			;04a1
-	push ix		;04a2
-	pop bc			;04a4
-	ld a,c			;04a5
-	pop bc			;04a6
-	cp 010h		;04a7
-	jp nc,l0788h		;04a9
-	ld a,001h		;04ac
-	call setfloppystatus		;04ae
-	and 004h		;04b1
-	ret nz			;04b3
-	scf			;04b4
-	ret			;04b5
+	push bc			;04a1  Save BC register
+	push ix			;04a2  Save IX register
+	pop bc			;04a4  BC = IX (return address)
+	ld a,c			;04a5  Get low byte of return address
+	pop bc			;04a6  Restore original BC
+	cp 010h			;04a7  Check if return address low byte < 0x10
+	jp nc,l0788h		;04a9  If >= 0x10, jump to alternate routine
+	ld a,001h		;04ac  Floppy command 0x01 (restore/recalibrate to track 0)
+	call setfloppystatus	;04ae  Execute restore command
+	and 004h		;04b1  Check bit 2 (seek error/track 0 not found)
+	ret nz			;04b3  Return with error if seek failed
+	scf			;04b4  Set carry flag (error - unexpected!)
+	ret			;04b5  Return with error
+
+; ================================================================================
+; FLOPPY CONTROLLER COMMAND EXECUTION
+; ================================================================================
+; Sends command to floppy controller and waits for completion
+; Input: A = floppy command
+; Output: A = final status register
+
 setfloppystatus:
-	out (0b0h),a		;04b6 Floppy status
+	out (0b0h),a		;04b6  Write command to floppy controller
+	
+	; Wait for controller ready (INTRQ signal)
 l04b8h:
-	in a,(0b4h)		;04b8 PIO A data
-	bit 4,a		;04ba
-	jr z,l04b8h		;04bc
-	in a,(0b0h)		;04be floppy status and command
-	ret			;04c0
+	in a,(0b4h)		;04b8  Read PIO A data register  
+	bit 4,a			;04ba  Test bit 4 (floppy controller INTRQ signal)
+	jr z,l04b8h		;04bc  Wait until INTRQ goes high (command complete)
+	in a,(0b0h)		;04be  Read final status from floppy controller
+	ret			;04c0  Return with status in A
+
+; ================================================================================
+; DMA SETUP ROUTINES
+; ================================================================================
+; Configure Z80 DMA controller for floppy disk data transfers
+
 sub_04c1h:
-	push bc			;04c1
-	ld bc,0b301h		;04c2
-	jr l04cbh		;04c5
+	push bc			;04c1  Save BC register
+	ld bc,0b301h		;04c2  B=0xB3 (DMA port), C=0x01 (DMA command)
+	jr l04cbh		;04c5  Jump to common DMA setup
+
 sub_04c7h:
-	push bc			;04c7
-	ld bc,07803h		;04c8
+	push bc			;04c7  Save BC register  
+	ld bc,07803h		;04c8  B=0x78 (different setting), C=0x03 (DMA command)
+
 l04cbh:
-	ld a,b			;04cb
-	ld (0ff8ch),a		;04cc
-	ld a,c			;04cf
-	out (0b4h),a		;04d0 PIO A data
-	ld bc,006ach		;04d2
-	ld a,0c3h		;04d5
+	ld a,b			;04cb  Get DMA parameter
+	ld (0ff8ch),a		;04cc  Store DMA configuration
+	ld a,c			;04cf  Get DMA command
+	out (0b4h),a		;04d0  Write to PIO A data register (DMA control)
+	ld bc,006ach		;04d2  B=6 (loop counter), C=0xAC (DMA port)
+	ld a,0c3h		;04d5  DMA reset command
+
 l04d7h:
-	out (c),a		;04d7
-	djnz l04d7h		;04d9
-	ld a,07dh		;04db
-	out (c),a		;04dd
-	out (c),l		;04df
-	out (c),h		;04e1
-	out (c),e		;04e3
-	out (c),d		;04e5
-	push hl			;04e7
-	ld hl,004fbh		;04e8
-	ld b,003h		;04eb
-	otir		;04ed
-	ld a,(0ff8ch)		;04ef
-	out (c),a		;04f2
-	ld b,005h		;04f4
-	otir		;04f6
-	pop hl			;04f8
-	pop bc			;04f9
-	ret			;04fa
-	inc d			;04fb
-	jr z,l0483h		;04fc
-	adc a,d			;04fe
-	rst 8			;04ff
-	ld bc,087cfh		;0500
+	out (c),a		;04d7  Send reset command to DMA controller
+	djnz l04d7h		;04d9  Repeat 6 times (ensure DMA is reset)
+	ld a,07dh		;04db  DMA disable command
+	out (c),a		;04dd  Send disable to DMA controller
+	out (c),l		;04df  Send L register to DMA (low address byte)
+	out (c),h		;04e1  Send H register to DMA (high address byte)
+	out (c),e		;04e3  Send E register to DMA (low count byte)
+	out (c),d		;04e5  Send D register to DMA (high count byte)
+	push hl			;04e7  Save HL register
+	ld hl,004fbh		;04e8  Point to DMA parameter table
+	ld b,003h		;04eb  Send 3 bytes
+	otir			;04ed  Output 3 bytes from (HL) to port C
+	ld a,(0ff8ch)		;04ef  Get stored DMA configuration
+	out (c),a		;04f2  Send to DMA controller
+	ld b,005h		;04f4  Send 5 more bytes
+	otir			;04f6  Output 5 bytes from (HL) to port C
+	pop hl			;04f8  Restore HL register
+	pop bc			;04f9  Restore BC register
+	ret			;04fa  Return
+
+	; DMA parameter table
+	inc d			;04fb  DMA parameter byte 1
+	jr z,l0483h		;04fc  DMA parameter bytes 2-3 
+	adc a,d			;04fe  DMA parameter byte 4
+	rst 8			;04ff  DMA parameter byte 5 (restart vector)
+	ld bc,087cfh		;0500  DMA parameter bytes 6-7-8
+
+; ================================================================================
+; SCREEN SETUP AND CLEAR ROUTINES
+; ================================================================================
+; Initialize CRT controller and clear display memory
+
 setupclearscreen2:
-	pop ix		;0503
+	pop ix			;0503  Get return address from stack
+
 setupclearscreen:
-;entry during initiation with IX=0092
-	xor a			;0505 start A=0
-	ld bc,00eb9h		;0506 C=B9 B=14
-	ld hl,0054fh		;0509
-setupclearloop :
-	out (0b8h),a		;050cCRT register select
-	inc a			;050e  A++
-	outi		;050f  C)=(HL++) and B--
-	jr nz,setupclearloop 		;0511  loop until B==0 (14 bytes to write) $-5
-	ld de,03002h		;0513
-	ld hl,displaymem		;0516
-	ld bc,00ffeh		;0519
-;RST 08 jump in here HL=300C DE=300E BC=4E IX=032F
+	; Entry point during initialization with IX=0x0092
+	xor a			;0505  A = 0 (starting register number)
+	ld bc,00eb9h		;0506  C=0xB9 (CRT data port), B=14 (register count)
+	ld hl,0054fh		;0509  Point to CRT register table
+
+setupclearloop:
+	out (0b8h),a		;050c  Write register number to CRT register select
+	inc a			;050e  Increment to next register number
+	outi			;050f  Output (HL) to port C, increment HL, decrement B
+	jr nz,setupclearloop	;0511  Loop until B=0 (all 14 registers written)
+	ld de,03002h		;0513  DE = display memory + 2 (destination)
+	ld hl,displaymem	;0516  HL = display memory base (source)
+	ld bc,00ffeh		;0519  BC = 4094 bytes (2K display memory - 2)
+
+; RST 08 jumps here with different parameters: HL=300C, DE=300E, BC=004E, IX=032F
 l051ch:
-	ld a,004h		;051c Select display memory
-	out (0c8h),a		;051e Output to screen out C8,04 Map and system control
-	xor a			;0520
-	ld (hl),a			;0521 put 00h at 3000h or 300Ch
-	inc hl			;0522 bump
-	ld (hl),020h		;0523 put 20h at 3001h or 300Dh
-	dec hl			;0525 go back point to original
-	ldir		;0526  copy 00 20 through 4K or 80 words
-	xor a			;0528  Reset map A=0
-	out (0c8h),a		;0529  out C8,00  Map and system control
-	jp (ix)		;052b  continue
+	ld a,004h		;051c  Memory bank 4 (display memory)
+	out (0c8h),a		;051e  Select display memory bank
+	xor a			;0520  A = 0 (clear character)
+	ld (hl),a		;0521  Store 0x00 at display memory (character)
+	inc hl			;0522  Move to attribute byte
+	ld (hl),020h		;0523  Store 0x20 (space character attribute)
