From dd159cc607d10cb5ff2f1bf7eac927f8524e1ad7 Mon Sep 17 00:00:00 2001
From: Maciej Witkowiak <ytm@elysium.pl>
Date: Fri, 22 Mar 2024 22:11:25 +0100
Subject: [PATCH 01/27] 1541 ROM calls documented using All About Your 1541
 http://unusedino.de/ec64/technical/aay/c1541/index.htm

---
 drv/drv1541.s | 24 ++++++++++++------------
 1 file changed, 12 insertions(+), 12 deletions(-)

diff --git a/drv/drv1541.s b/drv/drv1541.s
index 378f303b..b26cd8f7 100644
--- a/drv/drv1541.s
+++ b/drv/drv1541.s
@@ -1298,7 +1298,7 @@ Drv_ExitTurbo:
 	jsr D_DUNK4_1
 	LoadB $33, 0
 	sta $1800
-	jsr $f98f
+	jsr $f98f			; turn drive motor off
 	LoadB $1c0c, $ec
 	pla
 	pla
@@ -1435,7 +1435,7 @@ Drv_NewDisk_4:
 Drv_NewDisk_5:
 	txa
 Drv_NewDisk_6:
-	jsr $f24b
+	jsr $f24b			; Establish number of sectors per track (in: A=track, out: A=number of sectors on that track)
 	sta $43
 Drv_NewDisk_7:
 	lda $1c00
@@ -1528,11 +1528,11 @@ D_DUNK11_1:
 	beq D_DUNK11_3
 	cmp #$30
 	beq D_DUNK11_2
-	jmp $f4ca
+	jmp $f4ca				; Test command code further ($00=read, $10=write, $20=verify, other=read block header)
 D_DUNK11_2:
-	jmp $f3b1
+	jmp $f3b1				; Read block header, verify ID
 D_DUNK11_3:
-	jsr $f5e9
+	jsr $f5e9				; Calculate parity for data buffer ($30)
 	sta $3a
 	lda $1c00
 	and #$10
@@ -1540,11 +1540,11 @@ D_DUNK11_3:
 	lda #$08
 	bne D_DUNK11_9
 D_DUNK11_4:
-	jsr $f78f
-	jsr $f510
+	jsr $f78f				; Convert 260 bytes (256+4) to 325 bytes group code buffer $01BB-$01FF and ($30)
+	jsr $f510				; Read block header (wait until needed block header arrives)
 	ldx #9
 D_DUNK11_5:
-	bvc D_DUNK11_5
+	bvc D_DUNK11_5				; skip over sync
 	clv
 	dex
 	bne D_DUNK11_5
@@ -1565,14 +1565,14 @@ D_DUNK11_6:
 	bne D_DUNK11_6
 	ldy #$bb
 D_DUNK11_7:
-	lda $0100,y
+	lda $0100,y				; write data
 	bvc *
 	clv
 	sta $1c01
 	iny
 	bne D_DUNK11_7
 D_DUNK11_8:
-	lda ($30),y
+	lda ($30),y				; write data, continued
 	bvc *
 	clv
 	sta $1c01
@@ -1593,9 +1593,9 @@ D_DUNK12:
 	lda $20
 	and #$20
 	bne D_DUNK12_3
-	jsr $f97e
+	jsr $f97e				; Turn drive motor on
 D_DUNK12_1:
-	ldy #$80
+	ldy #$80				; delay until it spins up
 D_DUNK12_2:
 	dex
 	bne D_DUNK12_2

From 48b2cc283a57cb43898cb3fea1d33b4dad1642c8 Mon Sep 17 00:00:00 2001
From: Maciej Witkowiak <ytm@elysium.pl>
Date: Sat, 23 Mar 2024 12:20:47 +0100
Subject: [PATCH 02/27] 1541 disk driver with serial communication replaced by
 parallel (standard: VIA pins 2-9,18,39) cable

---
 Makefile                |    5 +
 config.inc              |    2 +
 drv/drv1541parallel.cfg |   11 +
 drv/drv1541parallel.s   | 1552 +++++++++++++++++++++++++++++++++++++++
 4 files changed, 1570 insertions(+)
 mode change 100755 => 100644 Makefile
 create mode 100644 drv/drv1541parallel.cfg
 create mode 100644 drv/drv1541parallel.s

diff --git a/Makefile b/Makefile
old mode 100755
new mode 100644
index 5e4d6636..6c918043
--- a/Makefile
+++ b/Makefile
@@ -233,6 +233,7 @@ endif
 
 DRIVER_SOURCES= \
 	drv/drv1541.bin \
+	drv/drv1541parallel.bin \
 	drv/drv1571.bin \
 	drv/drv1581.bin \
 	input/joydrv.bin \
@@ -269,6 +270,7 @@ PREFIXED_RELOCATOR_OBJS = $(addprefix $(BUILD_DIR)/, $(RELOCATOR_OBJS))
 ALL_BINS= \
 	$(BUILD_DIR)/kernal/kernal.bin \
 	$(BUILD_DIR)/drv/drv1541.bin \
+	$(BUILD_DIR)/drv/drv1541parallel.bin \
 	$(BUILD_DIR)/drv/drv1571.bin \
 	$(BUILD_DIR)/drv/drv1581.bin \
 	$(BUILD_DIR)/input/joydrv.bin \
@@ -379,6 +381,9 @@ endif
 $(BUILD_DIR)/drv/drv1541.bin: $(BUILD_DIR)/drv/drv1541.o drv/drv1541.cfg $(DEPS)
 	$(LD) -C drv/drv1541.cfg $(BUILD_DIR)/drv/drv1541.o -o $@
 
+$(BUILD_DIR)/drv/drv1541parallel.bin: $(BUILD_DIR)/drv/drv1541parallel.o drv/drv1541parallel.cfg $(DEPS)
+	$(LD) -C drv/drv1541parallel.cfg $(BUILD_DIR)/drv/drv1541parallel.o -o $@
+
 $(BUILD_DIR)/drv/drv1571.bin: $(BUILD_DIR)/drv/drv1571.o drv/drv1571.cfg $(DEPS)
 	$(LD) -C drv/drv1571.cfg $(BUILD_DIR)/drv/drv1571.o -o $@
 
diff --git a/config.inc b/config.inc
index eca79b6a..b028f71f 100755
--- a/config.inc
+++ b/config.inc
@@ -168,6 +168,8 @@ REUPresent = 1
 
