I wanna make a Sega CD hack

but I haev no tuls to werk with 

i gots u

official sega cd programming docs
heres a sega cd tech demo i made in which u can use to see how a cd game is structured

sega cd adds an extra 68000 cpu (called the sub cpu, making the genesis cpu the main cpu), 256kb of shared ram (word ram, shared by both cpus), 512kb of ram only used by the sub cpu (prg ram) cd drive, 8 channel pcm, and graphics chip. sub cpu is used for interfacing with the cd hardware.

there are 2 ram modes, 2m and 1m/1m. 2m means the full 256kb is only accessed by 1 cpu at a time. 1m/1m splits ram in half and gives each cpu a piece. the ram mode also changes the graphics chip mode. 2m mode = using a table of values to stretch or rotate a tilemap, 1m/1m mode = converting pixel data into different formats (i.e. bitmap to tiles).

cd image data starts with a header, and then the initial program (which gets loaded into the start of genesis ram). first part of that should be the security code, or else it wont be recognized by the bios. after that is the sub cpu program (which gets loaded at $6000 in prg ram). after that is whatever you want, typically the cd files. cd games commonly used iso 9660, but if you want to, you can program the sub cpu to use a custom format.

you could also look at spritesmind for moar info.

hope this is helpful in some way, but for now i gotsa speed out 4 teh nite

Thanks Master