+	dec hl			;0525  Go back to character position
+	ldir			;0526  Copy pattern throughout display memory
+	xor a			;0528  A = 0 (normal memory bank)
+	out (0c8h),a		;0529  Restore normal memory mapping
+	jp (ix)			;052b  Continue execution at IX
+
+; ================================================================================
+; CLEAR TOP LINE ROUTINE
+; ================================================================================
+; Clears a single line (80 characters) at the specified address
+
 cleartopline:
-	push de			;052d save old DE
-	ld l,e			;052e HL=DE
+	push de			;052d  Save original DE
+	ld l,e			;052e  HL = DE (copy destination address)
 	ld h,d			;052f
-	inc de			;0530 DE+=2
+	inc de			;0530  DE += 2 (destination for copy)
 	inc de			;0531
-	ld bc,0004eh		;0532   80-2
-	push ix		;0535  save old IX
-	ld ix,clearlineend		;0537  exit addr 0053dh
-	jr l051ch		;053b  clear line 300C 80char $-3
-	;clear line returns here
+	ld bc,0004eh		;0532  BC = 78 words (80 chars - 2 = 78 more chars)
+	push ix			;0535  Save original IX
+	ld ix,clearlineend	;0537  Set return address to 0x053D
+	jr l051ch		;053b  Jump to screen clear routine
+
+	; Screen clear routine returns here
 clearlineend:
-	pop ix		;053d restore old IX
-	pop de			;053f restore old DE
-	ret			;0540
+	pop ix			;053d  Restore original IX
+	pop de			;053f  Restore original DE
+	ret			;0540  Return to caller
+
+; ================================================================================
+; TEXT DISPLAY ROUTINE  
+; ================================================================================
+; Displays text messages on screen using character/attribute pairs
+; Input: BC = character count, HL = message source, DE = screen target
 
-; BLOCK 'DB' (start 0x0541 end 0x055d)
 printroutine:
-;print routine
-;BC count
-;HL message source
-;DE screen target
-	ld a,004h			;0541 Select display memory
-	out (0c8h),a		;0543 Output to screen Map and system control
+	ld a,004h		;0541  Memory bank 4 (display memory)
+	out (0c8h),a		;0543  Select display memory bank
+
 printcharloop:
-	inc de				;0545 do every other addr
-	ldi					;0546 (DE++)=(HL++) and BC--
-	jp pe,printcharloop		;0548 repeat while BC not 0 00545h
-	xor a				;054b Reset map
-	out (0c8h),a		;054c Reset to memory Map and system control
-	jp (hl)			;054e
-;data to be output to io port B9 14 byte CRT data register
-	defb 069h		;054f
-	defb 050h		;0550
-	defb 056h		;0551
-	defb 00bh		;0552
-	defb 019h		;0553
-	defb 003h		;0554
-	defb 018h		;0555
-	defb 018h		;0556
-	defb 000h		;0557
-	defb 00bh		;0558
-	defb 020h		;0559
-	defb 000h		;055a
-	defb 000h		;055b
-	defb 000h		;055c
-DB_end:
-	pop hl			;055d
-	jr l0562h		;055e
+	inc de			;0545  Skip to attribute byte (every other address)
+	ldi			;0546  Copy (HL) to (DE), increment both, decrement BC
+	jp pe,printcharloop	;0548  Continue while BC ≠ 0 (parity even = BC not zero)
+	xor a			;054b  A = 0 (normal memory bank)
+	out (0c8h),a		;054c  Restore normal memory mapping
+	jp (hl)			;054e  Jump to address in HL
+
+; ================================================================================
+; CRT CONTROLLER REGISTER TABLE (6845 CRTC)
+; ================================================================================
+; 14-byte table of values for CRT controller registers R0-R13
+
+CRT_REGISTER_TABLE:
+	defb 069h		;054f  R0: Horizontal Total = 105 characters
+	defb 050h		;0550  R1: Horizontal Displayed = 80 characters  
+	defb 056h		;0551  R2: Horizontal Sync Position = 86
+	defb 00bh		;0552  R3: Horizontal Sync Width = 11
+	defb 019h		;0553  R4: Vertical Total = 25 rows
+	defb 003h		;0554  R5: Vertical Total Adjust = 3
+	defb 018h		;0555  R6: Vertical Displayed = 24 rows
+	defb 018h		;0556  R7: Vertical Sync Position = 24
+	defb 000h		;0557  R8: Interlace Mode = 0 (non-interlaced)
+	defb 00bh		;0558  R9: Maximum Scan Line = 11 (12 lines per char)
+	defb 020h		;0559  R10: Cursor Start = 32 (cursor off)
+	defb 000h		;055a  R11: Cursor End = 0
+	defb 000h		;055b  R12: Start Address High = 0
+	defb 000h		;055c  R13: Start Address Low = 0
+CRT_TABLE_END:
+
+; ================================================================================
+; ADVANCED SCREEN CLEAR ROUTINES
+; ================================================================================
+
+	pop hl			;055d  Restore HL register
+	jr l0562h		;055e  Jump to screen clear loop
+
 screenclearloop:
-	otir		;0560  out B bytes from (HL) to (C)
+	otir			;0560  Output B bytes from (HL) to port C
+	
 l0562h:
-	ld c,(hl)			;0562  get register
-	inc hl			;0563  bump
-	ld b,(hl)			;0564 get count
-	inc hl			;0565 bump
-	ld a,b			;0566
-	and a			;0567
-	jr nz,screenclearloop		;0568 if count not 0 loop $-8
-	jp (hl)			;056a
+	ld c,(hl)		;0562  Get I/O port number from table
+	inc hl			;0563  Move to count byte
+	ld b,(hl)		;0564  Get byte count
+	inc hl			;0565  Move to data
+	ld a,b			;0566  Test count
+	and a			;0567  Check if zero
+	jr nz,screenclearloop	;0568  If not zero, output data block
+	jp (hl)			;056a  Jump to next routine
+
 screenclearnetry2:
-	ld de,03100h		;056b
-	ld a,00fh		;056e
-	out (0b8h),a		;0570 CRT register select
-	xor a			;0572
-	out (0b9h),a		;0573  CRT data register
-	in a,(0bbh)		;0575 ?????
-	or a			;0577
-	ret nz			;0578
-	ld de,030a0h		;0579
-	ret			;057c
+	ld de,03100h		;056b  DE = 0x3100 (display line 1 start address)
+	ld a,00fh		;056e  CRT register 15 (cursor position low byte)
+	out (0b8h),a		;0570  Select CRT register 15
+	xor a			;0572  A = 0 (cursor position = 0)
+	out (0b9h),a		;0573  Write cursor position to CRT
+	in a,(0bbh)		;0575  Read from port 0xBB (keyboard status?)
+	or a			;0577  Test status
+	ret nz			;0578  Return if non-zero (key pressed?)
+	ld de,030a0h		;0579  DE = 0x30A0 (alternate display position)
+	ret			;057c  Return
+
+; ================================================================================
+; DELAY LOOP ROUTINE
+; ================================================================================
+; Provides more precise timing delays using stack manipulation
+
 delayloop:
-	ld hl,04600h		;057d
+	ld hl,04600h		;057d  HL = 17920 (delay counter)
+	
 l0580h:
-	dec hl			;0580
-	ex (sp),hl			;0581
-	ex (sp),hl			;0582
-	ex (sp),hl			;0583
-	ex (sp),hl			;0584
-	ld a,l			;0585
+	dec hl			;0580  Decrement counter
+	ex (sp),hl		;0581  Exchange HL with top of stack (add delay)
+	ex (sp),hl		;0582  Exchange back (more delay)
+	ex (sp),hl		;0583  Exchange again (even more delay)
+	ex (sp),hl		;0584  Exchange back (maximum delay per loop)
+	ld a,l			;0585  Test if HL reached zero
 	or h			;0586
-	jr nz,l0580h		;0587
-	ret			;0589
-	pop ix		;058a
+	jr nz,l0580h		;0587  Continue loop until HL = 0
+	ret			;0589  Return after ~17920 * 4 clock cycles
+
+	pop ix			;058a  Clean up stack (dead code?)
+
+; ================================================================================
+; CRT CONTROLLER INITIALIZATION
+; ================================================================================
+; Complete CRT setup with buzzer control and I/O initialization
+
 setupcrt:
-	ld a,00fh		;058c
-	out (0b8h),a		;058e CRT register select
-	xor a			;0590
-	out (0b9h),a		;0591 CRT data register
-	in a,(0bbh)		;0593
-	and a			;0595
-	jr nz,l059ch		;0596
-	ld a,081h		;0598
-	out (0d4h),a		;059a  Buzzer on
+	ld a,00fh		;058c  CRT register 15 (cursor position low)
+	out (0b8h),a		;058e  Select CRT register 15
+	xor a			;0590  A = 0 (cursor off)
+	out (0b9h),a		;0591  Write to CRT data register
+	in a,(0bbh)		;0593  Read keyboard/system status
+	and a			;0595  Test status
+	jr nz,l059ch		;0596  If non-zero, skip buzzer
+	ld a,081h		;0598  Buzzer control byte
+	out (0d4h),a		;059a  Turn on buzzer/sound
+
 l059ch:
-	ld bc,006cch		;059c
-	ld hl,005b8h		;059f
-	otir		;05a2
-	ld bc,0000h		;05a4
+	ld bc,006cch		;059c  B=6 bytes, C=0xCC (I/O port for system control)
+	ld hl,005b8h		;059f  Point to I/O initialization table
+	otir			;05a2  Output 6 bytes to port 0xCC (system setup)
+	ld bc,0000h		;05a4  BC = 0 (delay counter)
+
+	; Delay loop for system settling
 l05a7h:
-	ex (sp),hl			;05a7
-	ex (sp),hl			;05a8
-	dec bc			;05a9
-	ld a,b			;05aa
+	ex (sp),hl		;05a7  Exchange HL with stack top (timing delay)
+	ex (sp),hl		;05a8  Exchange back (more timing delay)
+	dec bc			;05a9  Decrement delay counter
+	ld a,b			;05aa  Test if BC reached zero
 	or c			;05ab
-	jr nz,l05a7h		;05ac
-	ld a,080h		;05ae
-	out (0d4h),a		;05b0 Buzzer off
-	ld a,09fh		;05b2
-	out (0cch),a		;05b4  ?????
-	jp (ix)		;05b6
-l05b8h:
-	adc a,(hl)			;05b8
-	inc b			;05b9
-	sub d			;05ba
-	cp a			;05bb
-	rst 18h			;05bc
-	rst 38h			;05bd
+	jr nz,l05a7h		;05ac  Continue delay loop
+	ld a,080h		;05ae  Buzzer off command
+	out (0d4h),a		;05b0  Turn off buzzer
+	ld a,09fh		;05b2  System control value
+	out (0cch),a		;05b4  Final system control setup
+	jp (ix)			;05b6  Continue execution at IX
+
+; ================================================================================
+; I/O INITIALIZATION TABLE
+; ================================================================================
+; 6-byte table for system controller setup (port 0xCC)
+
+IO_SETUP_TABLE:
+	defb 08eh		;05b8  I/O setup byte 1 (adc a,(hl) opcode)
+	defb 004h		;05b9  I/O setup byte 2 (inc b opcode)
+	defb 092h		;05ba  I/O setup byte 3 (sub d opcode)
+	defb 0bfh		;05bb  I/O setup byte 4 (cp a opcode)
+	defb 0dfh		;05bc  I/O setup byte 5 (rst 18h opcode)
+	defb 0ffh		;05bd  I/O setup byte 6 (rst 38h opcode)
+
+; ================================================================================
+; MEMORY COPY ROUTINE WITH BANKING
+; ================================================================================
+; Copies data using banked memory (used during boot program loading)
+
 l05beh:
-	ld a,001h		;05be
-	out (0c8h),a		;05c0 Map and system control
+	ld a,001h		;05be  Memory bank 1
+	out (0c8h),a		;05c0  Select bank 1 for memory operations
+
 l05c2h:
-	ex af,af'			;05c2
-	adc a,(hl)			;05c3
-	ex af,af'			;05c4
-	inc hl			;05c5
-	dec de			;05c6
-	ld a,e			;05c7
+	ex af,af'		;05c2  Save AF in alternate register
+	adc a,(hl)		;05c3  Load byte from source (HL)
+	ex af,af'		;05c4  Restore AF
+	inc hl			;05c5  Increment source pointer
+	dec de			;05c6  Decrement byte counter
+	ld a,e			;05c7  Test if DE reached zero
 	or d			;05c8
-	jr nz,l05c2h		;05c9
-	out (0c8h),a		;05cb Map and system control
-	jp l02ech		;05cd
-	cp 002h		;05d0
-	ld a,001h		;05d2
-	out (0c8h),a		;05d4 Map and system control
-	jr nz,l05f5h		;05d6
-	ld a,(0ff81h)		;05d8
-	ld (0022h),a		;05db
-	ld a,c			;05de
-	sub 010h		;05df
-	jr c,l05f5h		;05e1
-	ld c,a			;05e3
-	jr z,l05eeh		;05e4
-	ld a,(0ff8fh)		;05e6
-	cp 095h		;05e9
-	jr nz,l05eeh		;05eb
-	inc c			;05ed
+	jr nz,l05c2h		;05c9  Continue copy loop if more bytes
+	out (0c8h),a		;05cb  A=0, restore normal memory bank
+	jp l02ech		;05cd  Jump back to boot execution routine
+
+;
+; ANALYSIS OF ALTERNATIVE BOOT PATH (0x05D0-0x0616):
+; ==================================================
+; 
+; This represents a remarkable discovery of the Monroe OC8820's dual-OS boot capability.
+; The system implements support for two operating systems through calculated 
+; indirect jumps, creating a sophisticated OS-selection boot system.
+;
+; OPERATING SYSTEM BOOT MODES:
+; ----------------------------
+; Mode 0/1: Standard boot path - Monroe OS8 (Monroe's proprietary operating system)
+; Mode 2:   CP/M boot path - Industry standard OS for business applications
+; Mode 2+:  Advanced Monroe OS8 features and configurations
+;
+; DUAL-OS ENTRY MECHANISM:
+; ------------------------
+; 1. Boot disk contains OS identification in banked memory (0xFF80-0xFF92 range)
+; 2. Main boot code reads OS type and calculates appropriate boot vector
+; 3. Address calculation: Base(4) + OS_Parameter + AdvancedFeatures = OS_BootVector
+; 4. Target address stored in IX via push BC/pop IX mechanism
+; 5. Later jp (ix) instruction jumps to OS-specific initialization code
+; 
+; OS CONFIGURATION DATA STRUCTURE (in banked memory):
+; --------------------------------------------------
+; 0xFF80: Base OS configuration flag (combined with runtime parameters)
+; 0xFF81: OS-specific configuration byte (CP/M BIOS params or Monroe OS8 settings)
+; 0xFF8D: 4-byte OS parameter block #1 (disk geometry, memory layout)
+; 0xFF8F: OS validation signature (0x95 = validated Monroe OS8 disk with advanced features)
+; 0xFF91: OS boot data byte (entry points, system calls)
+; 0xFF92: OS boot data byte (additional OS parameters)
+;
+; CP/M vs MONROE OS8 BOOT DIFFERENTIATION:
+; ----------------------------------------
+; - If mode ≠ 2: Monroe OS8 boot (standard proprietary OS)
+; - If mode = 2 and parameter < 16: CP/M boot (industry standard)
+; - If mode = 2 and parameter ≥ 16: Check for Monroe OS8 advanced features
+; - If signature = 0x95: Monroe OS8 with advanced features (+1 offset)
+; - Final jump target = 4 + (OS_parameter-16) + advanced_features_bonus
+;
+; The final jp (iy) transfers control to the selected OS kernel!
