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Metroid Prime Savegame CRC [GameCube]

Started by MeganGrass, August 31, 2021, 04:25:34 PM

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I was curious about hacking this game's save files and was unable to find anything about it, except savestate hacking which I'm not aiming for. Soo.. I was able to create a quick bypass.

This AR code only works for v1.0 of the game and it simply Nop's the if/else branch if a mismatch is found. When active, you can save/load the game normally, and also load hacked GCI savegames without the game fussing about corruption and deleting the data.

$Bypass CRC Mismatch Error
0434ebd4 60000000

The actual CRC value calculation function appears to be located at 80315590, and it seems simple enough, but I can't find the proper value/s used to perform the bitwise operations. So, no tool for now.

Interestingly enough, it appears that the Trial/Demo version of Metroid Prime includes this exact same checksum algorithm; the function for that version is located at 8027260C. Maybe it's possible to force the Trial/Demo version to load save data..?

(For Slot A) The obtainable item bits start around 0x15CA and is about 0xC0 bytes. Visor opacity, brightness, etc is around 0x168A. The current suit is at 0x15D0, BE short, and accepted values appear to be 0-7.

Changing the starting location appears to be pretty tricky, and I haven't quite figured it out yet. I was able to change the save location from Tallon Overworld to Phendrana Drifts, but instead of starting at a save point, I was located at the entrance elevator.

Changing the visited areas:

...and a modified save file at the end of the game that will let you "peace out" on Ridley mid-fight and go straight to the Impact Crater: