Tag Archives: old-computers

Amiga and DIY 68000 single board computer.

Started working on my breadboard version of a 68k computer.
When it’s working, I’ll make a PCB version.
Using almost only parts I still have. (No 8mhz crystal)

The 68000 being 24 bit address and 16 bit data needs 2x 8-bit roms and 2x 8 bit ram, but i didn’t have the components yet in this picture.

While tinkering with above, my Fatter Agnus chip came in.

To make a 1mb chipmem version of your rev 5 amiga (PAL)

You need to have a newer version of the Agnus chip (I had 8371, and bought a 8372a) AND you need a 512kb trapdoor memory expansion.

An unmodded rev 5 will see 512kb Chip mem and 512 Fast mem.

Replacing the Agnus 8371 for 8372a:
I lost my PLCC puller, so I modded a paperclip into a puller 🙂

When placing the new chip, I had to tape pin 41 for PAL version.
I used Polyimide Film tape.

Next I had to cut the jumper 2 connection and solder the other pads.
(Bottom and middle disconnect and middle and top bridged)

Next was another cut on the PCB, this disables the trapdoor card detection.


C64 code re-learning stuff

Re-learning the little I knew (I never had a c64 as a kid).
Back to basics, welll machine code I mean.

Programming a little demo using acme.
Split screen bitmap and text mode plus sid music

Running a little demo in retrodebugger (missing the sid music in the recording)

Some useful commands

; Dump prg with offset 0x800 per byte and skip 00 00 lines
xxd -o 0x800 -g1 icecrew.prg | uniq -f10

; Write symbol list
acme -l icecrew.sym icecrew.asm

; png to kla (koala picture)
retropixels icecrew.png -o icecrew.kla

; relocate a sid address
sidreloc -r org.sid new.sid

Below code has some flaws:

Many empty gaps, creating a large file.
Exomizer could fix this, but better memory management should be the better solution.
The Koala file has many 0 bytes, the logo is small but the file is created for a full screen image.

Part of the program see $1000 of start of SID music

!cpu 6502
!to "icecrew1.prg",cbm

; Standard basic sys runner
basic_address   = $0801

; sid addresses
; address moved using 
; sidreloc -r Lameness_Since_1991.sid lame.sid
; addresses found using
;sidplay2 -v lame.sid 
;|   SIDPLAY - Music Player and C64 SID Chip Emulator   |
;|          Sidplay V2.0.9, Libsidplay V2.1.1           |
;| Title        : Lameness Since 1991                   |
;| Author       : Peter Siekmann (Devilock)             |
;| Released     : 2017 Oxyron                           |
;| File format  : PlaySID one-file format (PSID)        |
;| Filename(s)  : lame.sid                              |
;| Condition    : No errors                             |
;| Playlist     : 1/1 (tune 1/1[1])                     |
;| Song Speed   : 50 Hz VBI (PAL)                       |
;| Song Length  : UNKNOWN                               |
;| Addresses    : DRIVER = $1C00-$1CFF, INIT = $0FFF    |
;|              : LOAD   = $0FFF-$1B25, PLAY = $1003    |
;| SID Details  : Filter = Yes, Model = 8580            |
;| Environment  : Real C64                              |
sid_address     = $0fff
sid_play        = $1003
sid_init        = $0fff
; Character 
char_address    = $3800
screen_mem      = $4400
; Koala address
bitmap_address  = $6000
bitmap_data     = $7f40
bitmap_color    = $8328
bitmap_bgcolor  = $8710
program_address = $c000
color_mem       = $d800

reg_d011	= $D011
; VIC register
;Bit 7 (weight 128) is the most significant bit of the VIC's nine-bit raster register (see address 53266).
;Bit 6 controls extended color mode
;Bit 5 selects either the text screen ("0") or high resolution graphics ("1").
;Bit 4 controls whether the screen area is visible or not.
;Bit 3 selects 25 (when set to "1") or 24 (when set to "0") visible character lines on the text screen.
;Bit 0–2 is used for vertical pixel-by-pixel scrolling of the text or high resolution graphics.

