ROM Hack Question about how to manually find Game ID

[twiztidsinz]

I know that you can just open up R4CCE and choose to add the ROM as a new game and find it out, but I'm interested in being able to manually find it for myself.


Example:New Super Mario Bros (U)
A2DE 77DAD131

Open the ROM in a hex editor and you'll see right at the top: (spaces and 00's displayed as _ for visual aesthetics)

4E 45 57 20 4D 41 52 49 || N E W _ M A R I
4F 00 00 00 41 32 44 45 || O _ _ _ A 2 D E

This gives you the 4 "main" Game ID characters.

Get the first 512 (0x200) bytes of the file [0x00000000 - 0x000001FF]
Calculate the CRC32
Do a bitwise NOT (or substract the CRC32 from 0xFFFFFFFF)

 

[twiztidsinz]

http://nocash.emubase.de/gbatek.htm#dscart...tactionreplayds
ABCD-NNNNNNNN Game ID ;ASCII Gamecode [00Ch] and CRC32 across [0..1FFh]


I'm not sure what the [00Ch] and [0..1FFh] mean...
The "00Ch" looks like 'address 00C in "h"ex', and C (13th spot in) is where the first 4 of the Game ID is.
So that would mean that from 0 to 1FF would be the part CRC32'd. I tried pasting it into a new fie, but the CRC still doesn't match.

 

[blow_fly98]

I just discovered it. If you use HexWorkshop, there's a dropbox containg "None", "1s compliment" and "2s compliment". Select "1s compliment" and you get the right CRC32.