M93C46 programing

mrraymrray · September 20

I have several Jaguar cartridge boards that I am "repopulating" and one of the components is a M93C46 chip (U3 in the attached photo). Does anyone know if this chip requires programing and does anyone have information (or code) for writing this chip? I also understand that this chip can be replaced with either a 93c66 or 93c86. What are the advantages of this swap?

Zerosquare · September 20

It's the EEPROM chip that is used for saving high scores and game progression. It doesn't need to be programmed beforehand, the game will initialize it if is empty.

The standard chip (93C46) can store 128 bytes, and is used by all commercial games and most homebrew games. Some homebrew games require a 93C66 (512 bytes) or 93C86 (2 kilobytes) chip instead. You have to use whichever chip the game is designed for ; a different one won't work (even if the capacity is larger).

dilinger · September 21

Out of curiosity.

What could be the maximum size possible for an EEPROM chip on a cartridge?

Zerosquare · September 21

If you want a "plug-and-play" replacement chip, 2 kilobytes is the largest you can use.

But it is possible to interface much larger EEPROM chips (e.g. 256 kilobytes) by adding a logic inverter and using custom reading/writing code. Access is rather slow however, so it may or may not be useful in practice.