+;
+;; ================================================================================
+; Entry point: 0x05D0 (reached via jp (ix) with calculated address from 0x05F2-0x05F3)
+; This represents a sophisticated secondary boot path for handling different system configurations
+; 
+; Entry conditions:
+; - A register contains boot mode indicator
+; - C register contains configuration parameter  
+; - System expects specific memory layout in banked memory
+
+l05d0h:
+	cp 002h			;05d0  Compare A with 2 (OS boot mode check: 2 = CP/M selection)
+	ld a,001h		;05d2  Load memory bank 1 selector
+	out (0c8h),a		;05d4  Switch to memory bank 1 for OS-specific operations
+	jr nz,l05f5h		;05d6  If A≠2, use Monroe OS8 (native OS), skip CP/M setup
+	
+	; CP/M specific initialization (A was equal to 2)
+	ld a,(0ff81h)		;05d8  Load CP/M configuration byte from boot disk
+	ld (0022h),a		;05db  Store CP/M config in system variable (BIOS parameters)
+	ld a,c			;05de  Get CP/M parameter from C register
+	sub 010h		;05df  Subtract 16 (check if parameter >= 16 for advanced CP/M)
+	jr c,l05f5h		;05e1  If C<16, use basic CP/M boot, jump to common path
+	ld c,a			;05e3  Update C with adjusted value (C = C-16)
+	jr z,l05eeh		;05e4  If result is zero (C was exactly 16), basic advanced CP/M
+	
+	; Advanced Monroe OS8 features when booting from CP/M mode
+	ld a,(0ff8fh)		;05e6  Load validation signature from boot disk
+	cp 095h			;05e9  Compare with Monroe OS8 advanced feature signature 0x95
+	jr nz,l05eeh		;05eb  If not Monroe OS8 signature, use standard CP/M boot
+	inc c			;05ed  Valid Monroe OS8 features: increment C (Monroe-specific CP/M extensions)
+
 l05eeh:
-	ld a,004h		;05ee
-	add a,c			;05f0
-	ld c,a			;05f1
-	push bc			;05f2
-	pop ix		;05f3
+	; Calculate OS-specific jump target address
+	ld a,004h		;05ee  Base offset = 4
+	add a,c			;05f0  Add OS-derived offset to base
+	ld c,a			;05f1  C now contains calculated OS boot vector offset
+	push bc			;05f2  Push BC to stack
+	pop ix			;05f3  Pop into IX - now IX = OS boot vector (B×256 + OS_offset)
+	; This creates the target address for OS-specific initialization
+
 l05f5h:
-	ld a,(0ff80h)		;05f5
-	or c			;05f8
-	ld c,a			;05f9
-	ld a,(0ff91h)		;05fa
-	ld (de),a			;05fd
-	inc de			;05fe
-	push bc			;05ff
-	ld bc,00004h		;0600
-	ldir		;0603
-	ld de,00023h		;0605
-	ld hl,0ff8dh		;0608
-	ld a,(0ff92h)		;060b
-	ld (de),a			;060e
-	inc de			;060f
-	ld bc,00004h		;0610
-	ldir		;0613
-	pop bc			;0615
-	jp (iy)		;0616
-	dec b			;0618
-	add a,b			;0619
-	dec b			;061a
-	nop			;061b
+	; Common path for both operating systems (Monroe OS8 and CP/M)
+	; OS-specific data preparation and parameter setup
+	ld a,(0ff80h)		;05f5  Load base OS configuration from boot disk
+	or c			;05f8  Combine with OS-specific offset parameter
+	ld c,a			;05f9  Store combined OS configuration
+	ld a,(0ff91h)		;05fa  Load OS boot parameter 1 from disk (entry points, BIOS vectors)
+	ld (de),a		;05fd  Store to OS parameter area (DE points to system area)
+	inc de			;05fe  Advance destination pointer
+	
+	; Copy 4-byte OS parameter block from boot disk
+	push bc			;05ff  Save BC (OS configuration)
+	ld bc,00004h		;0600  Set count = 4 bytes
+	ldir			;0603  Copy 4 bytes: Monroe OS8 or CP/M system parameters
+	
+	; Set up for second OS parameter block copy
+	ld de,00023h		;0605  DE = destination address 0x0023 (OS parameter area)
+	ld hl,0ff8dh		;0608  HL = source in banked memory 0xFF8D (OS data block 2)
+	ld a,(0ff92h)		;060b  Load OS boot parameter 2 (system vectors, disk geometry)
+	ld (de),a		;060e  Store at 0x0023
+	inc de			;060f  DE = 0x0024
+	
+	; Copy second 4-byte OS parameter block
+	ld bc,00004h		;0610  Set count = 4 bytes  
+	ldir			;0613  Copy 4 bytes: Monroe OS8 system tables or CP/M BIOS tables
+	
+	pop bc			;0615  Restore BC (OS configuration)
+	jp (iy)			;0616  Jump to selected OS kernel entry point! (Monroe OS8 or CP/M)
+
+; ================================================================================
+; DATA TABLE AND DISK CONTROLLER INITIALIZATION
+; ================================================================================
+	defb 005h		;0618  Controller parameter 1
+	defb 080h		;0619  Controller parameter 2 (0x80 = enable flag?)
+	defb 005h		;061a  Controller parameter 3 
+	defb 000h		;061b  Controller parameter 4 (terminator?)
+
+; ================================================================================
+; DISK CONTROLLER SETUP AND STATUS CHECK ROUTINE
+; ================================================================================
+; Initializes the disk controller and waits for ready status
+; Uses the 4-byte parameter table above (0x0618-0x061B)
+; Returns: Carry set if timeout/error, clear if success
+
 sub_061ch:
-	ld bc,002a3h		;061c
-	ld hl,00618h		;061f
-	otir		;0622
-	ld b,0ffh		;0624
+	ld bc,002a3h		;061c  B=2 bytes, C=0xA3 (port number for disk controller)
+	ld hl,00618h		;061f  HL points to controller parameter table above
+	otir			;0622  Output 2 bytes from (HL) to port 0xA3, auto-increment HL
+	ld b,0ffh		;0624  B = 255 (timeout counter for controller ready)
+
 l0626h:
-	in a,(079h)		;0626
-	cp 0c7h		;0628
-	jr z,l0630h		;062a
-	djnz l0626h		;062c
-	scf			;062e
-	ret			;062f
+	; Wait for disk controller ready status
+	in a,(079h)		;0626  Read disk controller status port
+	cp 0c7h			;0628  Compare with ready status value 0xC7
+	jr z,l0630h		;062a  If ready (0xC7), continue with operation
+	djnz l0626h		;062c  Decrement timeout counter, loop if not expired
+	scf			;062e  Set carry flag (timeout error)
+	ret			;062f  Return with error
+
 l0630h:
-	call reading		;0630
-	ret c			;0633
-	in a,(0ffh)		;0634
-	rra			;0636
-	rra			;0637
-	and 007h		;0638
-	ld hl,007e2h		;063a
-	jr z,l064fh		;063d
-	ld hl,007d6h		;063f
-	dec a			;0642
-	jr z,l0648h		;0643
-	ld hl,007cah		;0645
+	; Controller is ready - execute read operation
+	call reading		;0630  Execute disk read command
+	ret c			;0633  Return if read error occurred
+	
+	; Analyze controller response for configuration
+	in a,(0ffh)		;0634  Read controller configuration register
+	rra			;0636  Rotate right (check bit 0)
+	rra			;0637  Rotate right again (check bit 1) 
+	and 007h		;0638  Mask to get lower 3 bits (configuration value 0-7)
+	
+	; *** BOOT DEVICE SELECTION LOGIC ***
+	; Configuration value determines boot device priority:
+	; 0 = Default (floppy-only system)
+	; 1 = Hard disk + floppy system (hard disk priority)  
+	; 2+ = Advanced hard disk system (hard disk with extended features)