; Rom routine to clear screen ( slow ! )
; Better to do this yourself
clear_screen     = $e544

* = sid_address
    !bin "lame.sid",,$7c+2

; standard charset
* = char_address
    !bin "charset.chr"

; drawn with gimp converted using retropixel
; retropixels icecrew.png -o icecrew.kla
* = bitmap_address
    !bin "icecrew.kla",,$02

; sys 49152
* = basic_address
    !byte $0d,$08,$dc,$07,$9e,$20,$34,$39,$31,$35,$32,$00,$00,$00

* = program_address
    ; init
    lda #$00
    jsr sid_init
    jsr clear_screen
    jsr load_bitmap
    jsr init_text
    ldy #$7f
    sty $dc0d
    sty $dd0d
    lda $dc0d
    lda $dd0d
    lda #$01
    sta $d01a
    lda reg_d011
    and #$7f
    sta reg_d011
; move interrupt vector to bitmap
    lda #<interruptbitmap
    ldx #>interruptbitmap
    sta $314    ; Low Address part IRQ vector
    stx $315    ; High Address part IQR vector
    ldy #$1b
    sty reg_d011
    lda #$7f
    sta $dc0d
    lda #$01
    sta $d01a
; trigger interrupt at rasterline 0
    lda #$00
    sta $d012
    jmp *

    inc $d019
; trigger interrupt at rasterline 128
    lda #$80
    sta $d012
    lda #<interrupttxt
    ldx #>interrupttxt
    sta $314
    stx $315
    jsr bitmap_mode
    jmp $ea81

; ack IRQ
    inc $d019
; IRQ at line 0
    lda #$00
    sta $d012
    lda #<interruptbitmap
    ldx #>interruptbitmap
    sta $314
    stx $315
    jsr text_mode
    jsr sid_play
    jmp $ea81

; bitmap graphics multicolor
    lda #$3b
    sta reg_d011
    lda #$18
    sta $d016
; switch to video bank 2 ($4000-$7FFF)
    lda $dd00
    and #$fc
    ora #$02
    sta $dd00
    lda #$18
    sta $d018

; set text mode hires
    lda #$1b
    sta reg_d011
    lda #$08
    sta $d016
; switch to video bank 1 ($0000-$3FFF)
    lda $dd00
    and #$fc
    ora #$03
    sta $dd00
; set charset location
; 7 * 2048 = $3800, set in bits 1-3 of $d018
    lda $d018
    ora #$0e
    sta $d018

    lda bitmap_bgcolor
    sta $d020
    sta $d021
    ldx #$00
; screen memory
    lda bitmap_data,x
    sta screen_mem,x
    lda bitmap_data+256,x
    sta screen_mem+256,x
    lda bitmap_data+512,x
    sta screen_mem+512,x
    lda bitmap_data+768,x
    sta screen_mem+768,x
; color memory
    lda bitmap_color,x
    sta color_mem,x
    lda bitmap_color+256,x
    sta color_mem+256,x
    lda bitmap_color+512,x
    sta color_mem+512,x
    lda bitmap_color+768,x
    sta color_mem+768,x
    bne copy_bmp

    ldx #$00
    lda text1,x
    sta $0400+520,x
    lda text2,x
    sta $0400+640,x
    lda text3,x
    sta $0400+640+120,x
    lda #$06
    sta color_mem+520,x
    lda #$0e
    sta color_mem+640,x
    lda #$0e
    sta color_mem+640+120,x
    cpx #$28
    bne copy_txt

    !scr  "     back to oldskool demos in 2024     "
    !scr  "   greetings to bigred & tyrone & edk   "
    !scr  "     a lot to relearn - keep coding!    "

C64 Multipart Loader

Today I tested part loading for a demo.

I wanted this to be a multipart loader, instead of a trackloader.
A trackloader can load sector parts which I would like more.
But the C64Pico can’t do disk images. (Mcume)

C64Pico based on MCUME see building of this in other posts.

2nd reason: While I’ve written a track loader for 8086, I never did it for C64. As a kid I didn’t have a C64, so all knowledge I have is from later years.
I’ve written only a few C64 machinecode programs.

See below explanation of what happens
  • Showing makefile
  • Showing first part assembly (without text Hello 2nd part)
  • Showing second part (no sysheader) needs to be loaded at $2000
  • Compile using Acme
  • make disk image
  • and run using autostart x64 (Vice emulator)

You see the first text from the 1st assemby code, then it will load the second at $2000 and does a jmp to this address.
Second text will but displayed.

