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CRCs - Stop Wasting Your Time.


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Over recent weeks I've been receiving more and more messages from folks about roms matching the CRCs we have in databases. I never mind helping people get setup, but I think there are some points that need clarifying here...

A CRC (as we use them) is a code generated by performing a calculation on a file. If two files are exactly the same, as in they are a bit for bit match, the CRC code will be the same for these files.

We add CRCs to game list databases to aid the process of matching game roms to the entries in the database. Note that these are to aid the process, and they should be used as such. They particularly help when matching large sets, as they can help slim down the need for manual matching.

Note this very important point...

(I think I've typed this some 100 times in recent weeks)

It is possible to have two game roms which are exactly the same game, that have different CRCs.

Let me say that again...

It is possible to have two game roms which are exactly the same game, that have different CRCs.

A third time??

It is possible to have two game roms which are exactly the same game...

 

Why is this?

Possible for a bunch of reasons, but it happens because for whatever reason, the arrangement of bits that make up the game rom file is different.

That could be because the roms were dumped using different techniques, maybe the 'header' is actually at the end of the file, or maybe the game is a translation and it's been patched differently. Whatever the reason, remember the key point -

It is possible to have two game roms which are exactly the same game, that have different CRCs.

In short - if the name and region matches - you're good to go. If the CRC matches too, well great. But it really, really, really doesn't matter. You'll still have the same game.

 

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