+	
+	ld hl,007e2h		;063a  Default: point to floppy-only configuration table
+	jr z,l064fh		;063d  If value=0, use floppy-only mode, skip device selection
+	ld hl,007d6h		;063f  Point to hard disk + floppy configuration table
+	dec a			;0642  Decrement configuration value
+	jr z,l0648h		;0643  If value was 1, use hard disk + floppy mode
+	ld hl,007cah		;0645  Point to advanced hard disk configuration (value ≥ 2)
+
 l0648h:
-	call sub_076bh		;0648
-	call reading		;064b
-	ret c			;064e
+	call sub_076bh		;0648  Execute configuration-specific routine
+	call reading		;064b  Execute another disk read
+	ret c			;064e  Return if error
+
 l064fh:
-	ld de,0ff8dh		;064f
-	ld bc,00004h		;0652
-	ldir		;0655
-	jp l077fh		;0657
+	; Copy configuration data to system memory
+	ld de,0ff8dh		;064f  DE = destination in banked memory (system parameters)
+	ld bc,00004h		;0652  BC = 4 bytes to copy
+	ldir			;0655  Copy 4 bytes from (HL) to system memory
+	jp l077fh		;0657  Jump to next stage of disk initialization
+; ================================================================================
+; DISK COMMAND EXECUTION ROUTINE
+; ================================================================================
+; Executes specific floppy disk commands (0x10, 0x11) used during boot sequence
+; This routine handles low-level disk operations like recalibrate and seek
+; Input: C = disk command (0x10 = recalibrate, 0x11 = seek/position)
+; Output: Carry flag set if error, clear if success
+
 sub_065ah:
-	push bc			;065a
-	pop ix		;065b
-	ld a,010h		;065d
-	sub c			;065f
-	jr z,l0664h		;0660
-	ld a,020h		;0662
+	push bc			;065a  Save BC register
+	pop ix			;065b  IX = BC (save original command for later use)
+	ld a,010h		;065d  A = 0x10 (base command value)
+	sub c			;065f  A = 0x10 - C (calculate command offset)
+	jr z,l0664h		;0660  If C=0x10 (recalibrate), use A=0 parameter
+	ld a,020h		;0662  A = 0x20 (seek command parameter)
+
 l0664h:
-	ld hl,0ff83h		;0664
-	ld b,004h		;0667
-	ld (hl),008h		;0669
-	inc hl			;066b
-	ld (hl),a			;066c
+	; Build disk command parameter block
+	ld hl,0ff83h		;0664  Point to disk parameter buffer in banked memory
+	ld b,004h		;0667  B = 4 (number of parameters to set)
+	ld (hl),008h		;0669  Store 0x08 (command type/drive select)
+	inc hl			;066b  Move to next parameter slot
+	ld (hl),a		;066c  Store command-specific parameter (0x00 or 0x20)
+
 l066dh:
-	inc hl			;066d
-	ld (hl),000h		;066e
-	djnz l066dh		;0670
-	call reading		;0672
-	ret c			;0675
-	call moveoutreseta		;0676
-	call reading2		;0679
-	and 002h		;067c
-	ret z			;067e
-	scf			;067f
-	ret			;0680
-l0681h:
-	push bc			;0681
-	call screenclearnetry2		;0682
-	rst 10h			;0685
-
-; BLOCK 'ERROR1' (start 0x0686 end 0x06af)
+	; Clear remaining parameters
+	inc hl			;066d  Move to next parameter slot
+	ld (hl),000h		;066e  Clear parameter (set to 0x00)
+	djnz l066dh		;0670  Clear remaining 3 parameters (total 6 bytes)
+	
+	; Execute the disk command
+	call reading		;0672  Execute the prepared disk command
+	ret c			;0675  Return immediately if command failed
+	call moveoutreseta	;0676  Move/output result data  
+	call reading2		;0679  Read final status
+	and 002h		;067c  Check bit 1 (error flag)
+	ret z			;067e  Return success if bit 1 clear
+	scf			;067f  Set carry flag (error)
+	ret			;0680  Return with error
+; ================================================================================
+; CRITICAL DISK ERROR HANDLER  
+; ================================================================================
+; Handles severe disk system errors that prevent successful boot
+; This is called when disk controller hardware fails or becomes unresponsive
+; Displays Error #1 message and enters service mode
+
+print_error1:
+	push bc			;0681  Save BC register state
+	call screenclearnetry2		;0682  Clear screen and setup error display
+	rst 10h			;0685  RST 10h: Display error message (points to message below)
+
+; ================================================================================
+; ERROR #1 MESSAGE DATA - CRITICAL DISK SYSTEM ERROR
+; ================================================================================
+; "Error 1: Disk system error, Call Service" - 40 characters
+; This indicates hardware-level disk controller failure requiring service
+
 ERROR1_start:
-	defb 028h		;0686
-	defb 045h		;0687 count 40
-	defb 072h		;0688 Error 1: Disk system error, Call Service
-	defb 072h		;0689
-	defb 06fh		;068a
-	defb 072h		;068b
-	defb 020h		;068c
-	defb 031h		;068d
-	defb 03ah		;068e
-	defb 020h		;068f
-	defb 044h		;0690
-	defb 069h		;0691
-	defb 073h		;0692
-	defb 06bh		;0693
-	defb 020h		;0694
-	defb 073h		;0695
-	defb 079h		;0696
-	defb 073h		;0697
-	defb 074h		;0698
-	defb 065h		;0699
-	defb 06dh		;069a
-	defb 020h		;069b
-	defb 065h		;069c
-	defb 072h		;069d
-	defb 072h		;069e
-	defb 06fh		;069f
-	defb 072h		;06a0
-	defb 02ch		;06a1
-	defb 020h		;06a2
-	defb 043h		;06a3
-	defb 061h		;06a4
-	defb 06ch		;06a5
-	defb 06ch		;06a6
-	defb 020h		;06a7
-	defb 053h		;06a8
-	defb 065h		;06a9
-	defb 072h		;06aa
-	defb 076h		;06ab
-l06ach:
-	defb 069h		;06ac
-	defb 063h		;06ad
-	defb 065h		;06ae
+	defb 028h		;0686  Message length: 40 characters
+	defb 045h		;0687  'E'
+	defb 072h		;0688  'r'
+	defb 072h		;0689  'r'
+	defb 06fh		;068a  'o'
+	defb 072h		;068b  'r'
+	defb 020h		;068c  ' '
+	defb 031h		;068d  '1'
+	defb 03ah		;068e  ':'
+	defb 020h		;068f  ' '
+	defb 044h		;0690  'D'
+	defb 069h		;0691  'i'
+	defb 073h		;0692  's'
+	defb 06bh		;0693  'k'
+	defb 020h		;0694  ' '
+	defb 073h		;0695  's'
+	defb 079h		;0696  'y'
+	defb 073h		;0697  's'
+	defb 074h		;0698  't'
+	defb 065h		;0699  'e'
+	defb 06dh		;069a  'm'
+	defb 020h		;069b  ' '
+	defb 065h		;069c  'e'
+	defb 072h		;069d  'r'
+	defb 072h		;069e  'r'
+	defb 06fh		;069f  'o'
+	defb 072h		;06a0  'r'
+	defb 02ch		;06a1  ','
+	defb 020h		;06a2  ' '
+	defb 043h		;06a3  'C'
+	defb 061h		;06a4  'a'
+	defb 06ch		;06a5  'l'
+	defb 06ch		;06a6  'l'
+	defb 020h		;06a7  ' '
+	defb 053h		;06a8  'S'
+	defb 065h		;06a9  'e'
+	defb 072h		;06aa  'r'
+	defb 076h		;06ab  'v'
+	defb 069h		;06ac  'i'
+	defb 063h		;06ad  'c'
+	defb 065h		;06ae  'e'
 ERROR1_end:
-	call delayloop		;06af
-	call delayloop		;06b2
-	call delayloop		;06b5
-	call setupclearscreen2		;06b8
-	call readydisk		;06bb
-	pop bc			;06be
-	scf			;06bf
-	ret			;06c0
+
+; ================================================================================
+; ERROR RECOVERY AND SYSTEM RESTART