While i’ve been using KickAss in the past and some other 6502 compilers, I manly use acme.

Makefile I created to compile, create a C64 diskimage and run the program is as below. (No exomizer tools in this Makefile)

all: acme disk run

	acme testloader.asm
	acme 2ndpart.asm

	c1541 -format diskname,id d64 my_diskimage.d64 -attach my_diskimage.d64 -write loader.prg loader.prg -write 2nd 2nd

	x64 my_diskimage.d64 

C64Pico part 3

Today we worked on this project again. (Bigred and me)

There were some problems we needed to fix since last time:

  • It was quite hard to get the correct parts.
    Our display connector was only fitted with connection pins on the wrong side of the connector. (up/down)
    So I bought a connector with both positions populated.
    So we had to replace this hard to solder (40 pin) connector.
  • It was not clear what the orientation should be of the atmega328pb.
    We looked at the pinout, and followed the VCC/GND. But these are also available of the opposite side of the chip. (We missed that)
    Later, we saw a tiny line on the PCB, which showed the pin 1 placement.
    So we had to remove and replace the chip.
    When turning on the power, (with incorrect placement) probably fried R5 (10k resistor), on both our boards.
    Had to replace those also.
  • Programming the atmega328pb was not easy, see below fixes.
  • Compiling the pico firmware resulted in a black screen.
    Below the fixes I had to make to get the screen working.

Other things still to fix.

  • Bigreds screen.
  • atmega328p didn’t work for Bigred, so probably needs to replace with the pb version.
  • My battery controller is not charging.
    See bottom of page
  • Some of my buttons are working. The pewpew and some of the cursor keys (not as I expect, there are some up/down issues)
    And none of the other keys are working.

Some other things we noticed.

  • sdcard: remove partitions, format using mkfs.exfat
    Create a c64 directory on this filesystem where you can put the d64 files!
  • 0402 SMD is far too small for me.
    There is enough room on the board to use 0805 for example.
    Even THT is possible, there are only a few components.
  • Some components are TOO close together, removing a component resulted in other small parts disconnecting also.

My friend Bigred said: If I can see it, I can solder it.
But it is not easy. This probably keeps a lot of people from building it!

Below the diff from the source we got from:


UPDATE 20240501: We needed to clone the c64pico branch!

git clone -b c64pico https://github.com/silvervest/MCUME.git

Then it worked with the screen and keyboard!

Programming the atmega328pb using usbasp

Link above shows the programmer.

To get your Arduino IDE up and running

  • Open the Arduino IDE.
  • Open the File > Preferences menu item.
  • Enter the following URL in Additional Boards Manager URLs:https://mcudude.github.io/MiniCore/package_MCUdude_MiniCore_index.json
  • Open the Tools > Board > Boards Manager… menu item.
  • Wait for the platform indexes to finish downloading.
  • Scroll down until you see the MiniCore entry and click on it.
  • Click Install.
  • After installation is complete close the Boards Manager window.

Above settings worked for me, maybe you can also try Programmer: usbasp (slow)

First install the bootloader.

When compiling the keyboard program of silvervest, you can find “Upload using programmer” in the Sketch menu!


Maybe I’ve got a problem with the ground plating of the charger.
Also very hard to solder the sides!

Amiga Action Replay

A long time ago I had an Action Replay II.

I modded it and was planning to rebuild this using pluggable eurocard-prints.
Then it got lost, somewhere.

Today I went to Almelo with Tyrone.
In the morning reverse engineering a lift controller print, and afternoon going to a guy selling a lot of Retro stuff.

And there it was, an Action Replay II for Amiga just catching dust.

I had to buy it, and got a sh*tload of 27256 Eproms for free!

Action Replay Mk I

This version is compatible with the A500/A1000 version only. It also plugs into the side expansion port. It introduces the following features:

1.0 Version

  • Shows and modifies registers (even read-only ones) and memory contents.
  • Trainer maker.
  • M68000 assembler / disassembler.
  • Copper assembler / disassembler.
  • Sprite editor.
  • Virus detector.
  • Picture / music (tracker format) / sample ripper.
  • Save computer memory (freezed programs) to disk.
  • Shows computer status (disk parameters, ChipRAM, FastRAM…).