 .if .defined(drv1541)
 DRV_TYPE = 1 ; DRV_1541
+.elseif .defined(drv1541parallel)
+DRV_TYPE = 1; DRV_1541
 .elseif .defined(drv1571)
 DRV_TYPE = 2; DRV_1571
 .elseif .defined(drv1581)
diff --git a/drv/drv1541parallel.cfg b/drv/drv1541parallel.cfg
new file mode 100644
index 00000000..25d05603
--- /dev/null
+++ b/drv/drv1541parallel.cfg
@@ -0,0 +1,11 @@
+MEMORY {
+	DISK_BASE:    start = $9000, size = $0D80, file = %O;
+
+	DRIVE0300:    start = $0300, size = $0500;
+}
+
+SEGMENTS {
+	drv1541:            load = DISK_BASE, type = ro;
+	drv1541_drivecode:  load = DISK_BASE, run = DRIVE0300, type = ro;
+	drv1541_b:          load = DISK_BASE, type = ro;
+}
diff --git a/drv/drv1541parallel.s b/drv/drv1541parallel.s
new file mode 100644
index 00000000..023dcf12
--- /dev/null
+++ b/drv/drv1541parallel.s
@@ -0,0 +1,1552 @@
+; GEOS by Berkeley Softworks
+; reverse engineered by Maciej Witkowiak, Michael Steil
+;
+; Commodore 1541 disk driver with parallel cable
+
+.include "const.inc"
+.include "geossym.inc"
+.include "geosmac.inc"
+.include "config.inc"
+.include "kernal.inc"
+.include "jumptab.inc"
+.include "c64.inc"
+
+.segment "drv1541"
+
+DriveAddy = $0300
+
+_InitForIO:
+	.word __InitForIO
+_DoneWithIO:
+	.word __DoneWithIO
+_ExitTurbo:
+	.word __ExitTurbo
+_PurgeTurbo:
+	.word __PurgeTurbo
+_EnterTurbo:
+	.word __EnterTurbo
+_ChangeDiskDevice:
+	.word __ChangeDiskDevice
+_NewDisk:
+	.word __NewDisk
+_ReadBlock:
+	.word __ReadBlock
+_WriteBlock:
+	.word __WriteBlock
+_VerWriteBlock:
+	.word __VerWriteBlock
+_OpenDisk:
+	.word __OpenDisk
+_GetBlock:
+	.word __GetBlock
+_PutBlock:
+	.word __PutBlock
+_GetDirHead:
+	.word __GetDirHead
+_PutDirHead:
+	.word __PutDirHead
+_GetFreeDirBlk:
+	.word __GetFreeDirBlk
+_CalcBlksFree:
+	.word __CalcBlksFree
+_FreeBlock:
+	.word __FreeBlock
+_SetNextFree:
+	.word __SetNextFree
+_FindBAMBit:
+	.word __FindBAMBit
+_NxtBlkAlloc:
+	.word __NxtBlkAlloc
+_BlkAlloc:
+	.word __BlkAlloc
+_ChkDkGEOS:
+	.word __ChkDkGEOS
+_SetGEOSDisk:
+	.word __SetGEOSDisk
+
+Get1stDirEntry:
+	jmp _Get1stDirEntry
+GetNxtDirEntry:
+	jmp _GetNxtDirEntry
+GetBorder:
+	jmp _GetBorder
+AddDirBlock:
+	jmp _AddDirBlock
+ReadBuff:
+	jmp _ReadBuff
+WriteBuff:
+	jmp _WriteBuff
+	jmp DUNK4_2
+	jmp GetDOSError
+AllocateBlock:
+	jmp _AllocateBlock
+ReadLink:
+	jmp _ReadLink
+
+__GetDirHead:
+	jsr SetDirHead
+	bne __GetBlock
+_ReadBuff:
+	LoadW r4, diskBlkBuf
+__GetBlock:
+	jsr EnterTurbo
+	bnex GetBlk0
+	jsr InitForIO
+	jsr ReadBlock
+	jsr DoneWithIO
+GetBlk0:
+	rts
+
+__PutDirHead:
+	jsr SetDirHead
+	bne __PutBlock
+_WriteBuff:
+	LoadW r4, diskBlkBuf
+__PutBlock:
+	jsr EnterTurbo
+	bnex PutBlk1
+	jsr InitForIO
+	jsr WriteBlock
+	bnex PutBlk0
+	jsr VerWriteBlock
+PutBlk0:
+	jsr DoneWithIO
+PutBlk1:
+	rts
+
+SetDirHead:
+	LoadB r1L, DIR_TRACK
+	LoadB r1H, 0
+	sta r4L
+	LoadB r4H, (>curDirHead)
+	rts
+
+CheckParams:
+	bbrf 6, curType, CheckParams_1
+	jsr DoCacheVerify
+	beq CheckParams_2
+CheckParams_1:
+	lda #0
+	sta errCount
+	ldx #INV_TRACK
+	lda r1L
+	beq CheckParams_2
+	cmp #N_TRACKS+1
+	bcs CheckParams_2
+	sec
+	rts
+CheckParams_2:
+	clc
+	rts
+
+__OpenDisk:
+	ldy curDrive
+	lda _driveType,y
+	sta tmpDriveType
+	and #%10111111
+	sta _driveType,y
+	jsr NewDisk
+	bnex OpenDsk1
+	jsr GetDirHead
+	bnex OpenDsk1
+	bbrf 6, tmpDriveType, OpenDsk0
+	jsr DoCacheVerify
+	beq OpenDsk0
+	jsr DoClearCache
+	jsr SetDirHead
+	jsr DoCacheWrite
+OpenDsk0:
+	LoadW r5, curDirHead
+	jsr ChkDkGEOS
+	LoadW r4, curDirHead+OFF_DISK_NAME
+	ldx #r5
+	jsr GetPtrCurDkNm
+	ldx #r4
+	ldy #r5
+	lda #18
+	jsr CopyFString
+	ldx #0
+OpenDsk1:
+	lda tmpDriveType
+	ldy curDrive
+	sta _driveType,y
+	rts
+tmpDriveType:
+	.byte 0
+
+__BlkAlloc:
+	ldy #1
+	sty r3L
+	dey
+	sty r3H
+__NxtBlkAlloc:
+	PushW r9
+	PushW r3
+	LoadW r3, $00fe
+	ldx #r2
+	ldy #r3
+	jsr Ddiv
+	lda r8L
+	beq BlkAlc0
+	inc r2L
+	bne BlkAlc0
+	inc r2H
+BlkAlc0:
+	LoadW r5, curDirHead
+	jsr CalcBlksFree
+	PopW r3
+	ldx #INSUFF_SPACE
+	CmpW r2, r4
+	beq BlkAlc1
+	bcs BlkAlc4
+BlkAlc1:
+	MoveW r6, r4
+	MoveW r2, r5
+BlkAlc2:
+	jsr SetNextFree
+	bnex BlkAlc4
+	ldy #0
+	lda r3L
+	sta (r4),y
+	iny
+	lda r3H
+	sta (r4),y
+	AddVW 2, r4
+	lda r5L
+	bne @X
+	dec r5H
+@X:	dec r5L
+	lda r5L
+	ora r5H
+	bne BlkAlc2
+	ldy #0
+	tya
+	sta (r4),y
+	iny
+	lda r8L
+	bne BlkAlc3
+	lda #$fe
+BlkAlc3:
+	clc
+	adc #1
+	sta (r4),y
+	ldx #0
+BlkAlc4:
+	PopW r9
+	rts
+
+_Get1stDirEntry:
+	LoadB r1L, DIR_TRACK
+	LoadB r1H, 1
+	jsr ReadBuff
+	LoadW r5, diskBlkBuf+FRST_FILE_ENTRY
+	lda #0
+	sta borderFlag
+	rts
+
+_GetNxtDirEntry:
+	ldx #0
+	ldy #0
+	AddVW $20, r5
+	CmpWI r5, diskBlkBuf+$ff
+	bcc GNDirEntry1
+	ldy #$ff
+	MoveW diskBlkBuf, r1
+	bne GNDirEntry0
+	lda borderFlag
+	bne GNDirEntry1
+	lda #$ff
+	sta borderFlag
+	jsr GetBorder
+	bnex GNDirEntry1
+	tya
+	bne GNDirEntry1
+GNDirEntry0:
+	jsr ReadBuff
+	ldy #0
+	LoadW r5, diskBlkBuf+FRST_FILE_ENTRY
+GNDirEntry1:
+	rts
+
+_GetBorder:
+	jsr GetDirHead
+	bnex GetBord2
+	LoadW r5, curDirHead
+	jsr ChkDkGEOS
+	bne GetBord0
+	ldy #$ff
+	bne GetBord1
+GetBord0:
+	MoveW curDirHead+OFF_OP_TR_SC, r1
+	ldy #0
+GetBord1:
+	ldx #0
+GetBord2:
+	rts
+
+__ChkDkGEOS:
+	ldy #OFF_GS_ID
+	ldx #0
+	LoadB isGEOS, 0
+ChkDkG0:
+	lda (r5),y
+	cmp GEOSDiskID,x
+	bne ChkDkG1
+	iny
+	inx
+	cpx #11
+	bne ChkDkG0
+	LoadB isGEOS, $ff
+ChkDkG1:
+	lda isGEOS
+	rts
+
+GEOSDiskID:
+	.byte "GEOS format V1.0",NULL
+
+__GetFreeDirBlk:
+	php
+	sei
+	PushB r6L
+	PushW r2
+	ldx r10L
+	inx
+	stx r6L
+	LoadB r1L, DIR_TRACK
+	LoadB r1H, 1
+GFDirBlk0:
+	jsr ReadBuff
+GFDirBlk1:
+	bnex GFDirBlk5
+	dec r6L
+	beq GFDirBlk3
+GFDirBlk11:
+	lda diskBlkBuf
+	bne GFDirBlk2
+	jsr AddDirBlock
+	bra GFDirBlk1
+GFDirBlk2:
+	sta r1L
+	MoveB diskBlkBuf+1, r1H
+	bra GFDirBlk0
+GFDirBlk3:
+	ldy #FRST_FILE_ENTRY
+	ldx #0
+GFDirBlk4:
+	lda diskBlkBuf,y
+	beq GFDirBlk5
+	tya
+	addv $20
+	tay
+	bcc GFDirBlk4
+	LoadB r6L, 1
+	ldx #FULL_DIRECTORY
+	ldy r10L
+	iny
+	sty r10L
+	cpy #$12
+	bcc GFDirBlk11
+GFDirBlk5:
+	PopW r2
+	PopB r6L
+	plp
+	rts
+
+_AddDirBlock:
+	PushW r6
+	ldy #$48
+	ldx #FULL_DIRECTORY
+	lda curDirHead,y
+	beq ADirBlk0
+	MoveW r1, r3
+	jsr SetNextFree
+	MoveW r3, diskBlkBuf
+	jsr WriteBuff
+	bnex ADirBlk0
+	MoveW r3, r1
+	jsr ClearAndWrite
+ADirBlk0:
+	PopW r6
+	rts
+
+ClearAndWrite:
+	lda #0
+	tay
+CAndWr0:
+	sta diskBlkBuf,y
+	iny
+	bne CAndWr0
+	dey
+	sty diskBlkBuf+1
+	jmp WriteBuff
+
+__SetNextFree:
+	lda r3H
+	add interleave
+	sta r6H
+	MoveB r3L, r6L
+	cmp #25
+	bcc SNxtFree0
+	dec r6H
+SNxtFree0:
+	cmp #DIR_TRACK
+	beq SNxtFree1
+SNxtFree00:
+	lda r6L
+	cmp #DIR_TRACK
+	beq SNxtFree3
+SNxtFree1:
+	asl
+	asl
+	tax
+	lda curDirHead,x
+	beq SNxtFree3
+	lda r6L
+	jsr SNxtFreeHelp
+	lda SecScTab,x
+	sta r7L
+	tay
+SNxtFree2:
+	jsr SNxtFreeHelp2
+	beq SNxtFree4
+	inc r6H
+	dey
+	bne SNxtFree2
+SNxtFree3:
+	inc r6L
+	CmpBI r6L, N_TRACKS+1
+	bcs SNxtFree5
+	sub r3L
+	sta r6H
+	asl
+	adc #4
+	adc interleave
+	sta r6H
+	bra SNxtFree00
+SNxtFree4:
+	MoveW_ r6, r3
+	ldx #0
+	rts
+SNxtFree5:
+	ldx #INSUFF_SPACE
+	rts
+
+SNxtFreeHelp:
+	ldx #0
+SNFHlp0:
+	cmp SecTrTab,x
+	bcc SNFHlp1
+	inx
+	bne SNFHlp0
+SNFHlp1:
+	rts
+
+SecTrTab:
+	.byte 18, 25, 31, 36
+SecScTab:
+	.byte 21, 19, 18, 17
+
+SNxtFreeHelp2:
+	lda r6H
+SNFHlp2_1:
+	cmp r7L
+	bcc SNFHlp2_2
+	sub r7L
+	bra SNFHlp2_1
+SNFHlp2_2:
+	sta r6H
+
+_AllocateBlock:
+	jsr FindBAMBit
+	beq SNFHlp2_3
+	lda r8H
+	eor #$ff
+	and curDirHead,x
+	sta curDirHead,x
+	ldx r7H
+	dec curDirHead,x
+	ldx #0
+	rts
+SNFHlp2_3:
+	ldx #BAD_BAM
+	rts
+
+__FindBAMBit:
+	lda r6L
+	asl
+	asl
+	sta r7H
+	lda r6H
+	and #%00000111
+	tax
+	lda FBBBitTab,x
+	sta r8H
+	lda r6H
+	lsr
+	lsr
+	lsr
+	sec
+	adc r7H
+	tax
+	lda curDirHead,x
+	and r8H
+	rts
+
+FBBBitTab:
+	.byte $01, $02, $04, $08
+	.byte $10, $20, $40, $80
+
+__FreeBlock:
+	jsr FindBAMBit
+	bne FreeBlk0
+	lda r8H
+	eor curDirHead,x
+	sta curDirHead,x
+	ldx r7H
+	inc curDirHead,x
+	ldx #0
+	rts
+FreeBlk0:
+	ldx #BAD_BAM
+	rts
+
+__CalcBlksFree:
+	LoadW_ r4, 0
+	ldy #OFF_TO_BAM
+CBlksFre0:
+	lda (r5),y
+	add r4L
+	sta r4L
+	bcc CBlksFre1
+	inc r4H
+CBlksFre1:
+	tya
+	clc
+	adc #4
+	tay
+	cpy #$48
+	beq CBlksFre1
+	cpy #$90
+	bne CBlksFre0
+	LoadW r3, $0298
+	rts
+
+__SetGEOSDisk:
+	jsr GetDirHead
+	bnex SetGDisk2
+	LoadW r5, curDirHead
+	jsr CalcBlksFree
+	ldx #INSUFF_SPACE
+	lda r4L
+	ora r4H
+	beq SetGDisk2
+	LoadB r3L, DIR_TRACK+1
+	LoadB r3H, 0
+	jsr SetNextFree
+	beqx SetGDisk0
+	LoadB r3L, 1
+	jsr SetNextFree
+	bnex SetGDisk2
+SetGDisk0:
+	MoveW r3, r1
+	jsr ClearAndWrite
+	bnex SetGDisk2
+	MoveW r1, curDirHead+OFF_OP_TR_SC
+	ldy #OFF_GS_ID+15
+	ldx #15
+SetGDisk1:
+	lda GEOSDiskID,x
+	sta curDirHead,y
+	dey
+	dex
+	bpl SetGDisk1
+	jsr PutDirHead
+SetGDisk2:
+	rts
+
+__InitForIO:
+	php
+	PopB tmpPS
+	sei
+	MoveB CPU_DATA, tmpCPU_DATA
+.ifndef bsw128
+	LoadB CPU_DATA, KRNL_IO_IN
+.endif
+	MoveB grirqen, tmpgrirqen
+	MoveB clkreg, tmpclkreg
+	ldy #0
+	sty clkreg
+	sty grirqen
+	lda #%01111111
+	sta grirq
+	sta cia1base+13
+	sta cia2base+13
+	lda #>D_IRQHandler
+	sta irqvec+1
+.ifdef bsw128
+	sta nmivec+1
+.endif
+	lda #<D_IRQHandler
+	sta irqvec
+.ifndef bsw128
+	lda #>D_NMIHandler
+	sta nmivec+1
+	lda #<D_NMIHandler
+.endif
+	sta nmivec
+	LoadB cia2base+2, %00111111
+	MoveB mobenble, tmpmobenble
+	sty mobenble
+	sty cia2base+5
+	iny
+	sty cia2base+4
+	LoadB cia2base+13, %10000001
+	LoadB cia2base+14, %00001001
+	LoadB cia2base+3, $00	; user port input
+	lda cia2base+13		; clear /FLAG
+	rts
+
+D_IRQHandler:
+.ifdef bsw128
+	PopB $ff00
+.endif
+	pla
+	tay
+	pla
+	tax
+	pla
+D_NMIHandler:
+	rti
+
+__DoneWithIO:
+	sei
+	MoveB tmpclkreg, clkreg
+	MoveB tmpmobenble, mobenble
+	LoadB cia2base+13, %01111111
+	lda cia2base+13
+	MoveB tmpgrirqen, grirqen
+.ifndef bsw128
+	MoveB tmpCPU_DATA, CPU_DATA
+.endif
+	PushB tmpPS
+	plp
+	rts
+
+Hst_RecvByte:
+Hst_RecvByte_0:
+:	lda cia2base+13		; wait for flag
+	beq :-
+	lda cia2base+1		; read data
+	dey
+	sta (z8b),y
+	bne Hst_RecvByte_0
+	rts
+
+Hst_SendByte:
+	tya
+	pha
+	ldy #$ff
+	sty cia2base+3			; port B output
+	iny
+	jsr Hst_SendByte_01
+	pla
+	tay
+	LoadB cia2base+3, $ff		; port B output
+Hst_SendByte_0:
+	dey
+	lda (z8b),y
+Hst_SendByte_01:
+	sta cia2base+1			; write
+:	lda cia2base+13			; wait for handshake
+	beq :-
+	cpy #0
+	bne Hst_SendByte_0
+	LoadB cia2base+3, $00		; port B input
+	rts
+
+SendDOSCmd:
+	stx z8c
+	sta z8b
+	LoadB STATUS, 0
+	lda curDrive
+	jsr $ffb1
+	bbsf 7, STATUS, SndDOSCmd1
+	lda #$ff
+	jsr $ff93
+	bbsf 7, STATUS, SndDOSCmd1
+	ldy #0
+SndDOSCmd0:
+	lda (z8b),y
+	jsr $ffa8
+	iny
+	cpy #5
+	bcc SndDOSCmd0
+	ldx #0
+	rts
+SndDOSCmd1:
+	jsr $ffae
+	ldx #DEV_NOT_FOUND
+	rts
+
+DUNK4:
+	stx z8c
+	sta z8b
+	ldy #2
+	bne DUNK4_3
+DUNK4_1:
+	stx z8c
+	sta z8b
+DUNK4_2:
+	ldy #4
+	lda r1H
+	sta DTrkSec+1
+	lda r1L
+	sta DTrkSec
+DUNK4_3:
+	lda z8c
+	sta DExeProc+1
+	lda z8b
+	sta DExeProc
+	lda #>DExeProc
+	sta z8c
+	lda #<DExeProc
+	sta z8b
+	jmp Hst_SendByte
+
+DUNK5:
+	ldy #1
+	jsr Hst_RecvByte
+	pha
+	tay
+	jsr Hst_RecvByte
+	pla
+	tay
+	rts
+
+__EnterTurbo:
+	lda curDrive
+	jsr SetDevice
+	ldx curDrive
+	lda _turboFlags,x
+	bmi EntTur0
+	jsr SendCODE
+	bnex EntTur5
+	ldx curDrive
+	lda #%10000000
+	sta _turboFlags,x
+EntTur0:
+	and #%01000000
+	bne EntTur3
+	jsr InitForIO
+	ldx #>EnterCommand
+	lda #<EnterCommand
+	jsr SendDOSCmd
+	bnex EntTur4
+	jsr $ffae
+:	lda cia2base+13			; wait for initial sync
+	beq :-
+	sei
+	jsr DoneWithIO
+	ldx curDrive
+	lda _turboFlags,x
+	ora #%01000000
+	sta _turboFlags,x
+EntTur3:
+	ldx #0
+	beq EntTur5
+EntTur4:
+	jsr DoneWithIO
+EntTur5:
+	rts
+
+EnterCommand:
+	.byte "M-E"
+	.word DriveStart
+
+SendExitTurbo:
+	jsr InitForIO
+	ldx #>Drv_ExitTurbo
+	lda #<Drv_ExitTurbo
+	jsr DUNK4
+	lda curDrive
+	jsr $ffb1
+	lda #$ef
+	jsr $ff93
+	jsr $ffae
+	jmp DoneWithIO
+
+SendCODE:
+	jsr InitForIO
+	lda #>DriveCode
+	sta z8e
+	lda #<DriveCode
+	sta z8d
+	lda #>DriveAddy
+	sta WriteAddy+1
+	lda #<DriveAddy
+	sta WriteAddy
+	LoadB z8f, $1a
+SndCDE0:
+	jsr SendCHUNK
+	bnex SndCDE1
+	clc
+	lda #$20
+	adc z8d
+	sta z8d
+	bcc @X
+	inc z8e
+@X:	clc
+	lda #$20
+	adc WriteAddy
+	sta WriteAddy
+	bcc @Y
+	inc WriteAddy+1
+@Y:	dec z8f
+	bpl SndCDE0
+SndCDE1:
+	jmp DoneWithIO
+
+SendCHUNK:
+	lda z8f
+	ora NUMDRV
+	beq SndCHNK1
+	ldx #>WriteCommand
+	lda #<WriteCommand
+	jsr SendDOSCmd
+	bnex SndCHNK2
+	lda #$20
+	jsr $ffa8
+	ldy #0
+SndCHNK0:
+	lda (z8d),y
+	jsr $ffa8
+	iny
+	cpy #$20
+	bcc SndCHNK0
+	jsr $ffae
+SndCHNK1:
+	ldx #0
+SndCHNK2:
+	rts
+
+WriteCommand:
+	.byte "M-W"
+WriteAddy:
+	.word 0
+
+__ExitTurbo:
+	txa
+	pha
+	ldx curDrive
+	lda _turboFlags,x
+	and #%01000000
+	beq ExiTur0
+	jsr SendExitTurbo
+	ldx curDrive
+	lda _turboFlags,x
+	and #%10111111
+	sta _turboFlags,x
+ExiTur0:
+	pla
+	tax
+	rts
+
+__PurgeTurbo:
+	jsr ClearCache
+	jsr ExitTurbo
+PurTur0:
+	ldy curDrive
+	lda #0
+	sta _turboFlags,y
+	rts
+
+__NewDisk:
+	jsr EnterTurbo
+	bnex NewDsk2
+	jsr ClearCache
+	jsr InitForIO
+	lda #0
+	sta errCount
+NewDsk0:
+	lda #>Drv_NewDisk
+	sta z8c
+	lda #<Drv_NewDisk
+	sta z8b
+	jsr DUNK4_2
+	jsr GetDOSError
+	beq NewDsk1
+	inc errCount
+	cpy errCount
+	beq NewDsk1
+	bcs NewDsk0
+NewDsk1:
+	jsr DoneWithIO
+NewDsk2:
+	rts
+
+__ChangeDiskDevice:
+	pha
+	jsr EnterTurbo
+	bnex ChngDskDv0
+	pla
+	pha
+	ora #%00100000
+	sta r1L
+	jsr InitForIO
+	ldx #>Drv_ChngDskDev
+	lda #<Drv_ChngDskDev
+	jsr DUNK4_1
+	jsr DoneWithIO
+	jsr PurTur0
+	pla
+	tax
+	lda #%11000000
+	sta _turboFlags,x
+	stx curDrive
+	stx curDevice
+	ldx #0
+	rts
+ChngDskDv0:
+	pla
+	rts
+
+__ReadBlock:
+_ReadLink:
+	jsr CheckParams_1
+	bcc RdBlock2
+	bbrf 6, curType, RdBlock0
+	jsr DoCacheRead
+	bne RdBlock2
+RdBlock0:
+	ldx #>Drv_ReadSec
+	lda #<Drv_ReadSec
+	jsr DUNK4_1
+	ldx #>Drv_SendByte
+	lda #<Drv_SendByte
+	jsr DUNK4
+	MoveW r4, z8b
+	ldy #0
+	jsr Hst_RecvByte
+	jsr GetDError
+	beqx RdBlock1
+	inc errCount
+	cpy errCount
+	beq RdBlock1
+	bcs RdBlock0
+RdBlock1:
+	bnex RdBlock2
+	bbrf 6, curType, RdBlock2
+	jsr DoCacheWrite
+	bra RdBlock2
+RdBlock2:
+	ldy #0
+	rts
+
+__WriteBlock:
+	jsr CheckParams
+	bcc WrBlock2
+WrBlock1:
+	ldx #>Drv_WriteSec
+	lda #<Drv_WriteSec
+	jsr DUNK4_1
+	MoveW r4, z8b
+	ldy #0
+	jsr Hst_SendByte
+	jsr GetDOSError
+	beq WrBlock2
+	inc errCount
+	cpy errCount
+	beq WrBlock2
+	bcs WrBlock1
+WrBlock2:
+	rts
+
+__VerWriteBlock:
+	jsr CheckParams
+	bcc VWrBlock3
+VWrBlock0:
+	lda #3
+	sta tryCount
+VWrBlock1:
+	ldx #>Drv_ReadSec
+	lda #<Drv_ReadSec
+	jsr DUNK4_1
+	jsr GetDOSError
+	beqx VWrBlock2
+	dec tryCount
+	bne VWrBlock1
+	ldx #$25
+	inc errCount
+	lda errCount
+	cmp #5
+	beq VWrBlock2
+	pha
+	jsr WriteBlock
+	pla
+	sta errCount
+	beqx VWrBlock0
+VWrBlock2:
+	bnex VWrBlock3
+	bbrf 6, curType, VWrBlock3
+	jmp DoCacheWrite
+VWrBlock3:
+	rts
+
+GetDOSError:
+	ldx #>Drv_SendByte_0
+	lda #<Drv_SendByte_0
+	jsr DUNK4
+GetDError:
+	lda #>errStore
+	sta z8c
+	lda #<errStore
+	sta z8b
+	jsr DUNK5
+	lda errStore
+	pha
+	tay
+	lda DOSErrTab-1,y
+	tay
+	pla
+	cmp #1
+	beq GetDErr1
+	addv $1e
+	bne GetDErr2
+GetDErr1:
+	lda #0
+GetDErr2:
+	tax
+	rts
+
+DOSErrTab:
+	.byte $01, $05, $02, $08
+	.byte $08, $01, $05, $01
+	.byte $05, $05, $05
+
+DriveCode:
+.segment "drv1541_drivecode"
+;		.org DriveAddy
+
+Drv_SendByte:
+	ldy #0
+	jsr Drv_SendByte_1
+Drv_SendByte_0:
+	ldy #0
+	sty $73
+	sty $74
+	iny
+	sty $71
+	ldy #0
+	lda $71
+	jsr Drv_SendByte_1
+	ldy $71
+Drv_SendByte_1:
+	LoadB $1803, $ff	; port A output
+Drv_SendByte_2:
+	dey
+	lda ($73),y
+	sta $1801		; send data
+	lda #$10
+:	bit $180d		; wait for handshake
+	beq :-
+	bit $1800		; clear flag
+	cpy #0
+	bne Drv_SendByte_2
+	LoadB $1803, $00	; port A input
+	rts
+
+Drv_RecvWord:
+	ldy #1
+	jsr Drv_RecvByte
+	sta $71
+	tay
+	jsr Drv_RecvByte
+	ldy $71
+	rts
+
+Drv_RecvByte:
+Drv_RecvByte_1:
+	lda #$10
+:	bit $180d
+	beq :-
+	bit $1800			; clear CB1
+	lda $1801			; read data
+	dey
+	sta ($73),y
+	bne Drv_RecvByte_1
+	rts
+
+D_DUNK4:
+	dec $48
+	bne D_DUNK4_1
+	jsr D_DUNK8_2
+D_DUNK4_1:
+	LoadB $1800, 0
+	rts
+
+DriveStart:
+	php
+	sei
+	PushB $49
+	LoadB $1803, $00		; port A input
+	LoadB $180c, $0b
+	lda $1801			; notify we're runing (initial sync)
+	bit $1800			; clear CB1
+	bit $180c
+	lda $180f
+	and #%11011111
+	sta $180f
+DriveLoop:
+	jsr D_DUNK8
+	LoadW $73, DExecAddy		; set rcv buffer to next command 
+	jsr Drv_RecvWord		; receive address
+	jsr D_DUNK8_1
+	LoadW $73, $0700		; buffer to data
+	lda #>(DriveLoop-1)		; return address
+	pha
+	lda #<(DriveLoop-1)
+	pha
+	jmp (DExecAddy)
+
+Drv_ExitTurbo:
+	jsr D_DUNK4_1
+	LoadB $33, 0
+	sta $1800
+	jsr $f98f			; turn drive motor off
+	LoadB $1c0c, $ec
+	pla
+	pla
+	PopB $49
+	plp
+	rts
+
+Drv_ChngDskDev:
+	lda DDatas
+	sta $77
+	eor #$60
+	sta $78
+	rts
+
+D_DUNK5:
+	jsr D_DUNK12
+	lda $22
+	beq D_DUNK5_1
+	ldx $00
+	dex
+	beq D_DUNK5_2
+D_DUNK5_1:
+	PushB $12
+	PushB $13
+	jsr Drv_NewDisk_1
+	PopB $13
+	tax
+	PopB $12
+	ldy $00
+	cpy #$01
+	bne D_DUNK5_41
+	cpx $17
+	bne D_DUNK5_5
+	cmp $16
+	bne D_DUNK5_5
+	lda #0
+D_DUNK5_2:
+	pha
+	lda $22
+	ldx #$ff
+	sec
+	sbc DDatas
+	beq D_DUNK5_4
+	bcs D_DUNK5_3
+	eor #$ff
+	adc #1
+	ldx #1
+D_DUNK5_3:
+	jsr D_DUNK6
+	lda DDatas
+	sta $22
+	jsr Drv_NewDisk_6
+D_DUNK5_4:
+	pla
+D_DUNK5_41:
+	rts
+D_DUNK5_5:
+	LoadB $00, $0b
+	rts
+
+D_DUNK6:
+	stx $4a
+	asl
+	tay
+	lda $1c00
+	and #$fe
+	sta $70
+	lda #$1e
+	sta $71
+D_DUNK6_1:
+	lda $70
+	add $4a
+	eor $70
+	and #%00000011
+	eor $70
+	sta $70
+	sta $1c00
+	lda $71
+	jsr D_DUNK6_4
+	lda $71
+	cpy #5
+	bcc D_DUNK6_2
+	cmp #$11
+	bcc D_DUNK6_3
+	sbc #2
+	bne D_DUNK6_3
+D_DUNK6_2:
+	cmp #$1c
+	bcs D_DUNK6_3
+	adc #4
+D_DUNK6_3:
+	sta $71
+	dey
+	bne D_DUNK6_1
+	lda #$4b
+D_DUNK6_4:
+	sta $1805
+	lda $1805
+	bne *-3
+	rts
+
+Drv_NewDisk:
+	jsr D_DUNK12
+Drv_NewDisk_1:
+	ldx $00
+	dex
+	beq Drv_NewDisk_2
+	ldx #$ff
+	lda #$01
+	jsr D_DUNK6
+	ldx #$01
+	txa
+	jsr D_DUNK6
+	lda #$ff
+	jsr D_DUNK6_4
+Drv_NewDisk_2:
+	LoadB $70, $04
+Drv_NewDisk_3:
+	jsr D_DUNK11
+	ldx $18
+	stx $22
+	ldy $00
+	dey
+	beq Drv_NewDisk_5
+	dec $70
+	bmi Drv_NewDisk_4
+	ldx $70
+	jsr Drv_NewDisk_7
+	sec
+	bcs Drv_NewDisk_3
+Drv_NewDisk_4:
+	LoadB $22, 0
+	rts
+Drv_NewDisk_5:
+	txa
+Drv_NewDisk_6:
+	jsr $f24b			; Establish number of sectors per track (in: A=track, out: A=number of sectors on that track)
+	sta $43
+Drv_NewDisk_7:
+	lda $1c00
+	and #$9f
+	ora DTrackTab,x
+Drv_NewDisk_8:
+	sta $1c00
+	rts
+
+D_DUNK8:			; LED off?
+	lda #$f7
+	bne D_DUNK8_3
+D_DUNK8_1:			; LED on?
+	lda #$08
+	ora $1c00
+	bne Drv_NewDisk_8
+
+D_DUNK8_2:
+	LoadB $20, 0
+	LoadB $3e, $ff
+	lda #$fb
+D_DUNK8_3:
+	and $1c00
+	jmp Drv_NewDisk_8
+
+DTrackTab:
+	.byte $00, $20, $40, $60
+
+D_DUNK9:
+	tax
+	bbrf 7, $20, D_DUNK9_0
+	jsr D_DUNK12_1
+	LoadB $20, $20
+	ldx #0
+D_DUNK9_0:
+	cpx $22
+	beq D_DUNK9_1
+	jsr Drv_NewDisk_2
+	cmp #1
+	bne D_DUNK9_1
+	ldy $19
+	iny
+	cpy $43
+	bcc @X
+	ldy #0
+@X:	sty $19
+	LoadB $45, 0
+	LoadW $32, $0018
+	jsr D_DUNK11_1
+D_DUNK9_1:
+	rts
+
+Drv_WriteSec:
+	jsr D_DUNK5
+	ldx $00
+	dex
+	bne D_DUNK10_1
+	jsr D_DUNK9
+D_DUNK10_1:
+	jsr Drv_RecvWord
+	lda #$10
+	bne D_DUNK10_2
+Drv_ReadSec:
+	jsr D_DUNK5
+	lda #0
+D_DUNK10_2:
+	ldx $00
+	dex
+	beq D_DUNK11_0
+	rts
+
+D_DUNK11:
+	lda #$30
+D_DUNK11_0:
+	sta $45
+	lda #>DDatas
+	sta $33
+	lda #<DDatas
+	sta $32
+D_DUNK11_1:
+	LoadB $31, 7
+	tsx
+	stx $49
+	ldx #1
+	stx $00
+	dex
+	stx $3f
+	LoadB $1c0c, $ee
+	lda $45
+	cmp #$10
+	beq D_DUNK11_3
+	cmp #$30
+	beq D_DUNK11_2
+	jmp $f4ca				; Test command code further ($00=read, $10=write, $20=verify, other=read block header)
+D_DUNK11_2:
+	jmp $f3b1				; Read block header, verify ID
+D_DUNK11_3:
+	jsr $f5e9				; Calculate parity for data buffer ($30)
+	sta $3a
+	lda $1c00
+	and #$10
+	bne D_DUNK11_4
+	lda #$08
+	bne D_DUNK11_9
+D_DUNK11_4:
+	jsr $f78f				; Convert 260 bytes (256+4) to 325 bytes group code buffer $01BB-$01FF and ($30)
+	jsr $f510				; Read block header (wait until needed block header arrives)
+	ldx #9
+D_DUNK11_5:
+	bvc D_DUNK11_5				; skip over sync
+	clv
+	dex
+	bne D_DUNK11_5
+	lda #$ff
+	sta $1c03
+	lda $1c0c
+	and #$1f
+	ora #$c0
+	sta $1c0c
+	lda #$ff
+	ldx #5
+	sta $1c01
+	clv
+D_DUNK11_6:
+	bvc D_DUNK11_6
+	clv
+	dex
+	bne D_DUNK11_6
+	ldy #$bb
+D_DUNK11_7:
+	lda $0100,y				; write data
+	bvc *
+	clv
+	sta $1c01
+	iny
+	bne D_DUNK11_7
+D_DUNK11_8:
+	lda ($30),y				; write data, continued
+	bvc *
+	clv
+	sta $1c01
+	iny
+	bne D_DUNK11_8
+	bvc *
+	lda $1c0c
+	ora #$e0
+	sta $1c0c
+	LoadB $1c03, 0
+	sta $50
+	lda #1
+D_DUNK11_9:
+	sta $00
+	rts
+
+D_DUNK12:					; spin up motor
+	lda $20
+	and #$20
+	bne D_DUNK12_3				; already on
+	jsr $f97e				; Turn drive motor on
+D_DUNK12_1:
+	ldy #$80				; delay until it spins up
+:	dex
+	bne :-
+	dey
+	bne :-
+	sty $3e
+D_DUNK12_3:
+	LoadB $48, $ff
+	rts
+
+DExecAddy:
+	.word 0
+DDatas:
+	;.word 0
+.segment "drv1541_b"
+
+ClrCacheDat:
+	.word 0
+
+ClearCache:
+	bbsf 6, curType, DoClearCache
+	rts
+DoClearCache:
+	LoadW r0, ClrCacheDat
+	ldy #0
+	sty r1L
+	sty r1H
+	sty r2H
+	iny
+	iny
+	sty r2L
+	iny
+	sty r3H
+	ldy curDrive
+	lda driveData,y
+	sta r3L
+DoClrCache1:
+	jsr StashRAM
+	inc r1H
+	bne DoClrCache1
+	inc r3L
+	dec r3H
+	bne DoClrCache1
+	rts
+
+DoCacheRead:
+	ldy #%10010001
+	jsr DoCacheDisk
+	ldy #0
+	lda (r4),y
+	iny
+	ora (r4),y
+	rts
+
+GiveNoError:
+	ldx #0
+	rts
+
+DoCacheVerify:
+	ldy #%10010011
+	jsr DoCacheDisk
+	and #$20
+	rts
+
+DoCacheWrite:
+	ldy #%10010000
+DoCacheDisk:
+	PushW r0
+	PushW r1
+	PushW r2
+	PushB r3L
+	tya
+	pha
+	ldy r1L
+	dey
+	lda CacheTabL,y
+	add r1H
+	sta r1H
+	lda CacheTabH,y
+	ldy curDrive
+	adc driveData,y
+	sta r3L
+	ldy #0
+	sty r1L
+	sty r2L
+	iny
+	sty r2H
+	MoveW r4, r0
+	pla
+	tay
+	jsr DoRAMOp
+	tax
+	PopB r3L
+	PopW r2
+	PopW r1
+	PopW r0
+	txa
+	ldx #0
+	rts
+
+CacheTabL:
+	.byte $00, $15, $2a, $3f, $54, $69, $7e, $93
+	.byte $a8, $bd, $d2, $e7, $fc, $11, $26, $3b
+	.byte $50, $65, $78, $8b, $9e, $b1, $c4, $d7
+	.byte $ea, $fc, $0e, $20, $32, $44, $56, $67
+	.byte $78, $89, $9a, $ab
+CacheTabH:
+	.byte $00, $00, $00, $00, $00, $00, $00, $00
+	.byte $00, $00, $00, $00, $00, $01, $01, $01
+	.byte $01, $01, $01, $01, $01, $01, $01, $01
+	.byte $01, $01, $02, $02, $02, $02, $02, $02
+	.byte $02, $02, $02, $02
+
+tmpclkreg:
+	.byte 0
+tmpPS:
+	.byte 0
+tmpgrirqen:
+	.byte 0
+tmpCPU_DATA:
+	.byte 0
+tmpmobenble:
+	.byte 0
+	.byte 0
+DExeProc:
+	.word 0
+DTrkSec:
+	.word 0
+tmpDD00:
+	.byte 0
+tmpDD00_2:
+	.byte 0
+errCount:
+	.byte 0
+errStore:
+	.byte 0
+tryCount:
+	.byte 0
+borderFlag:
+	.byte 0