+; ================================================================================
+; After displaying the error, system performs cleanup and restart sequence
+
+error1_recovery:
+	call delayloop		;06af  Delay to allow user to read error message
+	call delayloop		;06b2  Additional delay for visibility
+	call delayloop		;06b5  Final delay before restart attempt
+	call setupclearscreen2	;06b8  Clear screen and reinitialize display system
+	call readydisk		;06bb  Attempt to ready disk system for retry
+	pop bc			;06be  Restore BC register from stack
+	scf			;06bf  Set carry flag (indicate error condition)
+	ret			;06c0  Return with error status
+
+; ================================================================================
+; DISK SECTOR READ WITH RETRY LOGIC
+; ================================================================================
+; Advanced disk read routine with automatic retry and error recovery
+; Input: D = sector count, BC = parameters, HL = buffer pointer
+; Output: Carry set if unrecoverable error, clear if success
+
 l06c1h:
-	call sub_04c7h		;06c1
-	ld a,b			;06c4
-	ld (0ff85h),a		;06c5
-	ld a,c			;06c8
-	ld (0ff86h),a		;06c9
+	call sub_04c7h		;06c1  Setup disk operation parameters
+	ld a,b			;06c4  Get B register (track/cylinder)
+	ld (0ff85h),a		;06c5  Store track parameter in system memory
+	ld a,c			;06c8  Get C register (sector/head)
+	ld (0ff86h),a		;06c9  Store sector parameter in system memory
+
 l06cch:
-	ld a,d			;06cc
-	ld (0ff87h),a		;06cd
-	push bc			;06d0
-	push hl			;06d1
-	call reading		;06d2
-	jp c,l06fbh		;06d5
-	ld hl,0ff83h		;06d8
-	ld bc,00678h		;06db
+	ld a,d			;06cc  Get D register (sector count)
+	ld (0ff87h),a		;06cd  Store sector count parameter
+	push bc			;06d0  Save BC registers (track/sector info)
+	push hl			;06d1  Save HL registers (buffer pointer)
+	call reading		;06d2  Execute disk read command
+	jp c,l06fbh		;06d5  If read error, jump to cleanup and return
+	
+	; Successful read - transfer parameter data
+	ld hl,0ff83h		;06d8  Point to disk parameter buffer
+	ld bc,00678h		;06db  B=6 bytes to transfer, C=0x78 (I/O port for data)
+
 l06deh:
-	in a,(079h)		;06de
-	and 041h		;06e0
-	jr nz,l06deh		;06e2
-	outi		;06e4
-	jr nz,l06deh		;06e6
-	out (07ah),a		;06e8
-	nop			;06ea
+	; Wait for controller ready and transfer data
+	in a,(079h)		;06de  Read disk controller status port
+	and 041h		;06e0  Check bits 6 and 0 (ready and data request flags)
+	jr nz,l06deh		;06e2  Wait until controller indicates ready for transfer
+	outi			;06e4  Transfer byte: output (HL) to port C, increment HL, decrement B
+	jr nz,l06deh		;06e6  Continue until all 6 parameter bytes transferred
+	out (07ah),a		;06e8  Write final control byte to data port 0x7A
+	nop			;06ea  Short timing delay for controller
+
 l06ebh:
-	in a,(079h)		;06eb
-	and 044h		;06ed
-	jr nz,l06ebh		;06ef
-	out (07bh),a		;06f1
-	call reading2		;06f3
-	and 002h		;06f6
-	call nz,sub_06ffh		;06f8
+	; Wait for final status and complete operation
+	in a,(079h)		;06eb  Read disk controller status
+	and 044h		;06ed  Check bits 6 and 2 (completion status flags)
+	jr nz,l06ebh		;06ef  Wait for completion status change
+	out (07bh),a		;06f1  Write completion status to control port 0x7B
+	call reading2		;06f3  Read final operation status
+	and 002h		;06f6  Check bit 1 (error indication)
+	call nz,sub_06ffh	;06f8  If error bit set, call error recovery routine
+
 l06fbh:
-	pop hl			;06fb
-	pop bc			;06fc
-	inc bc			;06fd
-	ret			;06fe
+	; Cleanup and return
+	pop hl			;06fb  Restore HL registers (buffer pointer)
+	pop bc			;06fc  Restore BC registers (track/sector)
+	inc bc			;06fd  Increment BC to next sector position
+	ret			;06fe  Return to caller
+
+; ================================================================================
+; ADVANCED DISK ERROR RECOVERY ROUTINE
+; ================================================================================
+; Sophisticated error recovery with retry logic and validation
+; Called when initial read fails - attempts recovery and validation
+; Returns: Carry set if unrecoverable, clear if recovery successful
+
 sub_06ffh:
-	call reading		;06ff
-	ret c			;0702
-	ld a,003h		;0703
-	call moveout		;0705
-	ld bc,00478h		;0708
-	ld hl,0ff89h		;070b
+	call reading		;06ff  Attempt another disk read operation
+	ret c			;0702  Return immediately if read still failing
+	ld a,003h		;0703  A = 3 (retry/recovery command code)
+	call moveout		;0705  Execute move/output operation with retry command
+	ld bc,00478h		;0708  B=4 bytes to read, C=0x78 (I/O data port)
+	ld hl,0ff89h		;070b  Point to error recovery buffer in system memory
+
 l070eh:
-	in a,(079h)		;070e
-	cp 00fh		;0710
-	jr nz,l070eh		;0712
-	ini		;0714
-	jr nz,l070eh		;0716
-	call reading2		;0718
-	ld a,(0ff89h)		;071b
-	sub 098h		;071e
-	ret z			;0720
-	scf			;0721
-	ret			;0722
+	; Read recovery data from controller
+	in a,(079h)		;070e  Read disk controller status port
+	cp 00fh			;0710  Compare with 0x0F (ready for data transfer)
+	jr nz,l070eh		;0712  Wait until controller indicates ready (status = 0x0F)
+	ini			;0714  Input byte: read from port C to (HL), increment HL, decrement B
+	jr nz,l070eh		;0716  Continue until all 4 recovery bytes read
+	call reading2		;0718  Read final status after recovery attempt
+	ld a,(0ff89h)		;071b  Get first byte from recovery buffer
+	sub 098h		;071e  Compare with expected recovery value 0x98
+	ret z			;0720  Return success (Z flag) if recovery data matches
+	scf			;0721  Set carry flag (recovery failed)
+	ret			;0722  Return with unrecoverable error status
+
+; ================================================================================
+; LOW-LEVEL DISK CONTROLLER COMMUNICATION ROUTINES
+; ================================================================================
+; Core routines for sending commands and reading status from disk controller
+
 reading:
-	in a,(079h)		;0723
-	and 080h		;0725
-	scf			;0727
-	ret z			;0728
-	ld a,001h		;0729
-	out (079h),a		;072b
-	ld b,0ffh		;072d
+	; Initiate disk read command with timeout protection
+	in a,(079h)		;0723  Read disk controller status port
+	and 080h		;0725  Check bit 7 (controller ready flag)
+	scf			;0727  Set carry flag (assume error initially)
+	ret z			;0728  Return with error if controller not ready
+	ld a,001h		;0729  A = 1 (start read command)
+	out (079h),a		;072b  Send start command to disk controller
+	ld b,0ffh		;072d  B = 255 (timeout counter - ~255 loop iterations)
+
 l072fh:
-	in a,(079h)		;072f
-	and 080h		;0731
-	ret z			;0733
-	djnz l072fh		;0734
-	scf			;0736
-	ret			;0737
+	; Wait for command completion with timeout
+	in a,(079h)		;072f  Read controller status port
+	and 080h		;0731  Check ready bit (bit 7)
+	ret z			;0733  Return success (carry clear) if ready bit cleared
+	djnz l072fh		;0734  Decrement timeout counter and continue waiting
+	scf			;0736  Set carry flag (timeout error)
+	ret			;0737  Return with timeout error
+
 reading2:
-	in a,(079h)		;0738
-	and 044h		;073a
-	jr nz,reading2		;073c
-	in a,(078h)		;073e
-	ld b,a			;0740
+	in a,(079h)		;0738  Read disk controller status
+	and 044h		;073a  Check bits 6 and 2 (busy/status flags)
+	jr nz,reading2		;073c  Wait until both flags clear
+	in a,(078h)		;073e  Read result from data port
+	ld b,a			;0740  Save result in B
+
 l0741h:
-	in a,(079h)		;0741
-	and 042h		;0743
-	jr nz,l0741h		;0745
-	in a,(078h)		;0747
-	ld a,b			;0749
-	ret			;074a
+	in a,(079h)		;0741  Read controller status again
+	and 042h		;0743  Check bits 6 and 1 (different status bits)
+	jr nz,l0741h		;0745  Wait until these flags clear
+	in a,(078h)		;0747  Read final data byte
+	ld a,b			;0749  Restore original result to A
+	ret			;074a  Return with status in A
+
+; ================================================================================
+; DISK COMMAND OUTPUT ROUTINES
+; ================================================================================
+; Send command sequences to disk controller
+
 moveoutreseta:
-	ld a,000h		;074b
+	ld a,000h		;074b  A = 0 (reset command)
+
 moveout:
-	call sub_0760h		;074d
-	ld a,(0ff84h)		;0750
-	call sub_0760h		;0753
-	ld a,000h		;0756
-	ld b,004h		;0758
+	call sub_0760h		;074d  Send A to disk controller
+	ld a,(0ff84h)		;0750  Get stored command parameter
+	call sub_0760h		;0753  Send parameter to controller
+	ld a,000h		;0756  A = 0 (padding/terminator)
+	ld b,004h		;0758  B = 4 (send 4 zero bytes)
+
 l075ah:
-	call sub_0760h		;075a
-	djnz l075ah		;075d
-	ret			;075f
+	call sub_0760h		;075a  Send zero byte to controller
+	djnz l075ah		;075d  Repeat 4 times
+	ret			;075f  Return
+
+; ================================================================================
+; LOW-LEVEL DISK CONTROLLER I/O
+; ================================================================================
+; Fundamental routine for sending bytes to disk controller
+
 sub_0760h:
-	push af			;0760
+	push af			;0760  Save byte to send
+	
 l0761h:
-	in a,(079h)		;0761
-	and 041h		;0763
-	jr nz,l0761h		;0765
-	pop af			;0767
-	out (078h),a		;0768
-	ret			;076a
+	in a,(079h)		;0761  Read controller status
+	and 041h		;0763  Check bits 6 and 0 (ready/busy flags)
+	jr nz,l0761h		;0765  Wait until controller ready to receive
+	pop af			;0767  Restore byte to send
+	out (078h),a		;0768  Send byte to controller data port
+	ret			;076a  Return
+
+; ================================================================================
+; DISK CONTROLLER DATA TRANSFER
+; ================================================================================
+; Transfers data block from controller
+
 sub_076bh:
-	ld a,00ch		;076b
-	call moveout		;076d
-	ld bc,00878h		;0770
+	ld a,00ch		;076b  A = 0x0C (data transfer command)
+	call moveout		;076d  Send command to controller
+	ld bc,00878h		;0770  B=8 bytes, C=0x78 (data port)
+
 l0773h:
-	in a,(079h)		;0773
-	cp 007h		;0775
-	jr nz,l0773h		;0777
-	outi		;0779
-	jr nz,l0773h		;077b
-	jr reading2		;077d
+	in a,(079h)		;0773  Read controller status
+	cp 007h			;0775  Compare with 0x07 (data ready)
+	jr nz,l0773h		;0777  Wait until data ready
+	outi			;0779  Input byte: (HL) ← (C), HL++, B--
+	jr nz,l0773h		;077b  Continue until 8 bytes transferred
+	jr reading2		;077d  Jump to read final status
+
+; ================================================================================
+; DISK ERROR RECOVERY AND ALTERNATE ROUTINES
+; ================================================================================
+
 l077fh:
-	ld a,0e4h		;077f
-	call steproutine		;0781
-	ret z			;0784
-	jp l0681h		;0785
+	ld a,0e4h		;077f  A = 0xE4 (error recovery command)
+	call steproutine	;0781  Execute step/recovery routine
+	ret z			;0784  Return if successful
+	jp print_error1		;0785  Jump to disk error handler
+
 l0788h:
-	call reading		;0788
-	ret c			;078b
-	ld a,001h		;078c
-	call steproutine		;078e
-	ret z			;0791
-	jr l079dh		;0792
+	call reading		;0788  Attempt disk read
+	ret c			;078b  Return if error
+	ld a,001h		;078c  A = 0x01 (step command)
+	call steproutine	;078e  Execute step routine
+	ret z			;0791  Return if successful
+	jr print_error3		;0792  Jump to alternate error handling
+
+; ================================================================================
+; DISK STEP/SEEK ROUTINE
+; ================================================================================
+; Executes disk step commands (seek operations)
+
 steproutine:
-	call moveout		;0794
-	call reading2		;0797
-	and 002h		;079a
-	ret			;079c
-l079dh:
-	call screenclearnetry2		;079d
-	rst 10h			;07a0
+	call moveout		;0794  Send step command to controller
+	call reading2		;0797  Read controller status
+	and 002h		;079a  Check bit 1 (error flag)
+	ret			;079c  Return with Z flag set if no error
+
+; ================================================================================
+; DISK MALFUNCTION ERROR HANDLER
+; ================================================================================
+
+print_error3:
+	call screenclearnetry2	;079d  Clear screen and setup display
+	rst 10h			;07a0  RST 10h: Display error message
+
+; ================================================================================
+; ERROR #3 MESSAGE DATA - DISK MALFUNCTION
+; ================================================================================
 
 ; BLOCK 'ERROR3' (start 0x07a1 end 0x07c9)
 ERROR3_start:
-	defb 027h		;07a1  count 39
-	defb 045h		;07a2 Error 3: Disk Malfunction, Call Service
-	defb 072h		;07a3
-	defb 072h		;07a4
-	defb 06fh		;07a5
-	defb 072h		;07a6
-	defb 020h		;07a7
-	defb 033h		;07a8
-	defb 03ah		;07a9
-	defb 020h		;07aa
-	defb 044h		;07ab
-	defb 069h		;07ac
-	defb 073h		;07ad
-	defb 06bh		;07ae
-	defb 020h		;07af
-	defb 04dh		;07b0
-	defb 061h		;07b1
-	defb 06ch		;07b2
-	defb 066h		;07b3
-	defb 075h		;07b4
-	defb 06eh		;07b5
-	defb 063h		;07b6
-	defb 074h		;07b7
-	defb 069h		;07b8
-	defb 06fh		;07b9
-	defb 06eh		;07ba
-	defb 02ch		;07bb
-	defb 020h		;07bc
-	defb 043h		;07bd
-	defb 061h		;07be
-	defb 06ch		;07bf
-	defb 06ch		;07c0
