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Author Topic: Using RHDN/Reverse Searching for a ROM used by a Hack  (Read 409 times)

the_mez

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Using RHDN/Reverse Searching for a ROM used by a Hack
« on: July 18, 2020, 12:16:21 am »
I'm trying to figure out if it's possible to use RHDN to basically reverse-search for a rom used by the creator of a hack. Specifically, the Zero Playable rom used for Mega Man X2, as the original X rom was very specific, while the one for X2 is just (USA) and therefore I could get the wrong file and keep getting "bad checksum" errors.

Any help at all with this is greatly appreciated.
« Last Edit: July 18, 2020, 12:57:25 am by the_mez »

KingMike

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Re: Using RHDN/Reverse Searching for a ROM used by a Hack
« Reply #1 on: July 18, 2020, 02:05:07 am »
I don't think that will be of use.
The only ROM information we store is the ROM Information provided by the user. We only have patches, which contain the data modified by the user. We don't keep full ROM data.

For SNES games, make sure the ROM is in the correct Headered or Unheadered state. That is the most common patching issues. "Bad Checksum" is normal because ROM hackers rarely modify the ROM to fix the checksum.
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FAST6191

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Re: Using RHDN/Reverse Searching for a ROM used by a Hack
« Reply #2 on: July 18, 2020, 11:06:48 am »
Assuming it isn't just the checksum thing mentioned by KingMike then so you found a prepatched ROM and would like the original used for it.

Your best bet would be to see if you can assemble a collection of all the various ROMS out there (goodtools tends to collect those if you want a list to compare checksums against, most others tend to go for the purest example), see what unique data they might have in them and see if that matches the patched ROM. For later systems the header included with the ROM tells you a lot about what it is in but on older ones then less data tends to be included.
If it is a popular game (and megaman/rockman tends to be) then all the various versions will probably be listed and known to speedrunner types and possibly collectors in general which could also help narrow things down.

Bonus here is you can dodge the header thing if you make sure the prepatched one is without it and all the ones you are comparing it against or generating a patch for are headerless (or you can go the other way and make sure everything has a header -- everything just needs to be the same in that regard).