So thanks to BigFred from no-intro, I got my hands on more Sachen cartridges.
A few were mono cartridges, which I managed to dump using my 4B-007 code.
Unlocking color cartridges, which are compatible with CGB as well as DMG works just fine in DMG mode. However, the internal mechanics work differently, so I’ll have to update the wiki shortly. Figuring out how to unlock them in CGB mode took quite some time, because I forgot to mark the #CS signal as being connected to the mapper 😉 CGB and DMG mode do not refer to whether or not the game will run in color, they actually do make use of common Game Boy identification methods.
Well, anyway, I figured out how to unlock them in CGB mode as well and I believe I have a correct state machine figured out. I got to contribute some code to higan to properly emulate these mappers, but I digress.
So the actual pretty fucking huge deal is that many of the regular 4B color cartridges actually contain multiple ROMs in them and — depending on some solderable/cuttable links on the PCB — boot up in 8B-mode or
16-in-1 (16B anyone?) 16B-mode. Currently checking back with BigFred if he’s OK with me cutting some traces on his game PCBs though…
So yeah, exciting news. I also prepared schematics for most of them, though documenting chip-on-board is somewhat bothersome. I’m also convinced that they used 3D wire bonding technology and for some reason ROMs that are much bigger than their games — that must have been expensive… For instance, Thunderblast Man is 2 Mbit, yet its Chinese counterpart requires 4 Mbit to function correctly and
has an 8 Mbit thus contains another 2 Mbit ROM 🙂
So guessing some pinouts for them isn’t so straightforward 😐 But I’ll do my best guesstimate and that has to be enough, I guess.