Working With Old High-Voltage EPROMs Is Fussy

EPROMs, those UV-erasable memory chips of the 80s and 90s, once played a crucial role in countless electronic devices. They’ve become relics of a bygone era, but for enthusiasts of vintage electronics, the allure of these light-sensitive devices remains strong. Today, we’re diving into [Kevin Osborn]’s nostalgic journey as he uncovers the secrets of old EPROMs loaded with Atari 7800 code.

[Kevin] used to work at General Computer Company, which produced the Atari 7800 and several games for the system. Thus, he had a handful of old carts and development EPROMs sitting up in his attic along with an old console. Recently, he decided to try and uncover what was on the EPROMs and begun an investigation. They wouldn’t run in his Atari, and he quickly realized why: the EPROMs weren’t cryptographically signed, so the system wouldn’t load them.

After a little work, he was able to dump the EPROMs with the help of a TL866II+ reader. After some hacking, he was able to fettle the data on the EPROMs into something that would run on the A7800 emulator. This was easy enough, as the emulator doesn’t run checks for properly signed code. From there, he was able to use a UV phone sanitizer to wipe the EPROMs, and re-burn them with signed versions of their original code. This took the application of some high voltage, but with the aid of an external power supply, it worked. He was able to successfully run the obscure ROMs on real Atari 7800 console hardware.

UV-erasable PROMs, or EPROMs, have long been superseded by the more convenient electrically-erasable PROMs, or EEPROMs. Their advent rapidly sped up embedded development for all of us, and should be greatly appreciated. If you’ve been tinkering with your own ancient retro finds, don’t hesitate to drop us a line.