Merge pull request #244 from davidgiven/c64

Add a fastloader for the C64 and VIC20 ports.

Author: davidgiven

.github/workflows/ccpp.yml

@@ -11,7 +11,7 @@ jobs:
         repository: 'davidgiven/cpm65'
 
     - name: apt
-      run: sudo apt update && sudo apt install cc1541 cpmtools libfmt-dev fp-compiler moreutils mame srecord 64tass libreadline-dev
+      run: sudo apt update && sudo apt install cc1541 cpmtools libfmt-dev fp-compiler moreutils mame srecord 64tass libreadline-dev libelf-dev
 
     - name: install llvm-mos
       run: |

.github/workflows/release.yml

@@ -15,7 +15,7 @@ jobs:
         path: 'cpm65'
 
     - name: apt
-      run: sudo apt update && sudo apt install cc1541 cpmtools libfmt-dev fp-compiler moreutils srecord 64tass libreadline-dev
+      run: sudo apt update && sudo apt install cc1541 cpmtools libfmt-dev fp-compiler moreutils srecord 64tass libreadline-dev libelf-dev
 
     - name: install llvm-mos
       run: |

README.md

@@ -163,17 +163,20 @@ the same time.
 
   - Load and run the `CPM` program to start.
 
-  - It's excruciatingly slow as it uses normal 1541 disk accesses at 300 bytes
-	  per second. Everything works, but you won't enjoy it. At some point I want
-	  to add a fastloader.
+  - It has its own built-in fastloader, which has been lightly tested but seems
+    to work on both NTSC and PAL C64s. It needs tuning but currently seems to get
+    about 1100 bytes per second, which is 4x the normal 1541 speed. (It's the same
+    one as for the VIC-20.)
 
   - The disk image produced is a hybrid of a CP/M file system and a CBMDOS file
 	  system, which can be accessed as either. The disk structures used by the
 	  other file system are hidden. You get about 170kB on a normal disk.
 
-  - Disk accesses are done using direct block access, so it _won't_ work on
-	  anything other than a 1541 (but it should be straightforward to add
-	  support for other drives). Sorry.
+  - It'll only work on a 1541, and probably only a 1541-II. Because of the
+    fastloader. Sorry. Porting it to other drives is perfectly possible, I
+    just haven't done it.
+
+  - This won't work on MAME. You'll need VICE to emulate it.
 
 ### VIC-20 notes
 
@@ -186,9 +189,6 @@ the same time.
     doesn't look great but is surprisingly readable, and is vastly better than
     the VIC-20's default 22x24 screen mode.
 
-  - Disk accesses are slightly faster than the Commodore 64, but only just.
-    It's still a miserable experience.
-
 ### Commodore PET notes
 
   - You need a PET 4032, 8032 or 8096 and either a 4040 disk drive or something

build.py

@@ -3,6 +3,7 @@
 
 package(name="libreadline", package="readline")
 package(name="libfmt", package="fmt")
+package(name="libelf", package="libelf")
 
 export(
     name="all",
@@ -63,18 +64,28 @@
     name="mametest",
     deps=[
         "src/arch/bbcmicro+mametest",
-        "src/arch/commodore+c64_mametest",
+        
+        # Isn't accurate enough to support the fastloader.
+        #"src/arch/commodore+c64_mametest",
+        
+        # As above, and also doesn't support enough memory expansions.
+        #"src/arch/commodore+vic20_mametest",
+
         # MAME's ROM configuration is for the graphics keyboard, but MAME's
         # hardware emulates the business keyboard, so we can't interact with the
         # system.
         # "src/arch/commodore+pet4032_mametest",
+
         # MAME's ROM configuration is for the business keyboard, but MAME's
         # hardware emulates the graphics keyboard...
         # "src/arch/commodore+pet8032_mametest",
+
         # Works locally, but not on github CI.
         # "src/arch/apple2e+mametest",
+
         # Fails everywhere.
         # "src/arch/atari800+mametest",
+
         "src/arch/oric+mametest",
     ],
 )

include/zif.inc

@@ -10,14 +10,22 @@
 .set zloopsp, 0
 .set zifsp, 0
 
+.macro blt label
+    bcc \label
+.endm
+
+.macro bge label
+    bcs \label
+.endm
+
 .macro zproc name, sect=.text, binding=global
     .section \sect, "ax"
     .\binding \name
     \name:
 .endm
 
-.macro zlproc name, sect=.text, binding=global
-    zproc \name, .text, local
+.macro zlproc name, sect=.text
+    zproc \name, \sect, local
 .endm
 