Features added to the 1.5 Version

  • Mempeeker.
  • Ability to save freezed programs to RAM.
  • RAM testing.
  • Illegal opcode – jumps to freezer mode.

Action Replay Mk II

A special A2000 version is available for this particular revision. Instead of plugging into the side expansion port it plugs into the 86 pin CPU slot.

Features added since MK 1.5 version

  • Boot selector.
  • Picture editor.
  • Sound tracker.
  • Turbo fire manager (separately for both joysticks).
  • Disk encoder.
  • Start menu.
  • Disk monitor.
  • Integrated DOS commands (Dir, Format,…).
  • Diskcopy.
  • 80 characters display with two-way scrolling.
  • Calculator.
  • Notepad.
  • Memory and drive switch (enabling / disabling).
  • Music ripper now finds all tracker formats (SoundTracker, NoiseTracker, other formats with 32 samples).
  • Ripped music / pictures are saved in IFF format.

C64Pico Follow-up

Soldering almost done, except for the space bar all tactile buttons in place.

Using my USBasp programmer I tried to program the Atmega328pb.

Same one I used for:

I first needed to implement some udev rules to get the rights for the reader correct.

SUBSYSTEM=="usb", ATTRS{idVendor}=="16c0", ATTRS{idProduct}=="05dc", GROUP="dialout"

Next I tried to burn a bootloader.

Well, not as planned, back to the drawing board.

Hopefully I compiled at least the Pico part correctly.

Started working on C64Pico with Bigred

A week ago I got the last components delivered to my doorstep.

This project was made by Silvervest and it’s f*ckin awesome.


I was afraid to start this myself, SMD is on another level for me.
But my good friend Marco said … No problem!

So I ordered components online, which was not easy.
Selecting the correct parts, sizes and options.

These things are really really small

Using tweezers to place the components was even difficult.
The slippery tiny bastard got catapulted everywhere. (Or got stuck on fingers, soldering iron and alike)
Many small components got lost into the 7th dimension. Never to be found again.

Awesome to work on this together, but Marco said that I have to try it myself.
Welllll, I got 3/4 of the ATmega328PB-A perfectly soldered, then I notished that it was crooked.
Desoldering was a mess, and I heated the PCB TOO much with the heatgun.

My messed-up PCB, and f*cked-up IC. Leave it to the professionals.

Next step for me is soldering the 75 mini buttons!

Got a Trinitron display from him, I was looking for this for a long time.

A “new” sound chip for 6502

UPDATE: 20240225

I’ve written about General Instrument AY-3-8910 before, here is some work I did today.

This sound chip i wanted to implement in my amiga, and now it’s a alternative for my 6502 computer. ( As an alternative setup for the SID chip. )
Btw this is the same kind of chip used in the Atari ST.

A clean setup … I’ve got the sound chip and a Amplifier chip.

Above a Kicad drawing I made today, a little different from my design from the 90’s.

Below a movie clip I recorded today. Running a test setup using an Arduino nano and a sdcard reader.
The sound is bad, this is due to clipping and the absence of multiple resistors and capacitors.
Music is a register dump from a YM music file.
Amplifier is a bare LM386.

UPDATE: 20240225

I don’t like tying those three outputs together, and amplifying those.

So I’m going to use a LM324 i’ve got left from my 8085 interface, and make a 3-channel amplifier.

Something like this

Soldering a 6502 PCB

A while ago I started a soldering a 6502 bare SBC.

Note pin 1 is not connected, VPB (vector pull is not supported on this PCB. But i’m planning to design a new one anyway.)

I got it running now.

It has an EPROM with Wozmon and Basic for now.
I have to redo the address decoder, but I like the simple serial interface by Geoffrey. (I hate the PIC18F15Q41, made by Microchip, but still the best minimal option .. for now)

Probably the last time i’ve used a pic was in 1998


I’ve posted in the past something about pl/m.
Today i got this running again in a dosbox.

The PL/M programming language (an acronym of Programming Language for Microcomputers) is a high-level language conceived and developed by Gary Kildall in 1973 for Intel’s microprocessors.