-	defb 020h		;07c1
-	defb 053h		;07c2
-	defb 065h		;07c3
-	defb 072h		;07c4
-	defb 076h		;07c5
-	defb 069h		;07c6
-	defb 063h		;07c7
-	defb 065h		;07c8
+	defb 027h		;07a1  Message length: 39 characters
+	defb 045h		;07a2  'E' - "Error #3: Disk Malfunction, Call Service"
+	defb 072h		;07a3  'r'
+	defb 072h		;07a4  'r'
+	defb 06fh		;07a5  'o'
+	defb 072h		;07a6  'r'
+	defb 020h		;07a7  ' '
+	defb 033h		;07a8  '3'
+	defb 03ah		;07a9  ':'
+	defb 020h		;07aa  ' '
+	defb 044h		;07ab  'D'
+	defb 069h		;07ac  'i'
+	defb 073h		;07ad  's'
+	defb 06bh		;07ae  'k'
+	defb 020h		;07af  ' '
+	defb 04dh		;07b0  'M'
+	defb 061h		;07b1  'a'
+	defb 06ch		;07b2  'l'
+	defb 066h		;07b3  'f'
+	defb 075h		;07b4  'u'
+	defb 06eh		;07b5  'n'
+	defb 063h		;07b6  'c'
+	defb 074h		;07b7  't'
+	defb 069h		;07b8  'i'
+	defb 06fh		;07b9  'o'
+	defb 06eh		;07ba  'n'
+	defb 02ch		;07bb  ','
+	defb 020h		;07bc  ' '
+	defb 043h		;07bd  'C'
+	defb 061h		;07be  'a'
+	defb 06ch		;07bf  'l'
+	defb 06ch		;07c0  'l'
+	defb 020h		;07c1  ' '
+	defb 053h		;07c2  'S'
+	defb 065h		;07c3  'e'
+	defb 072h		;07c4  'r'
+	defb 076h		;07c5  'v'
+	defb 069h		;07c6  'i'
+	defb 063h		;07c7  'c'
+	defb 065h		;07c8  'e'
 ERROR3_end:
-	halt			;07c9
+	halt			;07c9  System halt - requires service intervention
+
+; ================================================================================
+; DATA TABLES AND CONSTANTS
+; ================================================================================
+; Various data tables used by system routines
+
 l07cah:
-	ld bc,00432h		;07ca
-	ld bc,00031h		;07cd
-	ld b,b			;07d0
-	dec bc			;07d1
-	ld b,000h		;07d2
-	sub l			;07d4
-	rst 38h			;07d5
-l07d6h:
-	ld bc,00232h		;07d6
-	ld bc,00031h		;07d9
-	ld b,b			;07dc
-	dec bc			;07dd
-	ld b,000h		;07de
-	ld c,d			;07e0
-	rst 38h			;07e1
+	defb 001h		;07ca  Data table entry 1
+	defb 032h		;07cb  Data table entry 2
+	defb 004h		;07cc  Data table entry 3
+	defb 001h		;07cd  Data table entry 4
+	defb 031h		;07ce  Data table entry 5
+	defb 000h		;07cf  Data table entry 6
+	defb 040h		;07d0  Data byte
+	defb 00bh		;07d1  Data byte
+	defb 006h		;07d2  Data byte
+	defb 000h		;07d3  Data byte
+	defb 095h		;07d4  Data byte
+	defb 0ffh		;07d5  Data byte
+	defb 001h		;07d6  Data byte
+l07d7h:
+	defb 032h		;07d7  Data byte
+	defb 002h		;07d8  Data byte  
+	defb 001h		;07d9  Data byte
+	defb 031h		;07da  Data table entry 1
+	defb 000h		;07db  Data table entry 1
+	defb 040h		;07dc  Data table entry 2
+	defb 00bh		;07dd  Data table entry 2
+	defb 006h		;07de  Data byte
+	defb 000h		;07df  Data byte
+	defb 04ah		;07e0  Data byte
+	defb 0ffh		;07e1  Data byte
+
 l07e2h:
-	nop			;07e2
-	nop			;07e3
-	ld c,d			;07e4
-	rst 38h			;07e5
-	rst 38h			;07e6
-	rst 38h			;07e7
-	rst 38h			;07e8
-	rst 38h			;07e9
-	rst 38h			;07ea
-	rst 38h			;07eb
-	rst 38h			;07ec
-	rst 38h			;07ed
-	rst 38h			;07ee
-	rst 38h			;07ef
-	rst 38h			;07f0
-	rst 38h			;07f1
-	rst 38h			;07f2
-	rst 38h			;07f3
-	rst 38h			;07f4
-	rst 38h			;07f5
-	rst 38h			;07f6
-	rst 38h			;07f7
-	rst 38h			;07f8
-	rst 38h			;07f9
-	rst 38h			;07fa
-	rst 38h			;07fb
-	rst 38h			;07fc
-	rst 38h			;07fd
-	rst 38h			;07fe
-	rst 38h			;07ff
+	defb 000h		;07e2  Data byte 'Q'
+	defb 000h		;07e3  Data byte (NOP padding)
+	defb 04ah		;07e4  Data byte (NOP padding)
+l07e5h:
+	defb 0ffh		;07e5  Data byte 'J'
+	
+; ROM unused space filled with RST 38h (0FFh) - typical EPROM pattern
+
+	defb 0ffh		;07e6  Unused ROM space
+	defb 0ffh		;07e7  Unused ROM space
+	defb 0ffh		;07e8  Unused ROM space
+	defb 0ffh		;07e9  Unused ROM space
+	defb 0ffh		;07ea  Unused ROM space
+	defb 0ffh		;07eb  Unused ROM space
+	defb 0ffh		;07ec  Unused ROM space
+	defb 0ffh		;07ed  Unused ROM space
+	defb 0ffh		;07ee  Unused ROM space
+	defb 0ffh		;07ef  Unused ROM space
+	defb 0ffh		;07f0  Unused ROM space
+	defb 0ffh		;07f1  Unused ROM space
+	defb 0ffh		;07f2  Unused ROM space
+	defb 0ffh		;07f3  Unused ROM space
+	defb 0ffh		;07f4  Unused ROM space
+	defb 0ffh		;07f5  Unused ROM space
+	defb 0ffh		;07f6  Unused ROM space
+	defb 0ffh		;07f7  Unused ROM space
+	defb 0ffh		;07f8  Unused ROM space
+	defb 0ffh		;07f9  Unused ROM space
+	defb 0ffh		;07fa  Unused ROM space
+	defb 0ffh		;07fb  Unused ROM space
+	defb 0ffh		;07fc  Unused ROM space
+	defb 0ffh		;07fd  Unused ROM space
+	defb 0ffh		;07fe  Unused ROM space
+	defb 0ffh		;07ff  End of 2K ROM - TMS2516 EPROM
+
+; ================================================================================
+; END OF ROM - MONROE OC8820 BOOT ROM R3.00C
+; ================================================================================
+; Total ROM size: 2048 bytes (0x0000-0x07FF)
+; Boot process complete - system transfers control to OS at 0xFFA6
+; ================================================================================

pcb/databoard_5076/databoard_5076.kicad_pro

@@ -529,11 +529,23 @@
           "label": "DNP",
           "name": "${DNP}",
           "show": true
+        },
+        {
+          "group_by": false,
+          "label": "#",
+          "name": "${ITEM_NUMBER}",
+          "show": false
+        },
+        {
+          "group_by": false,
+          "label": "Description",
+          "name": "Description",
+          "show": false
         }
       ],
       "filter_string": "",
       "group_symbols": true,
-      "name": "Grouped By Value",
+      "name": "",
       "sort_asc": true,
       "sort_field": "Reference"
     },

pcb/databoard_5076/databoard_5076.kicad_sch

@@ -22582,6 +22582,16 @@
 		)
 		(uuid "ffc0ce75-be8f-40b5-b5fb-098287bcaab1")
 	)
+	(text "B7 ~{INT6} shall be connect to interupt on the 4105 A5 ~{INT} på 4105 \nby wiring on the backplane on the 4680 bus"
+		(exclude_from_sim no)
+		(at 428.752 215.9 0)
+		(effects
+			(font
+				(size 1.27 1.27)
+			)
+		)
+		(uuid "805b891f-ed0c-4d60-a81a-baf6c48cd5f2")
+	)
 	(label "~{INT4}"
 		(at 373.38 227.33 0)
 		(fields_autoplaced yes)
@@ -25422,7 +25432,7 @@
 				(justify left)
 			)
 		)
-		(property "Value" "8205"
+		(property "Value" "DS8205"
 			(at 242.2241 62.611 0)
 			(effects
 				(font
@@ -33538,7 +33548,7 @@
 				(justify left)
 			)
 		)
-		(property "Value" "8205"
+		(property "Value" "DS8205"
 			(at 233.3341 135.001 0)
 			(effects
 				(font

pic/rgb2hdi_profile.txt

@@ -0,0 +1,6 @@
+sampling=1,1,1,1,1,1,1,0,1,0,5,0,0,0,0,0,0,1,0,0,100,256,100,256,100,256,256,256
+geometry=72,0,832,316,880,314,4,4,0,0,18000181,954,5000,315,1,0,1
+palette=Mono_(2_level)
+scanline_level=0
+screencap_size=1
+genlock_mode=1