On original PS1 hardware, the full unlock code can cause a Memory Card error if you have more than 300 cards already. Use this on a fresh save file for best results.
If you see silver boxes:
D433C060 00000FFF C433C060 00000FFF
Most GameShark versions require a "Master Code" (Enable Code) to run. D0056634 1021 80056636 2400 yugioh forbidden memories gameshark codes verified
Have a code we missed that you have verified yourself? Share it in the comments below. Keep dueling, Pharaohs. On original PS1 hardware, the full unlock code