I’m manually making some cheats for a few games I have, I’ve done quite a few already for NES, SNES, Genesis. Now I wanted to do a few for the Sega CD / Mega CD, but it appears that something is different with the games or that ties with RetroArch’s cheat engine.
I’ve already made a working cheat for Flashback - The Quest For Identity (USA), and now I attempted to do one for Mickey Mania - The Timeless Adventures of Mickey Mouse (USA), but it simply does not work. I have little doubt that I am doing things correctly because I even did a few cheats for the exact same game for the Genesis, but something isn’t quite right with this one.
Example: game starts with 4 lives, on the Genesis I would start with a 4-bit search for the value 4, then lose a life and search for the value 3, and so on. I will find a match at this point and it works fine. With the Sega CD version this approach does not yield any result. What is more puzzling is that I went as far as doing 32-bit searches by approximation (equal, not equal) and even then I cannot find any address that holds a value as simple as the number of lives.
So, the question is, what is different about the SegaCD or some of its games that the built-in cheat engine does not find anything usable for a particular game like Mickey Mania - The Timeless Adventures of Mickey Mouse (USA)?
I have a theory from some reading I did, the theory goes that the Sega CD (and its emulation) uses a special type of RAM that the cheat engine cannot access (or is scrambled somehow, don’t know). And the reason why I was lucky with * Flashback - The Quest For Identity (USA)* is because that game may be borrowing the Genesis part of the RAM and there the cheat engine can see and touch properly.
Here’s a quote from a forum post I found which leads to this reasoning:
Simply put, those are Sega CD RAM (or PRG RAM) cheats, which (as far as I know) no emulator supports. The FF-style RAM cheats work because some CD games use “Genesis” RAM for things. A good example of this is Sonic CD, thus some emulators like Genesis Plus GX and the MegaSD flash cart support them. To use PRG RAM cheats you’d probably have to use something like Cheat Engine or ArtMoney with an emulator to get them working. I believe lee4 has a signature link to a tutorial on using ArtMoney to cheat with Sega CD games.
It’s actually not as simple as creating a cheat that uses the Genesis RAM either since the game could be using PRG RAM (or Word RAM) for such things which I believe Lunar Eternal Blue is an example of.