From 4ca8a9e93cba313036f23b83e7b077766ea9d4de Mon Sep 17 00:00:00 2001
From: Maciej Witkowiak <ytm@elysium.pl>
Date: Sat, 23 Mar 2024 12:21:24 +0100
Subject: [PATCH 03/27] optimizations

---
 drv/drv1541parallel.s | 9 ++-------
 1 file changed, 2 insertions(+), 7 deletions(-)

diff --git a/drv/drv1541parallel.s b/drv/drv1541parallel.s
index 023dcf12..b6e92e77 100644
--- a/drv/drv1541parallel.s
+++ b/drv/drv1541parallel.s
@@ -633,13 +633,12 @@ __DoneWithIO:
 	rts
 
 Hst_RecvByte:
-Hst_RecvByte_0:
 :	lda cia2base+13		; wait for flag
 	beq :-
 	lda cia2base+1		; read data
 	dey
 	sta (z8b),y
-	bne Hst_RecvByte_0
+	bne :-
 	rts
 
 Hst_SendByte:
@@ -1034,12 +1033,8 @@ Drv_SendByte_0:
 	ldy #0
 	sty $73
 	sty $74
-	iny
-	sty $71
-	ldy #0
-	lda $71
 	jsr Drv_SendByte_1
-	ldy $71
+	ldy #1
 Drv_SendByte_1:
 	LoadB $1803, $ff	; port A output
 Drv_SendByte_2:

From 212c42b537053a21fd3fe5f4ad41c78aeb15cc86 Mon Sep 17 00:00:00 2001
From: Maciej Witkowiak <ytm@elysium.pl>
Date: Sat, 23 Mar 2024 12:50:38 +0100
Subject: [PATCH 04/27] maximum drive code size is -bash400
 (-bash300--bash6ff), calculate on the fly number of 32-byte (0) chunks needed
 to be sent via memory-write

---
 drv/drv1541parallel.cfg |  4 ++--
 drv/drv1541parallel.s   | 17 ++++++-----------
 2 files changed, 8 insertions(+), 13 deletions(-)

diff --git a/drv/drv1541parallel.cfg b/drv/drv1541parallel.cfg
index 25d05603..bc204c46 100644
--- a/drv/drv1541parallel.cfg
+++ b/drv/drv1541parallel.cfg
@@ -1,11 +1,11 @@
 MEMORY {
 	DISK_BASE:    start = $9000, size = $0D80, file = %O;
 
-	DRIVE0300:    start = $0300, size = $0500;
+	DRIVE0300:    start = $0300, size = $0400;
 }
 
 SEGMENTS {
 	drv1541:            load = DISK_BASE, type = ro;
-	drv1541_drivecode:  load = DISK_BASE, run = DRIVE0300, type = ro;
+	drv1541_drivecode:  load = DISK_BASE, run = DRIVE0300, type = ro, define = yes;
 	drv1541_b:          load = DISK_BASE, type = ro;
 }
diff --git a/drv/drv1541parallel.s b/drv/drv1541parallel.s
index b6e92e77..175d4778 100644
--- a/drv/drv1541parallel.s
+++ b/drv/drv1541parallel.s
@@ -11,9 +11,10 @@
 .include "jumptab.inc"
 .include "c64.inc"
 
-.segment "drv1541"
+.import __drv1541_drivecode_RUN__
+.import __drv1541_drivecode_SIZE__
 
-DriveAddy = $0300
+.segment "drv1541"
 
 _InitForIO:
 	.word __InitForIO
@@ -776,15 +777,9 @@ SendExitTurbo:
 
 SendCODE:
 	jsr InitForIO
-	lda #>DriveCode
-	sta z8e
-	lda #<DriveCode
-	sta z8d
-	lda #>DriveAddy
-	sta WriteAddy+1
-	lda #<DriveAddy
-	sta WriteAddy
-	LoadB z8f, $1a
+	LoadW z8d, DriveCode
+	LoadW WriteAddy, __drv1541_drivecode_RUN__
+	LoadB z8f, (<(__drv1541_drivecode_SIZE__ / $0020))
 SndCDE0:
 	jsr SendCHUNK
 	bnex SndCDE1

From 001aa8049b1127a00574d09e9b5cda69618d013a Mon Sep 17 00:00:00 2001
From: Maciej Witkowiak <ytm@elysium.pl>
Date: Sat, 23 Mar 2024 14:14:00 +0100
Subject: [PATCH 05/27] more macros and comments

---
 drv/drv1541parallel.s | 49 +++++++++++++------------------------------
 1 file changed, 14 insertions(+), 35 deletions(-)

diff --git a/drv/drv1541parallel.s b/drv/drv1541parallel.s
index 175d4778..cc6c8d1e 100644
--- a/drv/drv1541parallel.s
+++ b/drv/drv1541parallel.s
@@ -688,32 +688,23 @@ SndDOSCmd1:
 	ldx #DEV_NOT_FOUND
 	rts
 
-DUNK4:
+DUNK4:					; A/X addr of procedure to run, without parameters
 	stx z8c
 	sta z8b
-	ldy #2
+	ldy #2				; 2 bytes to send
 	bne DUNK4_3
-DUNK4_1:
+DUNK4_1:				; A/X addr of procedure to run, r1 t&s parameters
 	stx z8c
 	sta z8b
-DUNK4_2:
-	ldy #4
-	lda r1H
-	sta DTrkSec+1
-	lda r1L
-	sta DTrkSec
+DUNK4_2:				; called by NewDisk, but why send r1?
+	ldy #4				; 4 bytes to send
+	MoveW r1, DTrkSec
 DUNK4_3:
-	lda z8c
-	sta DExeProc+1
-	lda z8b
-	sta DExeProc
-	lda #>DExeProc
-	sta z8c
-	lda #<DExeProc
-	sta z8b
+	MoveW z8b, DExeProc
+	LoadW z8b, DExeProc
 	jmp Hst_SendByte
 
-DUNK5:
+DUNK5:					; receive 2 bytes, but ignorethe first(?)
 	ldy #1
 	jsr Hst_RecvByte
 	pha
@@ -859,13 +850,9 @@ __NewDisk:
 	bnex NewDsk2
 	jsr ClearCache
 	jsr InitForIO
-	lda #0
-	sta errCount
+	LoadB errCount, 0
 NewDsk0:
-	lda #>Drv_NewDisk
-	sta z8c
-	lda #<Drv_NewDisk
-	sta z8b
+	LoadW z8b, Drv_NewDisk
 	jsr DUNK4_2
 	jsr GetDOSError
 	beq NewDsk1
@@ -969,7 +956,7 @@ VWrBlock1:
 	beqx VWrBlock2
 	dec tryCount
 	bne VWrBlock1
-	ldx #$25
+	ldx #WR_VER_ERR
 	inc errCount
 	lda errCount
 	cmp #5
@@ -991,13 +978,9 @@ GetDOSError:
 	lda #<Drv_SendByte_0
 	jsr DUNK4
 GetDError:
-	lda #>errStore
-	sta z8c
-	lda #<errStore
-	sta z8b
+	LoadW z8b, errStore
 	jsr DUNK5
-	lda errStore
-	pha
+	PushB errStore
 	tay
 	lda DOSErrTab-1,y
 	tay
@@ -1528,10 +1511,6 @@ DExeProc:
 	.word 0
 DTrkSec:
 	.word 0
-tmpDD00:
-	.byte 0
-tmpDD00_2:
-	.byte 0
 errCount:
 	.byte 0
 errStore:

From d41c0e4ec4a7165eda2c30b9efd6e7625991d78d Mon Sep 17 00:00:00 2001
From: Maciej Witkowiak <ytm@elysium.pl>
Date: Sat, 23 Mar 2024 14:33:47 +0100
Subject: [PATCH 06/27] improve parallelism a bit

---
 drv/drv1541parallel.s | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drv/drv1541parallel.s b/drv/drv1541parallel.s
index cc6c8d1e..346c2e82 100644
--- a/drv/drv1541parallel.s
+++ b/drv/drv1541parallel.s
@@ -1042,8 +1042,8 @@ Drv_RecvByte_1:
 	lda #$10
 :	bit $180d
 	beq :-
-	bit $1800			; clear CB1
 	lda $1801			; read data
+	bit $1800			; clear CB1
 	dey
 	sta ($73),y
 	bne Drv_RecvByte_1

From 54cef0285a6a1b835469770530e221008733170d Mon Sep 17 00:00:00 2001
From: Maciej Witkowiak <ytm@elysium.pl>
Date: Mon, 25 Mar 2024 21:16:20 +0100
Subject: [PATCH 07/27] fix Drv_SendByte_0 to send exactly two bytes as status:
 length (1) and content (value from -bash0)

---
 drv/drv1541parallel.s | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)
 mode change 100644 => 100755 drv/drv1541parallel.s

diff --git a/drv/drv1541parallel.s b/drv/drv1541parallel.s
old mode 100644
new mode 100755
index 346c2e82..09d11024
--- a/drv/drv1541parallel.s
+++ b/drv/drv1541parallel.s
@@ -1008,11 +1008,19 @@ Drv_SendByte:
 	ldy #0
 	jsr Drv_SendByte_1
 Drv_SendByte_0:
-	ldy #0
-	sty $73
-	sty $74
-	jsr Drv_SendByte_1
-	ldy #1
+	LoadB $1803, $ff
+	LoadB $1801, $01
+	lda #$10
+:	bit $180d
+	beq :-
+	bit $1800
+	ldy $00
+	sty $1801
+:	bit $180d
+	beq :-
+	bit $1800
+	LoadB $1803, $00
+	rts
 Drv_SendByte_1:
 	LoadB $1803, $ff	; port A output
 Drv_SendByte_2:

From c9c974a9a081b7a6db185d4e3b9bf0348d10f3bf Mon Sep 17 00:00:00 2001
From: Maciej Witkowiak <ytm@elysium.pl>
Date: Mon, 25 Mar 2024 21:53:47 +0100
Subject: [PATCH 08/27] optimized drive->host transfer procedure from 35 cycles
 down to 27/28

