INES 4 Mapper

[NightsOnRepeat]

I've been looking everywhere for one. Any chance of this being added?

[kylewlacy]

After a quick skim online, mapper 4 is MMC3, which I believe is one of the most common mappers. I definitely want to see it added to GhidraNes! Unfortunately it's a relatively complex mapper, and so I personally won't have the capacity to implement it myself for some time

[matthewturk]

Hi @kylewlacy , I wanted to ask if you could say where the complexity comes in. Is it because the banks at 0x8000-0x9FFF and 0xC000-0xDFFF are switchable? (I'm new to the NES scene, and I've been reading the NESdev wiki alongside src/main/java/ghidranes/mappers/ to try to understand how they relate.) Thank you!

[kylewlacy]

MMC3 (according to NESdev) has 2 switchable PRG ROM banks, 2 fixed PRG ROM banks, and an optional PRG RAM bank (plus 6 switchable CHR banks, but we don't care about those). For GhidraNes, that means we need to iterate through the ROM and add/label each PRG bank, and also decide which banks are used by default. So it is more complex than the other mappers currently defined, but it's honestly not that complex overall. I think it would be fairly similar to the code for mapper 19, and that would probably be where I'd start when/if I try to add MMC3. I don't think it would be that much code overall, but this kind of file-offset/address manipulation code I find is easy to make errors in (at least for me!), so it can take some time to test and iterate

[NightsOnRepeat]

Thank you for the responses. You are a maniac for making such an awesome tool. Keep up the awesome work!

[kylewlacy]

(Reopening this issue to track support for mapper 4 / MMC3)