5V vs 3.3V PCI is not about power supply but about
signal levels. A 3.3V only, non 5V tolerant card will either not work or be destroyed in a 5V slot. The other way around, a 5V card in a 3.3V board can destroy the board and other cards inserted.
Usually the notches prevent anything incompatible from being inserted - 5V cards have the notch away from the bracket, 3.3V cards on the bracket side and universals both. All Amiga PCI boards are 5V, so you'll need 5V (very old) or universal cards.
All TNT2 M64 PCI cards I could find on the 'net are either 5V or universal - but: I can remember having trouble with an M64 in an old Pentium board of mine (Asus T2P4) due to it being not PCI 2.
1 compliant.