---
 drv/drv1541parallel.s | 63 ++++++++++++++++++++++++++-----------------
 1 file changed, 39 insertions(+), 24 deletions(-)

diff --git a/drv/drv1541parallel.s b/drv/drv1541parallel.s
index 09d11024..e51c8f7a 100755
--- a/drv/drv1541parallel.s
+++ b/drv/drv1541parallel.s
@@ -634,12 +634,18 @@ __DoneWithIO:
 	rts
 
 Hst_RecvByte:
+	MoveW z8b, RecvAddr
+:	nop			; delay adjusted to Drv_SendByte timing
+	nop			; so that branch after wait for flag is mostly not taken
+	nop			; (4xNOP)=28 cycles per byte loop
+	nop
 :	lda cia2base+13		; wait for flag
 	beq :-
 	lda cia2base+1		; read data
 	dey
-	sta (z8b),y
-	bne :-
+RecvAddr = *+1
+	sta $8000,y
+	bne :--
 	rts
 
 Hst_SendByte:
@@ -1002,40 +1008,49 @@ DOSErrTab:
 
 DriveCode:
 .segment "drv1541_drivecode"
-;		.org DriveAddy
 
-Drv_SendByte:
+Drv_SendByte:			; send 256 bytes, then length (1) and status byte from $00
 	ldy #0
-	jsr Drv_SendByte_1
-Drv_SendByte_0:
-	LoadB $1803, $ff
-	LoadB $1801, $01
-	lda #$10
-:	bit $180d
-	beq :-
-	bit $1800
-	ldy $00
-	sty $1801
-:	bit $180d
-	beq :-
-	bit $1800
-	LoadB $1803, $00
-	rts
+	MoveW $73, Drv_SendAddr
 Drv_SendByte_1:
 	LoadB $1803, $ff	; port A output
-Drv_SendByte_2:
-	dey
+	dey			; first byte
 	lda ($73),y
-	sta $1801		; send data
+	sta $1801		; send first byte
+	lda #$10		; bit mask for handshake test
+Drv_SendByte_2:			; 27 cycles per byte
+	cpy #0
+	beq Drv_SendByteEnd
+	dey
+:	bit $180d		; wait for handshake
+	beq :-
+Drv_SendAddr = *+1
+	ldx $0700,y		; 1 cycle faster than lda ($73),y and we can keep A unchanged for bit test
+	stx $1801		; send data
+	bit $1800		; clear flag from previous handshake
+	jmp Drv_SendByte_2
+
+Drv_SendByteEnd:
+:	bit $180d		; wait for handshake
+	beq :-
+	bit $1800		; clear flag
+
+Drv_SendByte_0:
+	LoadB $1803, $ff	; send length (1) and status byte from $00
+	LoadB $1801, $01	; send length
 	lda #$10
 :	bit $180d		; wait for handshake
 	beq :-
 	bit $1800		; clear flag
-	cpy #0
-	bne Drv_SendByte_2
+	ldy $00
+	sty $1801		; send status
+:	bit $180d		; wait for handshake
+	beq :-
+	bit $1800		; clear flag
 	LoadB $1803, $00	; port A input
 	rts
 
+
 Drv_RecvWord:
 	ldy #1
 	jsr Drv_RecvByte

From 6e20babf7f33dbb19b867addea87a0064fd834c4 Mon Sep 17 00:00:00 2001
From: Maciej Witkowiak <ytm@elysium.pl>
Date: Mon, 25 Mar 2024 21:57:22 +0100
Subject: [PATCH 09/27] remarks and optimal interleave setting

---
 drv/drv1541parallel.s | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drv/drv1541parallel.s b/drv/drv1541parallel.s
index e51c8f7a..458e91f6 100755
--- a/drv/drv1541parallel.s
+++ b/drv/drv1541parallel.s
@@ -1,7 +1,9 @@
 ; GEOS by Berkeley Softworks
 ; reverse engineered by Maciej Witkowiak, Michael Steil
 ;
-; Commodore 1541 disk driver with parallel cable
+; Commodore 1541 disk driver with parallel cable by Maciej Witkowiak
+; NOTE: OPTIMAL_INTERLEAVE has to be determined experimentally
+; NOTE2: if drive code jams - check if 'jmp (DExecAddy)' is on page boundary - it's dangerously close
 
 .include "const.inc"
 .include "geossym.inc"
@@ -14,6 +16,9 @@
 .import __drv1541_drivecode_RUN__
 .import __drv1541_drivecode_SIZE__
 
+; we send data about 2,5 times faster, so it must be smaller than 8
+OPTIMAL_INTERLEAVE = 8
+
 .segment "drv1541"
 
 _InitForIO:
@@ -721,6 +726,7 @@ DUNK5:					; receive 2 bytes, but ignorethe first(?)
 	rts
 
 __EnterTurbo:
+	LoadB interleave, OPTIMAL_INTERLEAVE
 	lda curDrive
 	jsr SetDevice
 	ldx curDrive

From 794c87d37a9450513d798ef07ccf8334d55f126e Mon Sep 17 00:00:00 2001
From: Maciej Witkowiak <ytm@elysium.pl>
Date: Mon, 25 Mar 2024 22:55:43 +0100
Subject: [PATCH 10/27] updated with drv1541parallel mentions

---
 README.md | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/README.md b/README.md
index 6536e78f..e3fd1455 100755
--- a/README.md
+++ b/README.md
@@ -81,7 +81,7 @@ Without pucrunch/c1541, you can still build an uncompressed KERNAL binary image.
 Run `make` to build the original "BSW" GEOS for C64. This will create the following files in directory `build/bsw`:
 
 * raw KERNAL components: `kernal.bin`, `lokernal.bin`, `init.bin`
-* disk drive drivers: `drv1541.bin`, `drv1571.bin`, `drv1581.bin`
+* disk drive drivers: `drv1541.bin`, `drv1541parallel.bin`, `drv1571.bin`, `drv1581.bin`
 * input drivers: `amigamse.bin`, `joydrv.bin`, `lightpen.bin`, `mse1351.bin`, `koalapad.bin`, `pcanalog.bin`
 * combined KERNAL image (`SYS 49155`): `kernal_combined.prg`
 * compressed KERNAL image (`RUN`): `kernal_compressed.prg`
@@ -112,7 +112,7 @@ By default, the KERNAL image will contain the Commodore 1541 disk driver (`drv15
 
     make DRIVE=<drive> INPUT=<input>
 
-Supported drives are `drv1541`, `drv1571` and `drv1581`. Supported input devices are `amigamse`, `joydrv`, `koalapad`, `lightpen`, `mse1351` and `pcanalog`.
+Supported drives are `drv1541`, `drv1541parallel`, `drv1571` and `drv1581`. Supported input devices are `amigamse`, `joydrv`, `koalapad`, `lightpen`, `mse1351` and `pcanalog`.
 
 
 ## Customization

From 448e0c2a12d229ee21a48fef610ed243dc77d66c Mon Sep 17 00:00:00 2001
From: Maciej Witkowiak <ytm@elysium.pl>
Date: Sat, 30 Mar 2024 20:56:02 +0100
Subject: [PATCH 11/27] found that 6 is the optimum interleave value

---
 drv/drv1541parallel.s | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drv/drv1541parallel.s b/drv/drv1541parallel.s
index 458e91f6..c42d0e98 100755
--- a/drv/drv1541parallel.s
+++ b/drv/drv1541parallel.s
@@ -16,8 +16,7 @@
 .import __drv1541_drivecode_RUN__
 .import __drv1541_drivecode_SIZE__
 
-; we send data about 2,5 times faster, so it must be smaller than 8
-OPTIMAL_INTERLEAVE = 8
+OPTIMAL_INTERLEAVE = 6 ; 6 gives a 22% speedup
 
 .segment "drv1541"
 

From b42dc4d40707deaf6ac547d3bfaeac6b0267dd05 Mon Sep 17 00:00:00 2001
From: Maciej Witkowiak <ytm@elysium.pl>
Date: Sat, 30 Mar 2024 19:16:17 +0100
Subject: [PATCH 12/27] parallel version with otf-gcr decoding but will crash
 on write

---
 Makefile                |   4 +-
 drv/drv1541parallel.cfg |   4 +-
 drv/drv1541parallel.s   | 283 ++++++++++++++++++++++++++++++++++++++--
 3 files changed, 277 insertions(+), 14 deletions(-)

diff --git a/Makefile b/Makefile
index 6c918043..f1da873d 100644
--- a/Makefile
+++ b/Makefile
@@ -17,7 +17,7 @@ else
 D64_TEMPLATE = GEOS64.D64
 endif
 
-ASFLAGS      = -I inc -I .
+ASFLAGS      = -I inc -I . --cpu 6502X
 
 # code that is in front bank of all variants
 KERNAL_SOURCES= \
@@ -382,7 +382,7 @@ $(BUILD_DIR)/drv/drv1541.bin: $(BUILD_DIR)/drv/drv1541.o drv/drv1541.cfg $(DEPS)
 	$(LD) -C drv/drv1541.cfg $(BUILD_DIR)/drv/drv1541.o -o $@
 
 $(BUILD_DIR)/drv/drv1541parallel.bin: $(BUILD_DIR)/drv/drv1541parallel.o drv/drv1541parallel.cfg $(DEPS)
-	$(LD) -C drv/drv1541parallel.cfg $(BUILD_DIR)/drv/drv1541parallel.o -o $@
+	$(LD) -C drv/drv1541parallel.cfg -m $(BUILD_DIR)/drv/drv1541parallel.map $(BUILD_DIR)/drv/drv1541parallel.o -o $@
 
 $(BUILD_DIR)/drv/drv1571.bin: $(BUILD_DIR)/drv/drv1571.o drv/drv1571.cfg $(DEPS)
 	$(LD) -C drv/drv1571.cfg $(BUILD_DIR)/drv/drv1571.o -o $@
diff --git a/drv/drv1541parallel.cfg b/drv/drv1541parallel.cfg
index bc204c46..d24cfb28 100644
--- a/drv/drv1541parallel.cfg
+++ b/drv/drv1541parallel.cfg
@@ -1,11 +1,13 @@
 MEMORY {
 	DISK_BASE:    start = $9000, size = $0D80, file = %O;
 
-	DRIVE0300:    start = $0300, size = $0400;
+	DRIVE0300:    start = $0300, size = $0500, define = yes;
+	DRIVE0060:    start = $0086, size = $70;
 }
 
 SEGMENTS {
 	drv1541:            load = DISK_BASE, type = ro;
 	drv1541_drivecode:  load = DISK_BASE, run = DRIVE0300, type = ro, define = yes;
+	drv1541_zp:	    load = DISK_BASE, run = DRIVE0060, type = ro, define = yes;
 	drv1541_b:          load = DISK_BASE, type = ro;
 }
diff --git a/drv/drv1541parallel.s b/drv/drv1541parallel.s
index c42d0e98..016851e2 100755
--- a/drv/drv1541parallel.s
+++ b/drv/drv1541parallel.s
@@ -13,8 +13,14 @@
 .include "jumptab.inc"
 .include "c64.inc"
 
+.import __DRIVE0300_START__
+
 .import __drv1541_drivecode_RUN__
 .import __drv1541_drivecode_SIZE__
+.import __drv1541_zp_RUN__
+.import __drv1541_zp_LOAD__
+.import __drv1541_zp_SIZE__
+
 
 OPTIMAL_INTERLEAVE = 6 ; 6 gives a 22% speedup
 
@@ -745,9 +751,9 @@ EntTur0:
 	jsr SendDOSCmd
 	bnex EntTur4
 	jsr $ffae
+	sei
 :	lda cia2base+13			; wait for initial sync
 	beq :-
-	sei
 	jsr DoneWithIO
 	ldx curDrive
 	lda _turboFlags,x
@@ -780,8 +786,8 @@ SendExitTurbo:
 SendCODE:
 	jsr InitForIO
 	LoadW z8d, DriveCode
-	LoadW WriteAddy, __drv1541_drivecode_RUN__
-	LoadB z8f, (<(__drv1541_drivecode_SIZE__ / $0020))
+	LoadW WriteAddy, __DRIVE0300_START__
+	LoadB z8f, (<((__drv1541_drivecode_SIZE__) / $0020))
 SndCDE0:
 	jsr SendCHUNK
 	bnex SndCDE1
@@ -910,12 +916,15 @@ _ReadLink:
 	jsr DoCacheRead
 	bne RdBlock2
 RdBlock0:
+	ldx #>Drv_RecvZP
+	lda #<Drv_RecvZP
+	jsr DUNK4_1
+	LoadW z8b, __drv1541_zp_LOAD__
+	ldy #<(__drv1541_zp_SIZE__)
+	jsr Hst_SendByte
 	ldx #>Drv_ReadSec
 	lda #<Drv_ReadSec
 	jsr DUNK4_1
-	ldx #>Drv_SendByte
-	lda #<Drv_SendByte
-	jsr DUNK4
 	MoveW r4, z8b
 	ldy #0
 	jsr Hst_RecvByte
@@ -1014,6 +1023,13 @@ DOSErrTab:
 DriveCode:
 .segment "drv1541_drivecode"
 
+DExecAddy = $0a		; unused t&s for buffer $0500
+DDatas = DExecAddy+2		; unused t&s for buffer $0600
+
+gcrdecode:
+.byte $03, $99, $99, $99, $99, $99, $99, $99, $99, $80, $00, $10, $99, $c0, $40, $50, $99, $99, $20, $30, $99, $f0, $60, $70, $99, $90, $a0, $b0, $99, $d0, $e0, $7f, $76, $80, $99, $90, $99, $99, $99, $76, $7f, $08, $00, $01, $99, $0c, $04, $05, $99, $99, $02, $03, $99, $0f, $06, $07, $99, $09, $0a, $0b, $99, $0d, $0e, $99, $99, $00, $20, $a0, $6c, $4c, $2c, $0c, $80, $08, $08, $0c, $99, $0f, $09, $0d, $00, $00, $08, $99, $00, $99, $01, $99, $10, $01, $0c, $99, $04, $99, $05, $99, $99, $10, $30, $b0, $02, $99, $03, $99, $c0, $0c, $0f, $99, $06, $99, $07, $99, $40, $04, $09, $99, $0a, $99, $0b, $99, $50, $05, $0d, $99, $0e, $90, $00, $d0, $40, $99, $20, $e0, $60, $80, $a0, $c0, $e0, $99, $00, $04, $02, $06, $0a, $0e, $20, $02, $18, $99, $10, $99, $11, $99, $30, $03, $1c, $99, $14, $99, $15, $99, $99, $c0, $f0, $d0, $12, $99, $13, $99, $f0, $0f, $1f, $99, $16, $99, $17, $99, $60, $06, $19, $99, $1a, $99, $1b, $99, $70, $07, $1d, $99, $1e, $a4, $a4, $a4, $a3, $40, $60, $e0, $15, $13, $12, $11, $90, $09, $01, $05, $03, $07, $0b, $99, $a0, $0a, $99, $99, $99, $99, $99, $99, $b0, $0b, $99, $99, $99, $99, $99, $99, $99, $50, $70, $99, $99, $99, $99, $99, $d0, $0d, $99, $99, $99, $99, $99, $99, $e0, $0e, $99, $99, $99, $99, $99, $99, $99, $99, $99, $99, $99, $99, $99, $99
+
+
 Drv_SendByte:			; send 256 bytes, then length (1) and status byte from $00
 	ldy #0
 	MoveW $73, Drv_SendAddr
@@ -1042,6 +1058,7 @@ Drv_SendByteEnd:
 
 Drv_SendByte_0:
 	LoadB $1803, $ff	; send length (1) and status byte from $00
+Drv_SendStatus:
 	LoadB $1801, $01	; send length
 	lda #$10
 :	bit $180d		; wait for handshake
@@ -1109,6 +1126,10 @@ DriveLoop:
 	pha
 	jmp (DExecAddy)
 
+Drv_RecvZP:
+	LoadW $73, __drv1541_zp_RUN__
+	jmp Drv_RecvWord
+
 Drv_ExitTurbo:
 	jsr D_DUNK4_1
 	LoadB $33, 0
@@ -1340,7 +1361,9 @@ D_DUNK11_1:
 	stx $3f
 	LoadB $1c0c, $ee
 	lda $45
-	cmp #$10
+	bne :+
+	jmp FastReadSector
+:	cmp #$10
 	beq D_DUNK11_3
 	cmp #$30
 	beq D_DUNK11_2
@@ -1421,12 +1444,249 @@ D_DUNK12_3:
 	LoadB $48, $ff
 	rts
 
