I work on simple Sonic hacks on the Genesis from time to time, and I would really like to port the Sega Screen used in Sonic 1 for the Game Gear (the one with the jumping Sonic):
While I can easily recreate it using brand new 68k code, I'd prefer to do something different as a proof of concept, if possible. Basically what I want to do is to take the original Z80 code for the Sega Screen from Sonic 1 Game Gear, and use it on the Genesis as untouched as possible. This brings up some interesting problems, though.
- I need the Z80 code from S1GG, but there is no disassembly, and Maxim from smspower said that the code for the Sega Screen is all over the place. I tried to disassemble it with smsexaminer, but the code is, indeed, a real mess;
- I need the original graphics for Sonic and the Sega Screen, but this is easy and already done;
- There is no emulator that supports Mode 4 while in Genesis Mode (afaik);
- The Z80 can't access the VDP while in Genesis mode, as it can only feed the VDP with 8-bit per time while the VDP expects 16-bit words in Genesis mode (this can be circumvented by letting the Z80 run the code and ask the 68k to just feed the VDP);
- The memory map for the Z80 is completely different while in Genesis mode (another easy fix);
- Probably something else.
Thanks in advance.