SCHG:Sonic CD 510 Beta
From Sonic Retro
This is the Sonic Community Hacking Guide for Sonic the Hedgehog CD (prototype 510). Sonic CD, as with all Sega CD games, uses a filesystem with files for each code event instead of a monolithic rom. Splash screens, menus, and levels all reside in their own .mmd file with optional .bin files for SubCPU execution.
As each MMD runs separately of others (except for those which load to RAM), various pieces of code and data are repeted throughout like MMD files. This makes art editing without a disassembly very long and tedious. However, upon the release of a disassembly of Sonic CD 510, all common art and code will be consolidated so changes are reflected in every MMD including that data.
The level MMDs have the filename format RXYZ__.MMD: