What does this mean?

DragonZero · Post by **DragonZero** » Wed Nov 03, 2004 11:40 pm

When I load a certain game it says at the bottome CHSUM: Failed
What does this mean exactly?

Paul Bunyan · Post by **Paul Bunyan** » Wed Nov 03, 2004 11:46 pm

you have a bad ROM, or you patched said ROM

Post by **grinvader** » Thu Nov 04, 2004 1:32 am

The calculated checksum of the rom you load is different from what is written in the rom itself.

As Paul mentioned, this means your rom is either a bad dump or patched. Some bad dumps may work perfectly, but we don't care about bugs happening with these.

DragonZero · Post by **DragonZero** » Wed Nov 10, 2004 8:29 am

ya i patched it. but i also patched another game it doesn't say this. i don't think the rom is bad because i tried it on three different roms from different places. anyway what i really want to know is does this chsum:failed do anything to the content of the game? or the gameplay itself?

snkcube · Post by **snkcube** » Wed Nov 10, 2004 8:37 am

I think when games have a checksum fail, they can have random freezing or graphical glitches.

Post by **grinvader** » Wed Nov 10, 2004 10:21 am

Some (relatively) old patches correct the checksum of the rom along in the patching process. This is not exactly good, because we'd like to keep the checksums as a real indicator of the status of a ROM. And a patched ROM, even if it's for translation purposes, is NOT a good dump.

We'd like to have good checksum == good dump... but many hackers modified the internal checksum so that some roms pass the test, despite being bad dumps.
That's why some people have made NSRT.

As long as the original rom (unpatched) is fine, and you patched it correctly, then it's normal for the checksum test to fail.

If the original rom doesn't have a good checksum, you *might* experience a lot of graphical/sound bugs, even freezes, and you won't be able to report them, as its a problem with the rom, and not with the emu.

So, in brief...

Unpatched ROM
- checksum OK: good
- checksum FAIL: not good
You shouldn't patch over a bad checksum rom, as usually the creators of the patch designed it for a good dump.

Patched good ROM
- whatever checksum: good
Because some patches mess the checksum (it's normal) and some others correct it (they shouldn't, but the game will work.)