-DExecAddy:
-	.word 0
-DDatas:
-	;.word 0
+FastReadSector:
+	;;
+;	ldx #0
+;:	lda z:<__drv1541_zp_RUN__,x
+;;XXX	sta $0700,x
+;	lda FastReadZp,x
+;	sta z:<__drv1541_zp_RUN__,x
+;	inx
+;	cpx #<__drv1541_zp_SIZE__
+;	bne :-
+	;;
+	;; XXX store stack
+
+		; Encode t&s into GCR
+
+		MoveW $12, $16		; ID1,2
+		MoveW DDatas, $18	; t&s
+		lda #0
+		eor $16
+		eor $17
+		eor $18
+		eor $19
+		sta $1a			; parity
+		jsr $f934		; encode to GCR, result in $24-2b
+
+		LoadB $00, 1		; no error by default
+
+		; Wait for sync + compare encoded header (like DOS does)
+waitheader:
+		jsr $f556		; wait for sync
+		;ldy #0			; F556 sets Y to 0
+:		bvc *
+		clv
+		lda $1c01
+		cmp $24,y
+		bne waitheader		; next one
+		iny
+		cpy #8
+		bne :-			; XXX ROM does check for maximum number of tries, error would jump to sendblock below with error $02
+
+		; code from Spindle 3.1 by lft, linusakesson.net/software/spindle/
+		; Wait for a data block
+
+		ldx	#0		; will be ff when entering the loop
+		txs
+waitsync:
+		bit	$1c00
+		bpl	*-3
+
+		bit	$1c00
+		bmi	*-3
+
+		lda	$1c01	; ack the sync byte
+		clv
+		bvc	*
+		lda	$1c01	; aaaaabbb, which is 01010.010(01) for a header
+		clv		; or 01010.101(11) for data
+		eor	#$55
+		bne	waitsync
+
+		bvc	*
+		lda	$1c01	; bbcccccd
+		clv
+		.byt	$4b,$3f			; asr imm, d -> carry
+		sta	first_mod3+1
+
+		bvc	*
+		lax	$1c01			; 0 1 2 3	ddddeeee
+		.byt	$6b,$f0			; 4 5		arr imm, ddddd000
+		clv				; 6 7
+		tay				; 8 9
+first_mod3:	lda	gcrdecode		; 10 11 12 13	lsb = 000ccccc
+		ora	gcrdecode+1,y		; 14 15 16 17	y = ddddd000, lsb = 00000001
+		pha				; 18 19 20	first byte to $100
+
+		; get sector number from the lowest 5 bits of the first byte
+
+		and	#$1f			; 21 22
+		tay				; 23 24
+		nop ; lda interested,y		; 25 26
+		nop ; lda interested,y		; 27 28
+		nop ; beq notint (not taken)	; 29 30
+		;lda	interested,y		; 25 26 27 28
+;mod_safety:
+		;beq	notint			; 29 30
+
+		jmp	zpc_entry		; 31 32 33	x = ----eeee
+zp_return:
+		.byt	$6b,$f0			; arr imm, ddddd000
+		tay
+		lda	gcrdecode,x		; x = 000ccccc
+		ora	gcrdecode+1,y		; y = ddddd000, lsb = 00000001
+
+	sta $24			; checksum
+
+	; send out data, compute checksum
+	ldy #$ff
+	sty $1803		; port B output
+	iny
+	sty $25			; clear computed checksum
+:	pla
+	sta $1801		; send next byte (reversed order, as host expects)
+	eor $25
+	sta $25			; update checksum
+	lda #$10		; handshake test bit pattern
+:	bit $180d		; wait for handshake
+	beq :-
+	bit $1800		; clear CB1 flag
+	dey
+	cpy #0
+	bne :--
+
+	; compare checksum ($24==$25)
+	CmpB $24, $25
+	beq :+
+	LoadB $00, 5		; checksum error
+	; if header was found in time and checksum is OK then send status byte==1
+	; if header not found, send error $04
+:	jsr Drv_SendStatus
+
+	; restore stack
+	ldx #$45
+	txs
+
+	; restore zp
+
+;	ldx #0
+;:	lda $0700,x
+;;XXX	sta z:<__drv1541_zp_RUN__,x
+;	inx
+;	cpx #<__drv1541_zp_SIZE__
+;	bne :-
+
+	; return to main loop (XXX ExitTurbo must warm reset drive somehow)
+	jmp DriveLoop
+
+;FastReadZp:
+.segment "drv1541"
+Drv_ZPCode:
+.segment "drv1541_zp" : zeropage
+
+prof_zp:
+zpc_loop:
+		; This nop is needed for the slow bitrates (at least for 00),
+		; because apparently the third byte after a bvc sync might not be
+		; ready at cycle 65 after all.
+
+		; However, with the nop, the best case time for the entire loop
+		; is 128 cycles, which leaves too little slack for motor speed
+		; variance at bitrate 11.
+
+		; Thus, we modify the bne instruction at the end of the loop to
+		; either include or skip the nop depending on the current
+		; bitrate.
+
+		nop
+
+		lax	$1c01			; 62 63 64 65	ddddeeee
+		.byte	$6b,$f0			; 66 67		arr imm, ddddd000
+		clv				; 68 69
+		tay				; 70 71
+zpc_mod3:	lda	gcrdecode		; 72 73 74 75	lsb = 000ccccc
+		ora	gcrdecode+1,y		; 76 77 78 79	y = ddddd000, lsb = 00000001
+
+		; first read in [0..25]
+		; second read in [32..51]
+		; third read in [64..77]
+		; clv in [64..77]
+		; in total, 80 cycles from bvc
+
+		bvc	*			; 0 1
+
+		pha				; 2 3 4		second complete byte (nybbles c, d)
+zpc_entry:
+		lda	#$0f			; 5 6
+		sax	z:zpc_mod5+1		; 7 8 9
+
+		lda	$1c01			; 10 11 12 13	efffffgg
+		ldx	#$03			; 14 15
+		sax	z:zpc_mod7+1		; 16 17 18
+		.byte	$4b,$fc			; 19 20		asr imm, 0efffff0
+		tay				; 21 22
+		ldx	#$79			; 23 24
+zpc_mod5:	lda	gcrdecode,x		; 25 26 27 28	lsb = 0000eeee, x = 01111001
+		eor	gcrdecode+$40,y		; 29 30 31 32	y = 0efffff0, lsb = 01000000
+		pha				; 33 34 35	third complete byte (nybbles e, f)
+
+		lax	$1c01			; 36 37 38 39	ggghhhhh
+		clv				; 40 41
+		and	#$1f			; 42 43
+		tay				; 44 45
+
+		; first read in [0..25]
+		; second read in [32..51]
+		; clv in [32..51]
+		; in total, 46 cycles from bvc
+
+		bvc	*			; 0 1
+
+		lda	#$e0			; 2 3
+		.byte $cb, $00	; sbx	#0			; 4 5
+zpc_mod7:	lda	gcrdecode,x		; 6 7 8 9	x = ggg00000, lsb = 000000gg
+		ora	gcrdecode+$20,y		; 10 11 12 13	y = 000hhhhh, lsb = 00100000
+		pha				; 14 15 16	fourth complete byte (nybbles g, h)
+
+		; start of a new 5-byte chunk
+
+		lda	$1c01			; 17 18 19 20	aaaaabbb
+		ldx	#$f8			; 21 22
+		sax	z:zpc_mod1+1		; 23 24 25
+		and	#$07			; 26 27
+		ora	#$08			; 28 29
+		tay				; 30 31
+
+		lda	$1c01			; 32 33 34 35	bbcccccd
+		ldx	#$c0			; 36 37
+		sax	z:zpc_mod2+1		; 38 39 40
+		.byt	$4b,$3f			; 41 42		asr imm, 000ccccc, d -> carry
+		sta	z:zpc_mod3+1		; 43 44 45
+
+zpc_mod1:	lda	gcrdecode		; 46 47 48 49	lsb = aaaaa000
+zpc_mod2:	eor	gcrdecode,y		; 50 51 52 53	lsb = bb000000, y = 00001bbb
+		pha				; 54 55 56	first complete byte (nybbles a, b)
+
+		tsx				; 57 58
+BNE_WITH_NOP	=	(zpc_loop - (* + 2)) & $ff
+BNE_WITHOUT_NOP	=	(zpc_loop + 1 - (* + 2)) & $ff
+zpc_bne:	.byt	$d0,BNE_WITHOUT_NOP	; 59 60 61	bne zpc_loop
+
+		ldx	z:zpc_mod3+1		; 61 62 63
+		lda	$1c01			; 64 65 66 67	ddddeeee
+		jmp	zp_return
+
 .segment "drv1541_b"
 
+	.ifndef dontcare
+ClearCache:
+DoClearCache:
+DoCacheRead:
+DoCacheWrite:
+DoCacheVerify:
+	rts
+.else
 ClrCacheDat:
 	.word 0
 
@@ -1523,6 +1783,7 @@ CacheTabH:
 	.byte $01, $01, $01, $01, $01, $01, $01, $01
 	.byte $01, $01, $02, $02, $02, $02, $02, $02
 	.byte $02, $02, $02, $02
+.endif
 
 tmpclkreg:
 	.byte 0

From b4d92057d50934af02450095d0cc65207351de2f Mon Sep 17 00:00:00 2001
From: Maciej Witkowiak <ytm@elysium.pl>
Date: Sat, 30 Mar 2024 20:10:36 +0100
Subject: [PATCH 13/27] optimal interleave

---
 drv/drv1541parallel.s | 22 ++++++++++++++++++++--
 1 file changed, 20 insertions(+), 2 deletions(-)

diff --git a/drv/drv1541parallel.s b/drv/drv1541parallel.s
index 016851e2..8bfa2809 100755
--- a/drv/drv1541parallel.s
+++ b/drv/drv1541parallel.s
@@ -21,8 +21,26 @@
 .import __drv1541_zp_LOAD__
 .import __drv1541_zp_SIZE__
 
-
-OPTIMAL_INTERLEAVE = 6 ; 6 gives a 22% speedup
+; interleave testing in VICE (load DESK TOP saved with that interleave, count cycles between c326 and c3a8)
+; interleave	start	end	diff	diff%
+;1	124188392	138549570	14361178	226%
+;2	206544077	221469179	14925102	235%
+;3	323246805	326144363	2897558	46%
+;4	377406197	380848405	3442208	54%
+;5	444598875	448993889	4395014	69%
+;6	503908689	508692309	4783620	75%
+;7	567056391	572631055	5574664	88%
+;8	630004373	636087138	6082765	96%
+;9	717602340	724270720	6668380	105%
+;10	779826865	787041178	7214313	113%
+;11	873107683	881082247	7974564	125%
+;12	924738595	933295187	8556592	135%
+;13	1014288120	1023780169	9492049	149%
+;14	1076008138	1085921087	9912949	156%
+;15	1154807307	1165244853	10437546	164%
+
+
+OPTIMAL_INTERLEAVE = 3
 
 .segment "drv1541"
 

From 53773b7e020e7f9348a8980676d3a709616bbf9d Mon Sep 17 00:00:00 2001
From: Maciej Witkowiak <ytm@elysium.pl>
Date: Sun, 31 Mar 2024 18:32:43 +0200
Subject: [PATCH 14/27] working read/write version, buffer at 0x700 cached at
 0x200 reloaded if needed, same with ZP code

---
 drv/drv1541parallel.s | 131 +++++++++++++++++-------------------------
 1 file changed, 52 insertions(+), 79 deletions(-)

diff --git a/drv/drv1541parallel.s b/drv/drv1541parallel.s
index 8bfa2809..8207e93b 100755
--- a/drv/drv1541parallel.s
+++ b/drv/drv1541parallel.s
@@ -14,6 +14,7 @@
 .include "c64.inc"
 
 .import __DRIVE0300_START__
+.import __DRIVE0300_LAST__
 
 .import __drv1541_drivecode_RUN__
 .import __drv1541_drivecode_SIZE__
@@ -934,13 +935,16 @@ _ReadLink:
 	jsr DoCacheRead
 	bne RdBlock2
 RdBlock0:
+	lda LastOper				; need to reload ZP code?
+	beq :+					; no, it's already there
+	LoadB LastOper, 0			; mark that ZP code is loaded
 	ldx #>Drv_RecvZP
 	lda #<Drv_RecvZP
 	jsr DUNK4_1
 	LoadW z8b, __drv1541_zp_LOAD__
 	ldy #<(__drv1541_zp_SIZE__)
 	jsr Hst_SendByte
-	ldx #>Drv_ReadSec
+:	ldx #>Drv_ReadSec			; read sector and status
 	lda #<Drv_ReadSec
 	jsr DUNK4_1
 	MoveW r4, z8b
@@ -962,6 +966,7 @@ RdBlock2:
 	rts
 
 __WriteBlock:
+__VerWriteBlock:
 	jsr CheckParams
 	bcc WrBlock2
 WrBlock1:
@@ -980,37 +985,6 @@ WrBlock1:
 WrBlock2:
 	rts
 
-__VerWriteBlock:
-	jsr CheckParams
-	bcc VWrBlock3
-VWrBlock0:
-	lda #3
-	sta tryCount
-VWrBlock1:
-	ldx #>Drv_ReadSec
-	lda #<Drv_ReadSec
-	jsr DUNK4_1
-	jsr GetDOSError
-	beqx VWrBlock2
-	dec tryCount
-	bne VWrBlock1
-	ldx #WR_VER_ERR
-	inc errCount
-	lda errCount
-	cmp #5
-	beq VWrBlock2
-	pha
-	jsr WriteBlock
-	pla
-	sta errCount
-	beqx VWrBlock0
-VWrBlock2:
-	bnex VWrBlock3
-	bbrf 6, curType, VWrBlock3
-	jmp DoCacheWrite
-VWrBlock3:
-	rts
-
 GetDOSError:
 	ldx #>Drv_SendByte_0
 	lda #<Drv_SendByte_0
@@ -1043,37 +1017,12 @@ DriveCode:
 
 DExecAddy = $0a		; unused t&s for buffer $0500
 DDatas = DExecAddy+2		; unused t&s for buffer $0600
+DLastOper = $0e		; 1 if $0700-$0790 has to be restored after write
 
 gcrdecode:
 .byte $03, $99, $99, $99, $99, $99, $99, $99, $99, $80, $00, $10, $99, $c0, $40, $50, $99, $99, $20, $30, $99, $f0, $60, $70, $99, $90, $a0, $b0, $99, $d0, $e0, $7f, $76, $80, $99, $90, $99, $99, $99, $76, $7f, $08, $00, $01, $99, $0c, $04, $05, $99, $99, $02, $03, $99, $0f, $06, $07, $99, $09, $0a, $0b, $99, $0d, $0e, $99, $99, $00, $20, $a0, $6c, $4c, $2c, $0c, $80, $08, $08, $0c, $99, $0f, $09, $0d, $00, $00, $08, $99, $00, $99, $01, $99, $10, $01, $0c, $99, $04, $99, $05, $99, $99, $10, $30, $b0, $02, $99, $03, $99, $c0, $0c, $0f, $99, $06, $99, $07, $99, $40, $04, $09, $99, $0a, $99, $0b, $99, $50, $05, $0d, $99, $0e, $90, $00, $d0, $40, $99, $20, $e0, $60, $80, $a0, $c0, $e0, $99, $00, $04, $02, $06, $0a, $0e, $20, $02, $18, $99, $10, $99, $11, $99, $30, $03, $1c, $99, $14, $99, $15, $99, $99, $c0, $f0, $d0, $12, $99, $13, $99, $f0, $0f, $1f, $99, $16, $99, $17, $99, $60, $06, $19, $99, $1a, $99, $1b, $99, $70, $07, $1d, $99, $1e, $a4, $a4, $a4, $a3, $40, $60, $e0, $15, $13, $12, $11, $90, $09, $01, $05, $03, $07, $0b, $99, $a0, $0a, $99, $99, $99, $99, $99, $99, $b0, $0b, $99, $99, $99, $99, $99, $99, $99, $50, $70, $99, $99, $99, $99, $99, $d0, $0d, $99, $99, $99, $99, $99, $99, $e0, $0e, $99, $99, $99, $99, $99, $99, $99, $99, $99, $99, $99, $99, $99, $99
 
 
-Drv_SendByte:			; send 256 bytes, then length (1) and status byte from $00
-	ldy #0
-	MoveW $73, Drv_SendAddr
-Drv_SendByte_1:
-	LoadB $1803, $ff	; port A output
-	dey			; first byte
-	lda ($73),y
-	sta $1801		; send first byte
-	lda #$10		; bit mask for handshake test
-Drv_SendByte_2:			; 27 cycles per byte
-	cpy #0
-	beq Drv_SendByteEnd
-	dey
-:	bit $180d		; wait for handshake
-	beq :-
-Drv_SendAddr = *+1
-	ldx $0700,y		; 1 cycle faster than lda ($73),y and we can keep A unchanged for bit test
-	stx $1801		; send data
-	bit $1800		; clear flag from previous handshake
-	jmp Drv_SendByte_2
-
-Drv_SendByteEnd:
-:	bit $180d		; wait for handshake
-	beq :-
-	bit $1800		; clear flag
-
 Drv_SendByte_0:
 	LoadB $1803, $ff	; send length (1) and status byte from $00
 Drv_SendStatus:
@@ -1132,6 +1081,13 @@ DriveStart:
 	lda $180f
 	and #%11011111
 	sta $180f
+	ldx #0
+	stx DLastOper			; READ allowed
+:	lda $0700,x
+	sta $0200,x
+	inx
+	cpx #<(__DRIVE0300_LAST__-__DRIVE0300_START__)
+	bne :-
 DriveLoop:
 	jsr D_DUNK8
 	LoadW $73, DExecAddy		; set rcv buffer to next command 
@@ -1343,6 +1299,7 @@ D_DUNK9_1:
 	rts
 
 Drv_WriteSec:
+	LoadB DLastOper, 1		; mark that $07xx will be destroyed
 	jsr D_DUNK5
 	ldx $00
 	dex
@@ -1352,8 +1309,18 @@ D_DUNK10_1:
 	jsr Drv_RecvWord
 	lda #$10
 	bne D_DUNK10_2
+
 Drv_ReadSec:
-	jsr D_DUNK5
+	lda DLastOper			; last operation was READ?
+	beq :++
+	ldx #0				; no, restore that code after write
+	stx DLastOper
+:	lda $0200,x
+	sta $0700,x
+	inx
+	cpx #<(__DRIVE0300_LAST__-__DRIVE0300_START__)
+	bne :-
+:	jsr D_DUNK5
 	lda #0
 D_DUNK10_2:
 	ldx $00
@@ -1380,14 +1347,33 @@ D_DUNK11_1:
 	LoadB $1c0c, $ee
 	lda $45
 	bne :+
-	jmp FastReadSector
+	jmp Drv_DoReadSector
 :	cmp #$10
-	beq D_DUNK11_3
-	cmp #$30
+	bne :+
+	jmp Drv_DoWriteSector
+:	cmp #$30
 	beq D_DUNK11_2
 	jmp $f4ca				; Test command code further ($00=read, $10=write, $20=verify, other=read block header)
 D_DUNK11_2:
 	jmp $f3b1				; Read block header, verify ID
+
+D_DUNK12:					; spin up motor
+	lda $20
+	and #$20
+	bne D_DUNK12_3				; already on
+	jsr $f97e				; Turn drive motor on
+D_DUNK12_1:
+	ldy #$80				; delay until it spins up
+:	dex
+	bne :-
+	dey
+	bne :-
+	sty $3e
+D_DUNK12_3:
+	LoadB $48, $ff
+	rts
+
+Drv_DoWriteSector:
 D_DUNK11_3:
 	jsr $f5e9				; Calculate parity for data buffer ($30)
 	sta $3a
@@ -1446,23 +1432,7 @@ D_DUNK11_9:
 	sta $00
 	rts
 
-D_DUNK12:					; spin up motor
-	lda $20
-	and #$20
-	bne D_DUNK12_3				; already on
-	jsr $f97e				; Turn drive motor on
-D_DUNK12_1:
-	ldy #$80				; delay until it spins up
-:	dex
-	bne :-
-	dey
-	bne :-
-	sty $3e
-D_DUNK12_3:
-	LoadB $48, $ff
-	rts
-
-FastReadSector:
+Drv_DoReadSector:
 	;;
 ;	ldx #0
 ;:	lda z:<__drv1541_zp_RUN__,x
@@ -1826,3 +1796,6 @@ tryCount:
 	.byte 0
 borderFlag:
 	.byte 0
+LastOper:
+	.byte $ff
+

From 2c6bbaa05df7c4065c98bea8ee55fa7ae96e3130 Mon Sep 17 00:00:00 2001
From: Maciej Witkowiak <ytm@elysium.pl>
Date: Sun, 31 Mar 2024 21:05:05 +0200
Subject: [PATCH 15/27] more comments, remove dead locations and code

