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Topics - patrickmollohan

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Newcomer's Board / NES Mapper Conversion
« on: February 27, 2020, 10:44:48 pm »
I have acquired an MMC3-based multicart NES ROM that uses a rather obscure mapper (534) and would like to convert it to a more common mapper for use with other emulators. As I am new to ROM hacking in general, a mapper conversion may not be the best place to start learning, but I would love to figure it out anyway.
With this particular ROM, I edited the iNES header to test other MMC3 multicart mappers. I found that mapper 52, which is supported by most emulators, at least somewhat works (although the menu graphics are slightly glitchy, and the individual games are very corrupted). However, in comparison to the other mappers I've tried, this is a much better start, as the others either don't boot at all, or will boot into one of the individual games (with corrupted graphics) as opposed to the menu like it should. Am I at least on the right track to figuring out what mapper to convert to? I assume I wouldn't be able to patch it to straight MMC3 for better compatibility, correct?
After the appropriate mapper is selected, what is the next step in the process? I have opened the original and modified ROM in FCEUX in order to view the debugger, but mapper 534 is not supported in the emulator (and thus produces nothing useful in the debugger), and I'm not sure if it is okay to view the debugger with just the iNES header changed. If it is, what would I be looking for to fully patch the game? What are the steps involved with this process?
Finally, although I have searched high and low, I could not find any tutorials on mapper conversions, but I would greatly appreciate any general tutorials, advice, tips, etc. on the subject. Anything at all would be really useful!
Thank you for your time!

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