Posted By: wraggster
Eke-Eke has posted a great update on his new site about improvements made to the Genesis emulator for the Gamecube and Wii, heres the details:
I decide recently to rewrite completely the EEPROM emulation code used in Genesis Plus. The previous one was based on Notaz’s Picodrive sourcecode but I was not really satisfied with it since it was not compatible with some games (Rings of Power, College Slam, Micromachines’ serie, …) and, beside from preventing game backup to work properly, also make some games crashing.
Since not so many Genesis games used serial EEPROM as backup RAM, this feature is generally not supported by the Genesis emulators out there (so far I know, only Kega, Picodrive and Jenesis support this, but none of them seem to have a full support).
The emulation itself is not very difficult since EEPROM datasheets (24Cxx eeprom are generally used) are freely available and the communication protocol is quite easy to reproduce. The main difficulty was to determine which games indeed use serial EEPROM (instead of classic parallel SRAM) and also which type of EEPROM it is and which type of EEPROM mapper they are using.
After testing many games on the emulator, I finally get some results and a list of games using EEPROM and their characteristic. I compiled this in a document, which emulators authors may find useful. In this document, there is also a quick note about EEPROM access protocols, which actually cover the three EEPROM’s modes found to be used. Interested people could also have a look at eeprom.c in the genesis plus SVN base.