---
 drv/drv1541parallel.s | 60 ++++++++++++-------------------------------
 1 file changed, 17 insertions(+), 43 deletions(-)

diff --git a/drv/drv1541parallel.s b/drv/drv1541parallel.s
index 8207e93b..bf09db90 100755
--- a/drv/drv1541parallel.s
+++ b/drv/drv1541parallel.s
@@ -1083,7 +1083,7 @@ DriveStart:
 	sta $180f
 	ldx #0
 	stx DLastOper			; READ allowed
-:	lda $0700,x
+:	lda $0700,x			; cache code that would be in the write buffer zone
 	sta $0200,x
 	inx
 	cpx #<(__DRIVE0300_LAST__-__DRIVE0300_START__)
@@ -1245,10 +1245,10 @@ Drv_NewDisk_4:
 Drv_NewDisk_5:
 	txa
 Drv_NewDisk_6:
-	jsr $f24b			; Establish number of sectors per track (in: A=track, out: A=number of sectors on that track)
+	jsr $f24b			; Establish number of sectors per track (in: A=track, out: A=number of sectors on that track, X=speed zone number)
 	sta $43
 Drv_NewDisk_7:
-	lda $1c00
+	lda $1c00			; set speedzone
 	and #$9f
 	ora DTrackTab,x
 Drv_NewDisk_8:
@@ -1271,7 +1271,7 @@ D_DUNK8_3:
 	and $1c00
 	jmp Drv_NewDisk_8
 
-DTrackTab:
+DTrackTab:				; speedzone (bitrate) bits for $1c00
 	.byte $00, $20, $40, $60
 
 D_DUNK9:
@@ -1292,8 +1292,8 @@ D_DUNK9_0:
 	bcc @X
 	ldy #0
 @X:	sty $19
-	LoadB $45, 0
-	LoadW $32, $0018
+	LoadB $45, 0			; job READ
+	LoadW $32, $0018		; sector 18,0
 	jsr D_DUNK11_1
 D_DUNK9_1:
 	rts
@@ -1329,7 +1329,7 @@ D_DUNK10_2:
 	rts
 
 D_DUNK11:
-	lda #$30
+	lda #$30				; job $B0 = SEEK
 D_DUNK11_0:
 	sta $45
 	lda #>DDatas
@@ -1347,15 +1347,14 @@ D_DUNK11_1:
 	LoadB $1c0c, $ee
 	lda $45
 	bne :+
-	jmp Drv_DoReadSector
-:	cmp #$10
+	jmp Drv_DoReadSector			; job $80 = READ
+:	cmp #$10				; job $90 = WRITE
 	bne :+
 	jmp Drv_DoWriteSector
-:	cmp #$30
-	beq D_DUNK11_2
-	jmp $f4ca				; Test command code further ($00=read, $10=write, $20=verify, other=read block header)
-D_DUNK11_2:
-	jmp $f3b1				; Read block header, verify ID
+:	cmp #$30				; job $B0 = SEEK
+	beq :+
+	jmp $f4ca				; Test command code further ($00=read, $10=write, $20=verify, $30 = SEEK, is this ever used?)
+:	jmp $f3b1				; SEEK, Read block header, verify ID
 
 D_DUNK12:					; spin up motor
 	lda $20
@@ -1433,18 +1432,6 @@ D_DUNK11_9:
 	rts
 
 Drv_DoReadSector:
-	;;
-;	ldx #0
-;:	lda z:<__drv1541_zp_RUN__,x
-;;XXX	sta $0700,x
-;	lda FastReadZp,x
-;	sta z:<__drv1541_zp_RUN__,x
-;	inx
-;	cpx #<__drv1541_zp_SIZE__
-;	bne :-
-	;;
-	;; XXX store stack
-
 		; Encode t&s into GCR
 
 		MoveW $12, $16		; ID1,2
@@ -1552,25 +1539,13 @@ zp_return:
 	; if header not found, send error $04
 :	jsr Drv_SendStatus
 
-	; restore stack
+	; restore stack pointer (must be below $01bb)
 	ldx #$45
 	txs
 
-	; restore zp
-
-;	ldx #0
-;:	lda $0700,x
-;;XXX	sta z:<__drv1541_zp_RUN__,x
-;	inx
-;	cpx #<__drv1541_zp_SIZE__
-;	bne :-
-
-	; return to main loop (XXX ExitTurbo must warm reset drive somehow)
+	; return to main loop (XXX ExitTurbo must warm reset drive somehow because we have destroyed stack contents)
 	jmp DriveLoop
 
-;FastReadZp:
-.segment "drv1541"
-Drv_ZPCode:
 .segment "drv1541_zp" : zeropage
 
 prof_zp:
@@ -1667,7 +1642,8 @@ zpc_bne:	.byt	$d0,BNE_WITHOUT_NOP	; 59 60 61	bne zpc_loop
 
 .segment "drv1541_b"
 
-	.ifndef dontcare
+; there is no space for cache code and tables anymore with disk driver area, so no Shadow 1541 possible
+	.ifndef notpossible
 ClearCache:
 DoClearCache:
 DoCacheRead:
@@ -1792,8 +1768,6 @@ errCount:
 	.byte 0
 errStore:
 	.byte 0
-tryCount:
-	.byte 0
 borderFlag:
 	.byte 0
 LastOper:

From b6e303e2da75b90a894e0563d4a72eab6682bec9 Mon Sep 17 00:00:00 2001
From: Maciej Witkowiak <ytm@elysium.pl>
Date: Sun, 31 Mar 2024 21:14:11 +0200
Subject: [PATCH 16/27] faster turnaround for WriteBlock

---
 drv/drv1541parallel.s | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drv/drv1541parallel.s b/drv/drv1541parallel.s
index bf09db90..1077ceb9 100755
--- a/drv/drv1541parallel.s
+++ b/drv/drv1541parallel.s
@@ -976,7 +976,7 @@ WrBlock1:
 	MoveW r4, z8b
 	ldy #0
 	jsr Hst_SendByte
-	jsr GetDOSError
+	jsr GetDError
 	beq WrBlock2
 	inc errCount
 	cpy errCount
@@ -1429,7 +1429,7 @@ D_DUNK11_8:
 	lda #1
 D_DUNK11_9:
 	sta $00
-	rts
+	jmp Drv_SendByte_0			; set port to output, send status from $00
 
 Drv_DoReadSector:
 		; Encode t&s into GCR

From 3c0979876fefc01f38579e0c018552b133aa4216 Mon Sep 17 00:00:00 2001
From: Maciej Witkowiak <ytm@elysium.pl>
Date: Sun, 31 Mar 2024 21:26:16 +0200
Subject: [PATCH 17/27] more general memory recieve routine

---
 drv/drv1541parallel.s | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/drv/drv1541parallel.s b/drv/drv1541parallel.s
index 1077ceb9..d0997070 100755
--- a/drv/drv1541parallel.s
+++ b/drv/drv1541parallel.s
@@ -938,12 +938,15 @@ RdBlock0:
 	lda LastOper				; need to reload ZP code?
 	beq :+					; no, it's already there
 	LoadB LastOper, 0			; mark that ZP code is loaded
-	ldx #>Drv_RecvZP
+	PushW r1
+	LoadW r1, __drv1541_zp_RUN__		; target address
+	ldx #>Drv_RecvZP			; recieve data
 	lda #<Drv_RecvZP
 	jsr DUNK4_1
-	LoadW z8b, __drv1541_zp_LOAD__
-	ldy #<(__drv1541_zp_SIZE__)
+	LoadW z8b, __drv1541_zp_LOAD__		; source address
+	ldy #<(__drv1541_zp_SIZE__)		; bytes ($00=256)
 	jsr Hst_SendByte
+	PopW r1
 :	ldx #>Drv_ReadSec			; read sector and status
 	lda #<Drv_ReadSec
 	jsr DUNK4_1
@@ -1101,7 +1104,8 @@ DriveLoop:
 	jmp (DExecAddy)
 
 Drv_RecvZP:
-	LoadW $73, __drv1541_zp_RUN__
+;	LoadW $73, __drv1541_zp_RUN__
+	MoveW DDatas, $73
 	jmp Drv_RecvWord
 
 Drv_ExitTurbo:

From 66c9ff6eef26ecb3f1064e43760f84fe3f1967eb Mon Sep 17 00:00:00 2001
From: Maciej Witkowiak <ytm@elysium.pl>
Date: Sun, 31 Mar 2024 22:36:44 +0200
Subject: [PATCH 18/27] faster code upload (forced after every ExitTurbo), make
 ExitTurbo reset, we are at the size limit

---
 drv/drv1541parallel.s | 113 ++++++++++++++++++++++++++++--------------
 1 file changed, 76 insertions(+), 37 deletions(-)

diff --git a/drv/drv1541parallel.s b/drv/drv1541parallel.s
index d0997070..11b9bd56 100755
--- a/drv/drv1541parallel.s
+++ b/drv/drv1541parallel.s
@@ -757,8 +757,9 @@ __EnterTurbo:
 	lda _turboFlags,x
 	bmi EntTur0
 	jsr SendCODE
-	bnex EntTur5
-	ldx curDrive
+	beqx :+
+	jmp EntTur5
+:	ldx curDrive
 	lda #%10000000
 	sta _turboFlags,x
 EntTur0:
@@ -769,10 +770,43 @@ EntTur0:
 	lda #<EnterCommand
 	jsr SendDOSCmd
 	bnex EntTur4
+	lda cia2base+13			; clear flag
 	jsr $ffae
 	sei
 :	lda cia2base+13			; wait for initial sync
 	beq :-
+:	lda cia2base+13			; twice (some part of M-E or DriveStart setup will trigger handhsake pulse)
+	beq :-
+	lda cia2base+1			; confirm
+
+	; send remainder code for zero page
+	LoadB LastOper, $ff
+	jsr ReloadDrvZP
+
+	; fast send rest of drive code: pages $03-$07
+	LoadB EntTH+1, >DriveCode
+	LoadW r1, __DRIVE0300_START__		; target address
+EntTur1:
+	ldx #>Drv_RecvZP			; recieve data
+	lda #<Drv_RecvZP
+	jsr DUNK4_1
+	LoadB z8b, <DriveCode			; source address
+EntTH:	lda #>DriveCode
+	sta z8c
+	ldy #0
+	jsr Hst_SendByte
+	inc r1H
+	inc EntTH+1
+	CmpBI r1H, $08
+	bne EntTur1
+	; send page 7 data also to page 2
+	LoadB r1H, $02
+	ldx #>Drv_RecvZP
+	lda #<Drv_RecvZP
+	jsr DUNK4_1
+	LoadW z8b, DriveCode+$0400
+	ldy #<(__DRIVE0300_LAST__-__DRIVE0300_START__)
+	jsr Hst_SendByte
 	jsr DoneWithIO
 	ldx curDrive
 	lda _turboFlags,x
@@ -804,9 +838,9 @@ SendExitTurbo:
 
 SendCODE:
 	jsr InitForIO
-	LoadW z8d, DriveCode
-	LoadW WriteAddy, __DRIVE0300_START__
-	LoadB z8f, (<((__drv1541_drivecode_SIZE__) / $0020))
+	LoadW z8d, DriveCode+$0100	; skip over first page (gcr decode, send only 1 page of code)
+	LoadW WriteAddy, __DRIVE0300_START__+$0100
+	LoadB z8f, <($00ff/$20)
 SndCDE0:
 	jsr SendCHUNK
 	bnex SndCDE1
@@ -865,7 +899,7 @@ __ExitTurbo:
 	jsr SendExitTurbo
 	ldx curDrive
 	lda _turboFlags,x
-	and #%10111111
+	and #%00111111			; clear bit 7 because we *have to* reload the code
 	sta _turboFlags,x
 ExiTur0:
 	pla
@@ -927,14 +961,7 @@ ChngDskDv0:
 	pla
 	rts
 
-__ReadBlock:
-_ReadLink:
-	jsr CheckParams_1
-	bcc RdBlock2
-	bbrf 6, curType, RdBlock0
-	jsr DoCacheRead
-	bne RdBlock2
-RdBlock0:
+ReloadDrvZP:
 	lda LastOper				; need to reload ZP code?
 	beq :+					; no, it's already there
 	LoadB LastOper, 0			; mark that ZP code is loaded
@@ -947,7 +974,18 @@ RdBlock0:
 	ldy #<(__drv1541_zp_SIZE__)		; bytes ($00=256)
 	jsr Hst_SendByte
 	PopW r1
-:	ldx #>Drv_ReadSec			; read sector and status
+:	rts
+
+__ReadBlock:
+_ReadLink:
+	jsr CheckParams_1
+	bcc RdBlock2
+	bbrf 6, curType, RdBlock0
+	jsr DoCacheRead
+	bne RdBlock2
+RdBlock0:
+	jsr ReloadDrvZP
+	ldx #>Drv_ReadSec			; read sector and status
 	lda #<Drv_ReadSec
 	jsr DUNK4_1
 	MoveW r4, z8b
@@ -1078,24 +1116,22 @@ DriveStart:
 	PushB $49
 	LoadB $1803, $00		; port A input
 	LoadB $180c, $0b
-	lda $1801			; notify we're runing (initial sync)
-	bit $1800			; clear CB1
 	bit $180c
 	lda $180f
 	and #%11011111
 	sta $180f
-	ldx #0
-	stx DLastOper			; READ allowed
-:	lda $0700,x			; cache code that would be in the write buffer zone
-	sta $0200,x
-	inx
-	cpx #<(__DRIVE0300_LAST__-__DRIVE0300_START__)
-	bne :-
+	LoadB DLastOper,0		; READ allowed
+	bit $1800			; clear CB1
+	lda $1801			; notify we're runing (initial sync)
+	lda #$10
+:	bit $180d			; sync
+	beq :-
+	bit $1800			; clear CB1
 DriveLoop:
-	jsr D_DUNK8
+	jsr Drv_LedOFF
 	LoadW $73, DExecAddy		; set rcv buffer to next command 
 	jsr Drv_RecvWord		; receive address
-	jsr D_DUNK8_1
+	jsr Drv_LedON
 	LoadW $73, $0700		; buffer to data
 	lda #>(DriveLoop-1)		; return address
 	pha
@@ -1103,11 +1139,23 @@ DriveLoop:
 	pha
 	jmp (DExecAddy)
 
+Drv_LedOFF:
+	lda #$f7
+	and $1c00
+Drv_LedDo:
+	sta $1c00
+	rts
+Drv_LedON:
+	lda #$08
+	ora $1c00
+	bne Drv_LedDo
+
 Drv_RecvZP:
-;	LoadW $73, __drv1541_zp_RUN__
 	MoveW DDatas, $73
 	jmp Drv_RecvWord
 
+	.assert * < __DRIVE0300_START__ + $1ff, error, "Drv_Recv+DriveStart+DriveLoop+Drv_RecvZP must be within $0400-$04ff"
+
 Drv_ExitTurbo:
 	jsr D_DUNK4_1
 	LoadB $33, 0
@@ -1118,7 +1166,7 @@ Drv_ExitTurbo:
 	pla
 	PopB $49
 	plp
-	rts
+	jmp ($fffc)			; exit through reset vector
 
 Drv_ChngDskDev:
 	lda DDatas
@@ -1259,19 +1307,10 @@ Drv_NewDisk_8:
 	sta $1c00
 	rts
 
-D_DUNK8:			; LED off?
-	lda #$f7
-	bne D_DUNK8_3
-D_DUNK8_1:			; LED on?
-	lda #$08
-	ora $1c00
-	bne Drv_NewDisk_8
-
 D_DUNK8_2:
 	LoadB $20, 0
 	LoadB $3e, $ff
 	lda #$fb
-D_DUNK8_3:
 	and $1c00
 	jmp Drv_NewDisk_8
 

From e85b4f55d307405488c564d8669d664d5f7c5b0d Mon Sep 17 00:00:00 2001
From: Maciej Witkowiak <ytm@elysium.pl>
Date: Sun, 31 Mar 2024 22:52:46 +0200
Subject: [PATCH 19/27] simplify ExitTurbo (reset only), used gained space to
 check for missing block header error

---
 drv/drv1541parallel.s | 24 ++++++++++++------------
 1 file changed, 12 insertions(+), 12 deletions(-)

diff --git a/drv/drv1541parallel.s b/drv/drv1541parallel.s
index 11b9bd56..22e37641 100755
--- a/drv/drv1541parallel.s
+++ b/drv/drv1541parallel.s
@@ -1157,15 +1157,6 @@ Drv_RecvZP:
 	.assert * < __DRIVE0300_START__ + $1ff, error, "Drv_Recv+DriveStart+DriveLoop+Drv_RecvZP must be within $0400-$04ff"
 
 Drv_ExitTurbo:
-	jsr D_DUNK4_1
-	LoadB $33, 0
-	sta $1800
-	jsr $f98f			; turn drive motor off
-	LoadB $1c0c, $ec
-	pla
-	pla
-	PopB $49
-	plp
 	jmp ($fffc)			; exit through reset vector
 
 Drv_ChngDskDev:
@@ -1489,6 +1480,7 @@ Drv_DoReadSector:
 
 		LoadB $00, 1		; no error by default
 
+		ldx #90			; 90 attempts
 		; Wait for sync + compare encoded header (like DOS does)
 waitheader:
 		jsr $f556		; wait for sync
@@ -1497,11 +1489,17 @@ waitheader:
 		clv
 		lda $1c01
 		cmp $24,y
-		bne waitheader		; next one
+		bne nextheader		; next one
 		iny
 		cpy #8
 		bne :-			; XXX ROM does check for maximum number of tries, error would jump to sendblock below with error $02
+		beq foundheader
+nextheader:	dex
+		bne waitheader
+		LoadB $00, 2		; 20, 'read error'
+		jmp Drv_ReadSec_DataOut
 
+foundheader:
 		; code from Spindle 3.1 by lft, linusakesson.net/software/spindle/
 		; Wait for a data block
 
@@ -1557,6 +1555,7 @@ zp_return:
 
 	sta $24			; checksum
 
+Drv_ReadSec_DataOut:
 	; send out data, compute checksum
 	ldy #$ff
 	sty $1803		; port B output
@@ -1574,8 +1573,9 @@ zp_return:
 	cpy #0
 	bne :--
 
-	; compare checksum ($24==$25)
-	CmpB $24, $25
+	CmpBI $00, 1		; if there is error already
+	bne :+			; return it
+	CmpB $24, $25		; otherwise compare checksums
 	beq :+
 	LoadB $00, 5		; checksum error
 	; if header was found in time and checksum is OK then send status byte==1

From 0fb83439585cffb9f183e08044026abc35f85fa7 Mon Sep 17 00:00:00 2001
From: Maciej Witkowiak <ytm@elysium.pl>
Date: Tue, 2 Apr 2024 23:16:45 +0200
Subject: [PATCH 20/27] corrected Enter/Exit/PurgeTurbo to correctly handle
 each case

