C64 EEPROM Adapter

Top Side of the Adapter Board

Recently got my hands on an old Commodore 64 with bad mask ROMs (kernal, basic, character, etc). Luckily, I’ve got a huge stash of AT28C64B EEPROMs from back when I was working on Atari cartridges! After some side-by-side comparisons with the original mask ROM pinouts (2364 & 2332), I decided it was best to create a simple but effective general purpose adapter board to bridge the gap.

This was definitely one of my fastest PCB designs EVER in less than 1-2 hours from schematic to board to gerber files. So, have pity on me if there’s any glaring issues!

I’ve got a batch of boards on there way as of today, and if it all goes smoothly, I’ll probably add the leftovers to an online store of some form in case any of y’all are in the same boat as me! Heck, I might even give the option to include a pre-programmed and tested C64 ROM.

By the way, I tried out using PicoPROM to handle programming the chips. Took some getting used to using minicom for the xmodem+CRC file transfer, but very quick and effective otherwise! I think if some level-shifters were added in for read capabilities to verify the writing process, it could definitely be an effective and cheap alternative to the TL866 for writing EEPROM ICs.

I’ve also got an EEPROM programmer that I developed back in 2019. It’s nothing too special except for the fancy Python GUI. However, I haven’t tested it in many moons, so you may encounter a bug here or there depending on your application. Would love to squash those bugs, though! So, let me know if you do try it out. <3

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