I started working in the so called "2gen BIOS". The menu simply doesn't work for now :P (I didn't even program it, just it shows some options but I think I'm gonna rewrite it from scratch again). But the BIOS as itself works and will load the ROMs. Some ROMs don't run yet, I gotta fix that, and also the Action Replay BIOS won't work as it has an invalid header (the option "Force ROM" (gotta change that name :P) is meant to force ROM booting even if no valid cart has been detected, in order to allow those ROMs to work). About the internal SRAM (it'll have an internal SRAM so if 2gen games detect the 2gen BIOS they'll be allowed to use it if they don't care), I don't know what its size will be. I though that 64KB was going to be few, but apparently the Sega CD has only 8KB of internal SRAM and the RAM carts are 64KB (before you ask, the manual says that the Sega CD has 64 kiloBITS, not kiloBYTES). This explains why some games take up so many blocks, there are just 64 bytes per block... This is the very little I have for now: http://www.fileden.com/files/2006/12/22/543510/2GenBIOS.bin
It almost makes me wish I could make some uber cool BIOS. Nice work, although I don't see any real use for it yet. :P
And you won't until I get the menu working. The BIOS will allow you to test your devices, try to make run some ROMs that the normal BIOS wouldn't allow you to run, check ROMs and also has an internal SRAM, so the future 2gen games will be able to use it. Another thing: you can cause the menu to appear by loading the BIOS. The BIOS will check against itself and will act as if no cart was inserted if that case. This is done in order to check what will happen when no cart is inserted in emulators. And the menu is NOT working. Later I'll post the source code, feel free to steal that font if you want EDIT: typo.