CRC verified roms not verifying

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CRC verified roms not verifying

Post by littlewierdo »

So this is really strange, RC is reporting some Asia NES roms I have using the no-Intro dat files as unknown. But whats really odd is, the crc checksum is the same as what RC is looking for (at the top under the 'red' games, I looked at what RC is looking for, then I went down to the bottom where the unknown roms are and the checksums are exactly the same).

What makes this even stranger is that the file size RC is seeing is different than the expected file size which has me puzzled.

How can the checksum be the same but the file sizes differing by as much as 3k (according to RC)? Ill whip out my calculator and figure out what they should be in bytes later tonight and see if RC is maybe misreporting the file sizes.

I mean, I understand the checksum will rarely come out to be the same when you have different files but this should be an extremely rare occasion and I have 5 roms (could be more but I dont feel like visually verifying all 66 of the roms RC doesnt recognize) where the checksum in my roms matches the expected checksum.

Has anyone else noticed RC not recognizing roms with a matching checksum to what its expecting (I saw a post just below mine with screenies that appeared to be the same problem Im having).

Its very troubling cause Im trying to put together this set and Ive been working on this for the last 2 months and it turns out that I may have been wasting alot of time because my original set is probably perfect...:(

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Re: CRC verified roms not verifying

Post by Hakkk »

Well in fact, CRC32 is not a strong checksum algorithm. It is not that hard to make a fake or watermarked rom with same CRC32 checksum. An example is that many ISO images released by Microsoft all have CRC32 0xFFFFFFFF. That is why the MD5 or SHA1 checksum should also be introduced into the ROM verification.

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Re: CRC verified roms not verifying

Post by money_114 »

Nes crc checksum is the same but size is the Different
Because rc don't use header

For clrmamepro, you have to enable the NES header functionality. Settings->headers (path combobox).

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Re: CRC verified roms not verifying

Post by RomCenter »


I have tested with the new nes dat (for RC) downloaded here
This nes dat uses the nes plugin (check in 'about/plugin' tab if the plugin is 'nes.dll').

The nes plugin analyses the file to find if a header is included and remove it. If no header is found, or the size of the file is a correct nes game size, it does nothing more than calculating the file crc. The size sent by the plugin is the size of the file without the header and it should match the no-intro dat sizes.

The no-intro dats provide crc of headerless roms (no-intro pure rom files).
Eric - RomCenter developer
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