 .macro zendproc

src/arch/commodore/bios1541.S

@@ -0,0 +1,212 @@
+; CP/M-65 Copyright © 2022 David Given
+; This file is licensed under the terms of the 2-clause BSD license. Please
+; see the COPYING file in the root project directory for the full text.
+
+#include "zif.inc"
+#include "cpm65.inc"
+
+ZEROPAGE
+
+.zeropage ptr
+.zeropage ptr1
+
+dma:             .fill 2
+
+sector_num:      .fill 3 ; current absolute sector number
+buffered_sector: .fill 3 ; sector currently in disk buffer
+
+; Initialises the disk library.
+
+zproc bios1541_init, ".init"
+    lda #0
+    sta buffer_dirty
+
+    ldy #3
+    zrepeat
+        lda #0
+        sta sector_num-1, y
+        lda #0xff
+        sta buffered_sector-1, y
+        dey
+    zuntil eq
+
+    rts
+zendproc
+
+; Sets the current DMA address.
+
+zproc bios_SETDMA
+    sta dma+0
+    stx dma+1
+    clc
+    rts
+zendproc
+
+; Select a disk.
+; A is the disk number.
+; Returns the DPH in XA.
+; Sets carry on error.
+
+zproc bios_SELDSK
+    cmp #0
+    zif ne
+        sec                 ; invalid drive
+        rts
+    zendif
+
+    lda #<dph
+    ldx #>dph
+    clc
+    rts
+zendproc
+
+; Set the current absolute sector number.
+; XA is a pointer to a three-byte number.
+
+zproc bios_SETSEC
+    sta ptr+0
+    stx ptr+1
+    ldy #2
+    zrepeat
+        lda (ptr), y
+        sta sector_num, y
+        dey
+    zuntil mi
+    clc
+    rts
+zendproc
+
+zproc bios_READ
+    jsr change_sectors
+    zif cc
+        lda sector_num+0
+        ror a               ; bottom bit -> C
+        lda #0
+        ror a               ; C -> top bit, producing $00 or $80
+        tax
+
+        ldy #0
+        zrepeat
+            lda disk_buffer, x
+            sta (dma), y
+            iny
+            inx
+            cpy #$80
+        zuntil eq
+
+        clc
+    zendif
+    rts
+zendproc
+
+; On entry, A=0 for a normal write; A=1 to always flush to disk.
+
+zproc bios_WRITE
+    pha
+    jsr change_sectors
+    zif cs
+        pla
+        sec
+        rts
+    zendif
+
+    lda sector_num+0
+    ror a               ; bottom bit -> C
+    lda #0
+    ror a               ; C -> top bit, producing $00 or $80
+    tax
+
+    ldy #0
+    zrepeat
+        lda (dma), y
+        sta disk_buffer, x
+        iny
+        inx
+        cpy #$80
+    zuntil eq
+
+    lda #$80
+    sta buffer_dirty
+
+    pla
+    zif ne
+        jmp flush_buffered_sector
+    zendif
+
+    clc
+    rts
+zendproc
+
+; Returns C on error.
+
+zproc change_sectors
+    ; If the buffered sector is the one we want, just return.
+
+    lda sector_num+0
+    and #$fe
+    cmp buffered_sector+0
+    zif eq
+        lda sector_num+1
+        cmp buffered_sector+1
+        zif eq
+            lda sector_num+2
+            cmp buffered_sector+2
+            zif eq
+                clc
+                rts
+            zendif
+        zendif
+    zendif
+
+    ; We need to change sectors. Flush the current one?
+
+    jsr flush_buffered_sector
+
+    ; Now read the new one.
+
+    lda sector_num+0
+    and #$fe
+    sta buffered_sector+0
+    lda sector_num+1
+    sta buffered_sector+1
+    lda sector_num+2
+    sta buffered_sector+2
+
+    jsr buffered_sector_to_lba
+    jmp read_sector
+zendproc
+
+; Compute the current LBA sector number in XA for the buffered sector.
+
+zproc buffered_sector_to_lba
+    lda buffered_sector+1
+    lsr a
+    tax
+    lda buffered_sector+0
+    ror
+    rts
+zendproc
+
+zproc flush_buffered_sector
+    bit buffer_dirty
+    zif mi
+        jsr buffered_sector_to_lba
+        jsr write_sector
+
+        lda #0
+        sta buffer_dirty
+    zendif
+    rts
+zendproc
+
+.bss
+
+.global directory_buffer, disk_buffer
+directory_buffer: .fill 128
+disk_buffer:      .fill 256
+buffer_dirty:     .fill 1 ; non-zero if sector needs flushing
+
+; DPH and DPB for drive 0 (our only drive)
+
+define_dpb dpb_1541, 136*10, 1024, 64, 0
+define_dph dph, dpb_1541