---
 drv/drv1541parallel.s | 43 +++++++++++++++++++++++++++----------------
 1 file changed, 27 insertions(+), 16 deletions(-)

diff --git a/drv/drv1541parallel.s b/drv/drv1541parallel.s
index 22e37641..268b30bb 100755
--- a/drv/drv1541parallel.s
+++ b/drv/drv1541parallel.s
@@ -755,17 +755,20 @@ __EnterTurbo:
 	jsr SetDevice
 	ldx curDrive
 	lda _turboFlags,x
-	bmi EntTur0
+;;	bmi EntTur0
+	bpl :+
+	jmp EntTur3
+:	jsr InitForIO
 	jsr SendCODE
 	beqx :+
-	jmp EntTur5
-:	ldx curDrive
-	lda #%10000000
-	sta _turboFlags,x
-EntTur0:
-	and #%01000000
-	bne EntTur3
-	jsr InitForIO
+	jmp EntTur4
+:;	ldx curDrive
+;	lda #%10000000
+;	sta _turboFlags,x
+;;EntTur0:
+;	and #%01000000
+;	bne EntTur3
+;	jsr InitForIO
 	ldx #>EnterCommand
 	lda #<EnterCommand
 	jsr SendDOSCmd
@@ -779,6 +782,7 @@ EntTur0:
 	beq :-
 	lda cia2base+1			; confirm
 
+;EntTur00:
 	; send remainder code for zero page
 	LoadB LastOper, $ff
 	jsr ReloadDrvZP
@@ -809,8 +813,9 @@ EntTH:	lda #>DriveCode
 	jsr Hst_SendByte
 	jsr DoneWithIO
 	ldx curDrive
-	lda _turboFlags,x
-	ora #%01000000
+;;	lda _turboFlags,x
+;;	ora #%01000000
+	lda #%11000000
 	sta _turboFlags,x
 EntTur3:
 	ldx #0
@@ -829,6 +834,8 @@ SendExitTurbo:
 	ldx #>Drv_ExitTurbo
 	lda #<Drv_ExitTurbo
 	jsr DUNK4
+:	lda cia2base+13			; wait for final sync
+	beq :-
 	lda curDrive
 	jsr $ffb1
 	lda #$ef
@@ -837,7 +844,6 @@ SendExitTurbo:
 	jmp DoneWithIO
 
 SendCODE:
-	jsr InitForIO
 	LoadW z8d, DriveCode+$0100	; skip over first page (gcr decode, send only 1 page of code)
 	LoadW WriteAddy, __DRIVE0300_START__+$0100
 	LoadB z8f, <($00ff/$20)
@@ -859,7 +865,7 @@ SndCDE0:
 @Y:	dec z8f
 	bpl SndCDE0
 SndCDE1:
-	jmp DoneWithIO
+	rts
 
 SendCHUNK:
 	lda z8f
@@ -1157,7 +1163,13 @@ Drv_RecvZP:
 	.assert * < __DRIVE0300_START__ + $1ff, error, "Drv_Recv+DriveStart+DriveLoop+Drv_RecvZP must be within $0400-$04ff"
 
 Drv_ExitTurbo:
-	jmp ($fffc)			; exit through reset vector
+	lax #0
+:	sta $00,x
+	sta $0200,x
+	inx
+	bne :-
+	bit $1801			; final sync
+	jmp $eb22			; reset routine, after RAM/ROM test
 
 Drv_ChngDskDev:
 	lda DDatas
@@ -1262,8 +1274,7 @@ Drv_NewDisk_1:
 	ldx #$ff
 	lda #$01
 	jsr D_DUNK6
-	ldx #$01
-	txa
+	lax #$01
 	jsr D_DUNK6
 	lda #$ff
 	jsr D_DUNK6_4

From c4f6f6825147d2dafd367542345a5bb7a693d463 Mon Sep 17 00:00:00 2001
From: Maciej Witkowiak <ytm@elysium.pl>
Date: Wed, 3 Apr 2024 00:03:09 +0200
Subject: [PATCH 21/27] scan for 1541s on the bus and send M-W command to set
 port A as input

---
 kernal/start/start64.s | 223 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 223 insertions(+)

diff --git a/kernal/start/start64.s b/kernal/start/start64.s
index b8725583..700e9f28 100644
--- a/kernal/start/start64.s
+++ b/kernal/start/start64.s
@@ -68,6 +68,9 @@
 ;
 
 _ResetHandle:
+.ifdef drv1541parallel
+	jsr detect_1541s
+.endif
 	sei
 	cld
 	ldx #$FF
@@ -130,6 +133,20 @@ ASSERT_NOT_BELOW_IO
 	;
 	jsr FirstInit
 	jsr MouseInit
+.ifdef drv1541parallel
+	LoadB NUMDRV, 0
+	ldy #8
+:	lda drives,y
+	cmp #DRV_1541
+	bne :+
+	sta _driveType,y
+	inc NUMDRV
+:	iny
+	cpy #12
+	bne :--
+	LoadB curType, DRV_1541
+	MoveB curDevice, curDrive
+.else
 	lda #currentInterleave
 	sta interleave
 
@@ -140,6 +157,7 @@ ASSERT_NOT_BELOW_IO
 	lda #DRV_TYPE ; see config.inc
 	sta curType
 	sta _driveType,y
+.endif
 
 ; This is the original code the cbmfiles version
 ; has at $5000.
@@ -209,3 +227,208 @@ bootSec2:
 	.byte 0
 bootOffs:
 	.byte 0
+
+.ifdef drv1541parallel
+
+; ------------------------------------------
+
+k_second	= $ff93
+k_unlstn	= $ffae
+k_listen	= $ffb1
+k_setlfs	= $ffba
+k_setnam	= $ffbd
+k_open		= $ffc0
+k_close		= $ffc3
+k_chkin		= $ffc6
+k_clrchn	= $ffcc
+k_chrin		= $ffcf
+k_chrout	= $ffd2
+k_getin		= $ffe4 
+
+drives = *-8
+	.byte 0, 0, 0, 0
+
+; multiple daisy-chained parallel port connections work with 1541 (see DualDriveBurstBackup)
+; but 1541 ROM will set port A to output upon boot ($FF10) - not clear why
+; so we have to scan for all attached 1541s and run M-W,$1803,1,0 to set port A as input
+
+detect_1541s:
+	PushB CPU_DATA
+	PushB curDevice
+ASSERT_NOT_BELOW_IO
+	LoadB CPU_DATA, KRNL_IO_IN
+	jsr drive_poll
+	; copy discovered drive types
+	ldy #8
+:	lda drives,y
+	cmp #DRV_1541
+	bne :+
+	jsr set1541PortAInput
+:	iny
+	cpy #12
+	bne :--
+	PopB curDevice
+	sta curDrive
+	PopB CPU_DATA
+	rts
+
+set1541PortAInput:
+	tya
+	pha
+	tax
+	lda #15
+	tay
+	jsr k_setlfs
+	lda #7
+	ldx #<@write1803
+	ldy #>@write1803
+	jsr k_setnam
+	jsr k_open
+	lda #15
+	jsr k_close
+	pla
+	tay
+	rts
+
+@write1803:
+	.byte "M-W"
+	.word $1803
+	.byte 1
+	.byte 0
+
+; drive detection code based on codebase64 solution https://codebase64.org/doku.php?id=base:detect_drives_on_iec_bus
+; by Todd S. Elliott
+
+drive_poll:
+
+	LoadB curDevice, 8	; start at #8
+	tay
+	lda #DRV_NULL		; that is actually 0
+:	sta drives,y		; zero out the drive buffer
+	iny
+	cpy #12
+	bne :-
+
+	; scan IEC bus, if devices exist
+@iecloop:
+	ldy #0
+	sty STATUS		; clear status
+	lda curDevice
+	jsr k_listen		; opens the device for listening
+	lda #$ff		; Secondary address - $0f OR'ed with $f0 to open
+	jsr k_second		; opens the channel with sa of 15
+
+
+	bbsf 7, STATUS, @close	; branch if there is no device present	
+
+	ldy curDevice
+	tya
+	sta drives,y		; store non-zero in successful device number
+
+@close:	jsr k_unlstn		; severs the serial bus control
+
+	LoadB STATUS, 0		; clear status
+	lda curDevice
+	jsr k_listen
+	lda #$ef		; sa - $0f and OR'ed with $e0 to close file
+	jsr k_second		; closes the channel with sa of 15
+	jsr k_unlstn		; finally closes it
+
+	inc curDevice		; next device
+	CmpBI curDevice, 12	; last device to check?
+	bne @iecloop
+
+	ldy #8
+	sty curDevice		; restart at #8
+
+@scanloop:
+	lda drives,y
+	bne @scandevice
+	iny
+	cpy #12			; are we done? (acceptable range of 8 to 30)
+	bne @scanloop
+	rts			; exits the whole drive polling routine
+
+@scandevice:
+	sty curDevice
+
+	jsr @open_cmd_channel
+	ldx #<cbminfo		; check to see if it is a 1541/1571 drive
+	ldy #>cbminfo
+	jsr @open_cmd_two
+
+	jsr k_chrin		; gets the drive info
+	cmp #'5'		; is it '5' for the 15xx drives?
+	bne @not4171
+	jsr k_chrin		; gets the next number
+	cmp #'4'		; is it '4' for the 1541?
+	bne @not41
+
+	lda #DRV_1541		; indicates a 1541 at that device number
+	bne @get_next_drive
+
+@not41:	cmp #'7'		; is it '7' for the 1571?
+	bne @not4171
+
+	lda #DRV_1571		; indicates a 1571 at that device number
+	bne @get_next_drive
+
+@not4171:			; check for 1581
+	jsr @close_cmd_channel
+	jsr @open_cmd_channel
+	ldx #<info1581		; check to see if it is a 1581 drive
+	ldy #>info1581
+	jsr @open_cmd_two
+
+	jsr k_chrin		; gets the drive info
+	cmp #'5'		; is it a '5' for a 15xx drive?
+	bne @not81
+	jsr k_chrin		; gets the next drive number
+	cmp #'8'		; is it a '8' for a 1581?
+	bne @not81
+
+	lda #DRV_1581		; indicates a 1581 at that device number
+	bne @get_next_drive
+
+@not81:	; foreign drive exists, but mark it as a missing device (no built-in drivers)
+	lda #DRV_NULL
+
+@get_next_drive:
+	ldy curDevice
+	sta drives,y
+	jsr @close_cmd_channel
+	ldy curDevice
+	iny			; increment table offset
+	jmp @scanloop
+
+@close_cmd_channel:
+	jsr k_clrchn
+	lda #15			; lfn
+	jmp k_close
+
+@open_cmd_channel:
+	lda #15			; lfn
+	tay			; sa for command channel
+	ldx curDevice
+	jsr k_setlfs		; set up the open sequence
+	lda #6			; length of command (m-r command)
+	rts
+
+@open_cmd_two:
+	jsr k_setnam		; sends the command
+	jsr k_open		; opens the file
+	ldx #15			; lfn
+	jmp k_chkin		; redirect input
+
+cbminfo:	; gets CBM drive info at $e5c5 in drive ROM
+	.byte "M-R"
+	.word $e5c5
+	.byte 2
+
+info1581:	; gets 1581 drive info at $a6e8 in drive ROM
+	.byte "M-R"
+	.word $a6e8
+	.byte 2
+
+.endif
+

From 906bf88551132e0f25ecc522c9c8a5b2b3611a2b Mon Sep 17 00:00:00 2001
From: Maciej Witkowiak <ytm@elysium.pl>
Date: Wed, 3 Apr 2024 22:14:08 +0200
Subject: [PATCH 22/27] more corrections for uploading code to drive, handle
 ReadBlock without prior NewDisk (caused by Configure)

---
 drv/drv1541parallel.s | 70 +++++++++++++++++++++++--------------------
 1 file changed, 38 insertions(+), 32 deletions(-)

diff --git a/drv/drv1541parallel.s b/drv/drv1541parallel.s
index 268b30bb..5f5e9926 100755
--- a/drv/drv1541parallel.s
+++ b/drv/drv1541parallel.s
@@ -43,6 +43,10 @@
 
 OPTIMAL_INTERLEAVE = 3
 
+DExeProc = $80
+DTrkSec  = $82
+DTrkSecH = $83
+
 .segment "drv1541"
 
 _InitForIO:
@@ -106,7 +110,7 @@ ReadBuff:
 	jmp _ReadBuff
 WriteBuff:
 	jmp _WriteBuff
-	jmp DUNK4_2
+	jmp DUNK4_1
 	jmp GetDOSError
 AllocateBlock:
 	jmp _AllocateBlock
@@ -724,18 +728,19 @@ SndDOSCmd1:
 	rts
 
 DUNK4:					; A/X addr of procedure to run, without parameters
-	stx z8c
-	sta z8b
+	stx DExeProc+1
+	sta DExeProc
 	ldy #2				; 2 bytes to send
 	bne DUNK4_3
 DUNK4_1:				; A/X addr of procedure to run, r1 t&s parameters
-	stx z8c
-	sta z8b
-DUNK4_2:				; called by NewDisk, but why send r1?
-	ldy #4				; 4 bytes to send
+	pha
 	MoveW r1, DTrkSec
+	pla
+DUNK4_11:				; A/X addr of procedure to run, parameters in DTrkSec already
+	stx DExeProc+1
+	sta DExeProc
+	ldy #4				; 4 bytes to send
 DUNK4_3:
-	MoveW z8b, DExeProc
 	LoadW z8b, DExeProc
 	jmp Hst_SendByte
 
@@ -789,25 +794,25 @@ __EnterTurbo:
 
 	; fast send rest of drive code: pages $03-$07
 	LoadB EntTH+1, >DriveCode
-	LoadW r1, __DRIVE0300_START__		; target address
+	LoadW DTrkSec, __DRIVE0300_START__	; target address
 EntTur1:
 	ldx #>Drv_RecvZP			; recieve data
 	lda #<Drv_RecvZP
-	jsr DUNK4_1
+	jsr DUNK4_11
 	LoadB z8b, <DriveCode			; source address
 EntTH:	lda #>DriveCode
 	sta z8c
 	ldy #0
 	jsr Hst_SendByte
-	inc r1H
+	inc DTrkSecH
 	inc EntTH+1
-	CmpBI r1H, $08
+	CmpBI DTrkSecH, $08
 	bne EntTur1
 	; send page 7 data also to page 2
-	LoadB r1H, $02
+	LoadB DTrkSecH, $02
 	ldx #>Drv_RecvZP
 	lda #<Drv_RecvZP
-	jsr DUNK4_1
+	jsr DUNK4_11
 	LoadW z8b, DriveCode+$0400
 	ldy #<(__DRIVE0300_LAST__-__DRIVE0300_START__)
 	jsr Hst_SendByte
@@ -928,8 +933,9 @@ __NewDisk:
 	jsr InitForIO
 	LoadB errCount, 0
 NewDsk0:
-	LoadW z8b, Drv_NewDisk
-	jsr DUNK4_2
+	ldx #>Drv_NewDisk
+	lda #<Drv_NewDisk
+	jsr DUNK4_1
 	jsr GetDOSError
 	beq NewDsk1
 	inc errCount
@@ -971,15 +977,13 @@ ReloadDrvZP:
 	lda LastOper				; need to reload ZP code?
 	beq :+					; no, it's already there
 	LoadB LastOper, 0			; mark that ZP code is loaded
-	PushW r1
-	LoadW r1, __drv1541_zp_RUN__		; target address
+	LoadW DTrkSec, __drv1541_zp_RUN__	; target address
 	ldx #>Drv_RecvZP			; recieve data
 	lda #<Drv_RecvZP
-	jsr DUNK4_1
+	jsr DUNK4_11
 	LoadW z8b, __drv1541_zp_LOAD__		; source address
 	ldy #<(__drv1541_zp_SIZE__)		; bytes ($00=256)
 	jsr Hst_SendByte
-	PopW r1
 :	rts
 
 __ReadBlock:
@@ -1186,20 +1190,27 @@ D_DUNK5:
 	dex
 	beq D_DUNK5_2
 D_DUNK5_1:
-	PushB $12
+	lda $12				; was disk logged in?
+	ora $13
+	beq :+				; no, just read the ID
+
+	PushB $12			; preserve current disk ID
 	PushB $13
 	jsr Drv_NewDisk_1
 	PopB $13
 	tax
 	PopB $12
 	ldy $00
-	cpy #$01
-	bne D_DUNK5_41
-	cpx $17
-	bne D_DUNK5_5
+	cpy #$01			; any error?
+	bne D_DUNK5_41			; yes, error
+	cpx $17				; different ID?
+	bne D_DUNK5_5			; yes, error
 	cmp $16
 	bne D_DUNK5_5
-	lda #0
+	beq :++
+
+:	jsr Drv_NewDisk_1		; login disk
+:	lda #0				; ID the same
 D_DUNK5_2:
 	pha
 	lda $22
@@ -1221,7 +1232,7 @@ D_DUNK5_4:
 D_DUNK5_41:
 	rts
 D_DUNK5_5:
-	LoadB $00, $0b
+	LoadB $00, $0b			; ID mismatch
 	rts
 
 D_DUNK6:
@@ -1813,11 +1824,6 @@ tmpCPU_DATA:
 	.byte 0
 tmpmobenble:
 	.byte 0
-	.byte 0
-DExeProc:
-	.word 0
-DTrkSec:
-	.word 0
 errCount:
 	.byte 0
 errStore:

From 7049903729c2f9f398e16f3152fc1936da79fd9b Mon Sep 17 00:00:00 2001
From: Maciej Witkowiak <ytm@elysium.pl>
Date: Wed, 3 Apr 2024 22:32:02 +0200
Subject: [PATCH 23/27] remove all code related to disk cache, no space for
 that

---
 drv/drv1541parallel.s | 136 +-----------------------------------------
 1 file changed, 2 insertions(+), 134 deletions(-)

diff --git a/drv/drv1541parallel.s b/drv/drv1541parallel.s
index 5f5e9926..f0611b4c 100755
--- a/drv/drv1541parallel.s
+++ b/drv/drv1541parallel.s
@@ -156,9 +156,6 @@ SetDirHead:
 	rts
 
