Sunday, February 17, 2019

PAiA 8700 Schematic Redraw

The PAiA 8700 computer is an optional part for the PAiA 4700 modular system. It gives you the ability to run software like a "pink music" generator.

I took interest in it because it combines my favorite CPU, the 6502 (6503 here), and analog synthesis. It's pretty hard to find one these days, but PAiA published the schematics and they're still available. I needed them in Eagle CAD format to be able to work on them, so I redrew them here. In the process, I like to think I've improved the clarity and layout of the schematic.
The board is as close a reproduction as I could manage.

I've also typed out the original assembly source file and assembled binary.

Files available on my github

Also, a memory map. Why not?

I was able to find some NOS and begin assembling a brand new 8700 reproduction. More to come.


  1. Awesome. I`ve been thinking of replicating the 8700 (and its software), plus a MIDI in, with an arduino.

    1. Very cool. It should be pretty simple to rewrite the firmware. You could almost port it opcode for opcode!
      Something more powerful would be able to emulate the 6502 core and run the original binaries.

      Let me know if you make any progress or want to throw around some ideas.

  2. I got as far asdrawing and writing down some ideas, and talking to some people.
    I also found a 6502 emulator.

    I want to send you some files. How can I do it?

    1. Cool. The link to the 6502 emulator isn't working for me. That may or may not do the trick.

      Another option is this 6502 based microcontroller:

      The files, if they're small, you can email them tome at

  3. It`s 61MB 7zipped. Is WeTransfer an option?
    The 6502 emulator is included.

    Also this:

    1. I've never used WeTransfer, but it looks like it should work. I use mediafire and Google Drive.

      The emulator looks like a good starting point. You'd have to strip out the monitor program, repurpose the terminal for MIDI and add in emulation of the IO. Performance will probably be the limiting factor.

    2. OK. Here`s a drive link.

  4. Any updates on this project?
    I have a Paia 2700,4700, and 8700 with computer controller keyboard. I'm just starting to learn how to use it but been buying modules since 1993 slowly. I'm also looking for all the programs on for the 8700. I still have a cassette tape deck, so I could possible interface it lot load the programs.

  5. you can email me directly at "info @ sajtron . com"