HOWEVER, it is immediately stuck after pressing start and cant move past the start screen. So I have the rom.smc, and the language patch.ips, and I can successfully boot it up in English using the for headered patch.

Then the last 0.25MBits is mirrored to match the 0.5MBit, so now we have a 1MBit part, and then the last 4MBits are mirrored once to match the 8MBit, so we'd have 16+ 8+ 2*(2+1+0.5+0.25+0.25mirrored) = 32MBit. Im having an issue trying to get Genealogy to work on the emulator snes9x.

However, I'm curious on what happens if the ROM is not a whole number of megabits, e.g. Thanks for the detailed explanation! I reimplemented the algo in python, and it matches with snes9x's output (with the small number of roms I've tested so far). We mirror this resulting 4MBit part, creating a 8MBit part, which combined with the existing 8MBit part creates the 16MBit part we need to end up with 32MBit. We mirror the 1MBit part, which then matches the 2MBit part, and thus have a 4MBit part. Use -f to remove that form of copy protection. Several games also check if they are running on a PAL or an NTSC SNES. We already have an 8MBit part, so we need to create another 8MBit from the rest. You can try -k to remove that protection. You take the largest part, then try to create another 16MBit part from the rest. So as you said for your 20MBit ROM you have one 16MBit part, then you take the remaining 4Mbit part and mirror this until you have another 16MBit part, and the end result is 32MBit.įor the 27MBit ROM you have one 16MBit part, one 8MBit part, one 2MBit part and one 1MBit part. By x200 byte header, I mean that when you open it in a hex editor, the first 512 addresses (512 bytes in decimal, 200 bytes in hex) are a header and not actual game code. These patches were made using clean ROMs as a base. (Which is the same as calculating the checksum recursively, which is what the function does) If you patched it and it's unclean, then it's a problem with the ROM you have. If you have multiple smaller parts you always mirror the smallest part first until it matches the next largest part, then mirror that whole group. Then the end result is also a power of two. For non power of two sizes the idea is to take the largest power of two block, then look at the remaining size in power of two parts, and mirror until you have another block of the largest size.

Snes9x bad checksum error fix