 CheckParams:
-	bbrf 6, curType, CheckParams_1
-	jsr DoCacheVerify
-	beq CheckParams_2
 CheckParams_1:
 	lda #0
 	sta errCount
@@ -183,12 +180,7 @@ __OpenDisk:
 	bnex OpenDsk1
 	jsr GetDirHead
 	bnex OpenDsk1
-	bbrf 6, tmpDriveType, OpenDsk0
-	jsr DoCacheVerify
-	beq OpenDsk0
-	jsr DoClearCache
 	jsr SetDirHead
-	jsr DoCacheWrite
 OpenDsk0:
 	LoadW r5, curDirHead
 	jsr ChkDkGEOS
@@ -760,21 +752,13 @@ __EnterTurbo:
 	jsr SetDevice
 	ldx curDrive
 	lda _turboFlags,x
-;;	bmi EntTur0
 	bpl :+
 	jmp EntTur3
 :	jsr InitForIO
 	jsr SendCODE
 	beqx :+
 	jmp EntTur4
-:;	ldx curDrive
-;	lda #%10000000
-;	sta _turboFlags,x
-;;EntTur0:
-;	and #%01000000
-;	bne EntTur3
-;	jsr InitForIO
-	ldx #>EnterCommand
+:	ldx #>EnterCommand
 	lda #<EnterCommand
 	jsr SendDOSCmd
 	bnex EntTur4
@@ -787,7 +771,6 @@ __EnterTurbo:
 	beq :-
 	lda cia2base+1			; confirm
 
-;EntTur00:
 	; send remainder code for zero page
 	LoadB LastOper, $ff
 	jsr ReloadDrvZP
@@ -918,7 +901,6 @@ ExiTur0:
 	rts
 
 __PurgeTurbo:
-	jsr ClearCache
 	jsr ExitTurbo
 PurTur0:
 	ldy curDrive
@@ -929,7 +911,6 @@ PurTur0:
 __NewDisk:
 	jsr EnterTurbo
 	bnex NewDsk2
-	jsr ClearCache
 	jsr InitForIO
 	LoadB errCount, 0
 NewDsk0:
@@ -990,9 +971,6 @@ __ReadBlock:
 _ReadLink:
 	jsr CheckParams_1
 	bcc RdBlock2
-	bbrf 6, curType, RdBlock0
-	jsr DoCacheRead
-	bne RdBlock2
 RdBlock0:
 	jsr ReloadDrvZP
 	ldx #>Drv_ReadSec			; read sector and status
@@ -1002,16 +980,13 @@ RdBlock0:
 	ldy #0
 	jsr Hst_RecvByte
 	jsr GetDError
-	beqx RdBlock1
+	beq RdBlock1
 	inc errCount
 	cpy errCount
 	beq RdBlock1
 	bcs RdBlock0
 RdBlock1:
 	bnex RdBlock2
-	bbrf 6, curType, RdBlock2
-	jsr DoCacheWrite
-	bra RdBlock2
 RdBlock2:
 	ldy #0
 	rts
@@ -1707,113 +1682,6 @@ zpc_bne:	.byt	$d0,BNE_WITHOUT_NOP	; 59 60 61	bne zpc_loop
 
 .segment "drv1541_b"
 
-; there is no space for cache code and tables anymore with disk driver area, so no Shadow 1541 possible
-	.ifndef notpossible
-ClearCache:
-DoClearCache:
-DoCacheRead:
-DoCacheWrite:
-DoCacheVerify:
-	rts
-.else
-ClrCacheDat:
-	.word 0
-
-ClearCache:
-	bbsf 6, curType, DoClearCache
-	rts
-DoClearCache:
-	LoadW r0, ClrCacheDat
-	ldy #0
-	sty r1L
-	sty r1H
-	sty r2H
-	iny
-	iny
-	sty r2L
-	iny
-	sty r3H
-	ldy curDrive
-	lda driveData,y
-	sta r3L
-DoClrCache1:
-	jsr StashRAM
-	inc r1H
-	bne DoClrCache1
-	inc r3L
-	dec r3H
-	bne DoClrCache1
-	rts
-
-DoCacheRead:
-	ldy #%10010001
-	jsr DoCacheDisk
-	ldy #0
-	lda (r4),y
-	iny
-	ora (r4),y
-	rts
-
-GiveNoError:
-	ldx #0
-	rts
-
-DoCacheVerify:
-	ldy #%10010011
-	jsr DoCacheDisk
-	and #$20
-	rts
-
-DoCacheWrite:
-	ldy #%10010000
-DoCacheDisk:
-	PushW r0
-	PushW r1
-	PushW r2
-	PushB r3L
-	tya
-	pha
-	ldy r1L
-	dey
-	lda CacheTabL,y
-	add r1H
-	sta r1H
-	lda CacheTabH,y
-	ldy curDrive
-	adc driveData,y
-	sta r3L
-	ldy #0
-	sty r1L
-	sty r2L
-	iny
-	sty r2H
-	MoveW r4, r0
-	pla
-	tay
-	jsr DoRAMOp
-	tax
-	PopB r3L
-	PopW r2
-	PopW r1
-	PopW r0
-	txa
-	ldx #0
-	rts
-
-CacheTabL:
-	.byte $00, $15, $2a, $3f, $54, $69, $7e, $93
-	.byte $a8, $bd, $d2, $e7, $fc, $11, $26, $3b
-	.byte $50, $65, $78, $8b, $9e, $b1, $c4, $d7
-	.byte $ea, $fc, $0e, $20, $32, $44, $56, $67
-	.byte $78, $89, $9a, $ab
-CacheTabH:
-	.byte $00, $00, $00, $00, $00, $00, $00, $00
-	.byte $00, $00, $00, $00, $00, $01, $01, $01
-	.byte $01, $01, $01, $01, $01, $01, $01, $01
-	.byte $01, $01, $02, $02, $02, $02, $02, $02
-	.byte $02, $02, $02, $02
-.endif
-
 tmpclkreg:
 	.byte 0
 tmpPS:

From 8782f756dd3199c25979f2db9fc939afed8d8119 Mon Sep 17 00:00:00 2001
From: Maciej Witkowiak <ytm@elysium.pl>
Date: Wed, 3 Apr 2024 23:03:17 +0200
Subject: [PATCH 24/27] correct ExitTurbo to preserve device number

---
 drv/drv1541parallel.s | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/drv/drv1541parallel.s b/drv/drv1541parallel.s
index f0611b4c..329bc0d1 100755
--- a/drv/drv1541parallel.s
+++ b/drv/drv1541parallel.s
@@ -1142,13 +1142,22 @@ Drv_RecvZP:
 	.assert * < __DRIVE0300_START__ + $1ff, error, "Drv_Recv+DriveStart+DriveLoop+Drv_RecvZP must be within $0400-$04ff"
 
 Drv_ExitTurbo:
+	jsr Drv_LedOFF
+	ldy $78				; preserve device number
 	lax #0
 :	sta $00,x
 	sta $0200,x
 	inx
 	bne :-
 	bit $1801			; final sync
-	jmp $eb22			; reset routine, after RAM/ROM test
+	LoadB $180c, $01		; CA1 (ATN IN) trigger on positive edge
+	lda #$82
+	sta $180d			; interrupt possible through ATN IN
+	sta $180e
+	ldx #$45
+	txs
+	tya				; restore device number ($78)
+	jmp $eb45			; reset routine, after RAM/ROM test when device number is set
 
 Drv_ChngDskDev:
 	lda DDatas

From a4113b9147e3e42fea1ad84401f019e397c9bd58 Mon Sep 17 00:00:00 2001
From: Maciej Witkowiak <ytm@elysium.pl>
Date: Wed, 3 Apr 2024 23:24:37 +0200
Subject: [PATCH 25/27] don't send page 07xx twice, move ExitTurbo to the end
 to fit whole WriteSector under 0x700

---
 drv/drv1541parallel.s | 52 ++++++++++++++++++++++++++-----------------
 1 file changed, 32 insertions(+), 20 deletions(-)

diff --git a/drv/drv1541parallel.s b/drv/drv1541parallel.s
index 329bc0d1..b013a3f5 100755
--- a/drv/drv1541parallel.s
+++ b/drv/drv1541parallel.s
@@ -789,9 +789,10 @@ EntTH:	lda #>DriveCode
 	jsr Hst_SendByte
 	inc DTrkSecH
 	inc EntTH+1
-	CmpBI DTrkSecH, $08
+	CmpBI DTrkSecH, $07
 	bne EntTur1
 	; send page 7 data also to page 2
+	inc z8c
 	LoadB DTrkSecH, $02
 	ldx #>Drv_RecvZP
 	lda #<Drv_RecvZP
@@ -1105,10 +1106,10 @@ DriveStart:
 	lda $180f
 	and #%11011111
 	sta $180f
-	LoadB DLastOper,0		; READ allowed
 	bit $1800			; clear CB1
 	lda $1801			; notify we're runing (initial sync)
 	lda #$10
+	sta DLastOper			; READ not allowed
 :	bit $180d			; sync
 	beq :-
 	bit $1800			; clear CB1
@@ -1142,22 +1143,8 @@ Drv_RecvZP:
 	.assert * < __DRIVE0300_START__ + $1ff, error, "Drv_Recv+DriveStart+DriveLoop+Drv_RecvZP must be within $0400-$04ff"
 
 Drv_ExitTurbo:
-	jsr Drv_LedOFF
-	ldy $78				; preserve device number
-	lax #0
-:	sta $00,x
-	sta $0200,x
-	inx
-	bne :-
-	bit $1801			; final sync
-	LoadB $180c, $01		; CA1 (ATN IN) trigger on positive edge
-	lda #$82
-	sta $180d			; interrupt possible through ATN IN
-	sta $180e
-	ldx #$45
-	txs
-	tya				; restore device number ($78)
-	jmp $eb45			; reset routine, after RAM/ROM test when device number is set
+	jsr Drv_RestorePage7
+	jmp Drv_DoExitTurbo
 
 Drv_ChngDskDev:
 	lda DDatas
@@ -1350,7 +1337,7 @@ D_DUNK10_1:
 	lda #$10
 	bne D_DUNK10_2
 
-Drv_ReadSec:
+Drv_RestorePage7:
 	lda DLastOper			; last operation was READ?
 	beq :++
 	ldx #0				; no, restore that code after write
@@ -1360,7 +1347,11 @@ Drv_ReadSec:
 	inx
 	cpx #<(__DRIVE0300_LAST__-__DRIVE0300_START__)
 	bne :-
-:	jsr D_DUNK5
+:	rts
+
+Drv_ReadSec:
+	jsr Drv_RestorePage7
+	jsr D_DUNK5
 	lda #0
 D_DUNK10_2:
 	ldx $00
@@ -1471,6 +1462,8 @@ D_DUNK11_9:
 	sta $00
 	jmp Drv_SendByte_0			; set port to output, send status from $00
 
+	.assert * < $700, error, "D_DUNK11 (WriteSector) must end before $0700"
+
 Drv_DoReadSector:
 		; Encode t&s into GCR
 
@@ -1595,6 +1588,25 @@ Drv_ReadSec_DataOut:
 	; return to main loop (XXX ExitTurbo must warm reset drive somehow because we have destroyed stack contents)
 	jmp DriveLoop
 
+Drv_DoExitTurbo:
+	jsr Drv_LedOFF
+	ldy $78				; preserve device number
+	lax #0
+:	sta $00,x
+	sta $0200,x
+	inx
+	bne :-
+	bit $1801			; final sync
+	LoadB $180c, $01		; CA1 (ATN IN) trigger on positive edge
+	lda #$82
+	sta $180d			; interrupt possible through ATN IN
+	sta $180e
+	ldx #$45
+	txs
+	tya				; restore device number ($78)
+	jmp $eb45			; reset routine, after RAM/ROM test when device number is set
+
+
 .segment "drv1541_zp" : zeropage
 
 prof_zp:

From 1cdef914c494ae1e6bd323350828d77ab9f4fa68 Mon Sep 17 00:00:00 2001
From: Maciej Witkowiak <ytm@elysium.pl>
Date: Thu, 4 Apr 2024 21:20:28 +0200
Subject: [PATCH 26/27] reorder drivecode to send fewer bytes via slow M-W

---
 drv/drv1541parallel.s | 62 ++++++++++++++++++++-----------------------
 1 file changed, 29 insertions(+), 33 deletions(-)

diff --git a/drv/drv1541parallel.s b/drv/drv1541parallel.s
index b013a3f5..c8b9f9b4 100755
--- a/drv/drv1541parallel.s
+++ b/drv/drv1541parallel.s
@@ -789,10 +789,9 @@ EntTH:	lda #>DriveCode
 	jsr Hst_SendByte
 	inc DTrkSecH
 	inc EntTH+1
-	CmpBI DTrkSecH, $07
+	CmpBI DTrkSecH, >(__DRIVE0300_LAST__)
 	bne EntTur1
-	; send page 7 data also to page 2
-	inc z8c
+	; send page 7 data to page 2
 	LoadB DTrkSecH, $02
 	ldx #>Drv_RecvZP
 	lda #<Drv_RecvZP
@@ -802,8 +801,6 @@ EntTH:	lda #>DriveCode
 	jsr Hst_SendByte
 	jsr DoneWithIO
 	ldx curDrive
-;;	lda _turboFlags,x
-;;	ora #%01000000
 	lda #%11000000
 	sta _turboFlags,x
 EntTur3:
@@ -835,7 +832,7 @@ SendExitTurbo:
 SendCODE:
 	LoadW z8d, DriveCode+$0100	; skip over first page (gcr decode, send only 1 page of code)
 	LoadW WriteAddy, __DRIVE0300_START__+$0100
-	LoadB z8f, <($00ff/$20)
+	LoadB z8f, <( (Drv_END_MW_CODE-__DRIVE0300_START__-$0100) / $0020)
 SndCDE0:
 	jsr SendCHUNK
 	bnex SndCDE1
@@ -1049,24 +1046,6 @@ DLastOper = $0e		; 1 if $0700-$0790 has to be restored after write
 gcrdecode:
 .byte $03, $99, $99, $99, $99, $99, $99, $99, $99, $80, $00, $10, $99, $c0, $40, $50, $99, $99, $20, $30, $99, $f0, $60, $70, $99, $90, $a0, $b0, $99, $d0, $e0, $7f, $76, $80, $99, $90, $99, $99, $99, $76, $7f, $08, $00, $01, $99, $0c, $04, $05, $99, $99, $02, $03, $99, $0f, $06, $07, $99, $09, $0a, $0b, $99, $0d, $0e, $99, $99, $00, $20, $a0, $6c, $4c, $2c, $0c, $80, $08, $08, $0c, $99, $0f, $09, $0d, $00, $00, $08, $99, $00, $99, $01, $99, $10, $01, $0c, $99, $04, $99, $05, $99, $99, $10, $30, $b0, $02, $99, $03, $99, $c0, $0c, $0f, $99, $06, $99, $07, $99, $40, $04, $09, $99, $0a, $99, $0b, $99, $50, $05, $0d, $99, $0e, $90, $00, $d0, $40, $99, $20, $e0, $60, $80, $a0, $c0, $e0, $99, $00, $04, $02, $06, $0a, $0e, $20, $02, $18, $99, $10, $99, $11, $99, $30, $03, $1c, $99, $14, $99, $15, $99, $99, $c0, $f0, $d0, $12, $99, $13, $99, $f0, $0f, $1f, $99, $16, $99, $17, $99, $60, $06, $19, $99, $1a, $99, $1b, $99, $70, $07, $1d, $99, $1e, $a4, $a4, $a4, $a3, $40, $60, $e0, $15, $13, $12, $11, $90, $09, $01, $05, $03, $07, $0b, $99, $a0, $0a, $99, $99, $99, $99, $99, $99, $b0, $0b, $99, $99, $99, $99, $99, $99, $99, $50, $70, $99, $99, $99, $99, $99, $d0, $0d, $99, $99, $99, $99, $99, $99, $e0, $0e, $99, $99, $99, $99, $99, $99, $99, $99, $99, $99, $99, $99, $99, $99
 
-
-Drv_SendByte_0:
-	LoadB $1803, $ff	; send length (1) and status byte from $00
-Drv_SendStatus:
-	LoadB $1801, $01	; send length
-	lda #$10
-:	bit $180d		; wait for handshake
-	beq :-
-	bit $1800		; clear flag
-	ldy $00
-	sty $1801		; send status
-:	bit $180d		; wait for handshake
-	beq :-
-	bit $1800		; clear flag
-	LoadB $1803, $00	; port A input
-	rts
-
-
 Drv_RecvWord:
 	ldy #1
 	jsr Drv_RecvByte
@@ -1088,14 +1067,6 @@ Drv_RecvByte_1:
 	bne Drv_RecvByte_1
 	rts
 
-D_DUNK4:
-	dec $48
-	bne D_DUNK4_1
-	jsr D_DUNK8_2
-D_DUNK4_1:
-	LoadB $1800, 0
-	rts
-
 DriveStart:
 	php
 	sei
@@ -1140,7 +1111,24 @@ Drv_RecvZP:
 	MoveW DDatas, $73
 	jmp Drv_RecvWord
 
-	.assert * < __DRIVE0300_START__ + $1ff, error, "Drv_Recv+DriveStart+DriveLoop+Drv_RecvZP must be within $0400-$04ff"
+Drv_END_MW_CODE:		; marker for end of code that has to be sent via M-W command
+
+Drv_SendByte_0:
+	LoadB $1803, $ff	; send length (1) and status byte from $00
+Drv_SendStatus:
+	LoadB $1801, $01	; send length
+	lda #$10
+:	bit $180d		; wait for handshake
+	beq :-
+	bit $1800		; clear flag
+	ldy $00
+	sty $1801		; send status
+:	bit $180d		; wait for handshake
+	beq :-
+	bit $1800		; clear flag
+	LoadB $1803, $00	; port A input
+	rts
+
 
 Drv_ExitTurbo:
 	jsr Drv_RestorePage7
@@ -1153,6 +1141,14 @@ Drv_ChngDskDev:
 	sta $78
 	rts
 
+D_DUNK4:
+	dec $48
+	bne D_DUNK4_1
+	jsr D_DUNK8_2
+D_DUNK4_1:
+	LoadB $1800, 0
+	rts
+
 D_DUNK5:
 	jsr D_DUNK12
 	lda $22

From 9bc60289fc345dbab09ada506c7abc6cf2e24039 Mon Sep 17 00:00:00 2001
From: Maciej Witkowiak <ytm@elysium.pl>
Date: Thu, 4 Apr 2024 21:49:34 +0200
Subject: [PATCH 27/27] docs

---
 drv/drv1541parallel.s | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drv/drv1541parallel.s b/drv/drv1541parallel.s
index c8b9f9b4..66adeb2c 100755
--- a/drv/drv1541parallel.s
+++ b/drv/drv1541parallel.s
@@ -1,9 +1,9 @@
 ; GEOS by Berkeley Softworks
 ; reverse engineered by Maciej Witkowiak, Michael Steil
 ;
+; On the fly sector read and GCR decoding code from Spindle 3.1 by lft, linusakesson.net/software/spindle/
+;
 ; Commodore 1541 disk driver with parallel cable by Maciej Witkowiak
-; NOTE: OPTIMAL_INTERLEAVE has to be determined experimentally
-; NOTE2: if drive code jams - check if 'jmp (DExecAddy)' is on page boundary - it's dangerously close
 
 .include "const.inc"
 .include "geossym.inc"