A link to information about Gary, and ebook (pdf) he wrote.

We learned to program PL/M at school (MTS)

Below the compiler and lib files


Example program Tic Tac Toe I wrote in 1990

Compiling a PLM source code


Tic Tac Toe in PLM

/*DOEL:                                              */
/*Dit programma is boter kaas en eieren voor twee    */
/*spelers, er wordt gecontroleerd of iemand gewonnen */
/*heeft. (Je speelt niet tegen de computer)          */
/*UPDATE:12/2/90,15/2/90,18/2/90  RELDATE:19/2/90    */
/*PROGRAMMER:H.M.Aanstoot                            */
/*UPDATE 5/3/90 1:13:23                              */
/*De volgende 4 regels zorgen ervoor dat de compiler */
/*de PLM  DOS,UTIL routines die op disk staan        */
/*meestuurt naar de linker                           */
/* bla bla 2de versie met STRINGS!! eindelijk gelukt */

dcl naam(3)           pointer;
dcl plaats(9)         word;
dcl teken(2)          pointer;
dcl aanzet            word;
dcl loop              word;
dcl a                 word;
dcl winnaar           word;
dcl nummer            word;
dcl item              word;
dcl error_status      word;

call dsso(naam(aanzet));
call dsso(@(', geef een getal: $'));
if nummer<1 or nummer>9 then goto invoer;
if plaats(nummer)<>0 then goto invoer;
call dso(nummer+48);
end spelerzet;

call dsso(@(cr,lf,'+-----+-----+-----+',cr,lf,eos));
call dsso(@('|     |     |     |',cr,lf,eos));
call dso(124);call zet;call dso(124);call zet;call dso(124);call zet;
 call dsso(@(124,cr,lf,eos));
call dsso(@('|     |     |     |',cr,lf,eos));
call dsso(@('+-----+-----+-----+',cr,lf,eos));
call dsso(@('|     |     |     |',cr,lf,eos));
call dso(124);call zet;call dso(124);call zet;call dso(124);call zet;
 call dsso(@(124,cr,lf,eos));
call dsso(@('|     |     |     |',cr,lf,eos));
call dsso(@('+-----+-----+-----+',cr,lf,eos));
call dsso(@('|     |     |     |',cr,lf,eos));
call dso(124);call zet;call dso(124);call zet;call dso(124);call zet;
 call dsso(@(124,cr,lf,eos));
call dsso(@('|     |     |     |',cr,lf,eos));
call dsso(@('+-----+-----+-----+',cr,lf,eos));

  call dsso(@('    1   2   3',cr,lf,eos));
  call dsso(@('    4   5   6',cr,lf,eos));
  call dsso(@('    7   8   9',cr,lf,eos));
end update;

if plaats(item)=0 then call dsso(@('     $'));
if plaats(item)=1 then call dsso(@('  X  $'));
if plaats(item)=2 then call dsso(@('  O  $'));
end zet;

   do a=1 to 2;
   if plaats(1)=a and plaats(2)=a and plaats(3)=a then winnaar=a;
   if plaats(4)=a and plaats(5)=a and plaats(6)=a then winnaar=a;
   if plaats(7)=a and plaats(8)=a and plaats(9)=a then winnaar=a;

   if plaats(1)=a and plaats(4)=a and plaats(7)=a then winnaar=a;
   if plaats(2)=a and plaats(5)=a and plaats(8)=a then winnaar=a;
   if plaats(3)=a and plaats(6)=a and plaats(9)=a then winnaar=a;

   if plaats(1)=a and plaats(5)=a and plaats(9)=a then winnaar=a;
   if plaats(3)=a and plaats(5)=a and plaats(7)=a then winnaar=a;
end check;

naam(1)=@('Speler 1$');
naam(2)=@('Speler 2$');
do a=1 to 9; plaats(a)=0; end;

    do loop=1 to 9;
    call update;
    call check;
    if winnaar<>3 then goto gewonnen;
    call spelerzet;
call update;
call dsso(naam(winnaar));
call dsso(@(' heeft gewonnen',cr,lf,eos));
if winnaar=3 then call dsso(@('Helaas, pindakaas!$'));
			 else call dsso(@('Gefeliciteerd ermee!$'));

call dexit(error_status);