NVIDIA GeForce 7800 Buying Guide
These PC GeForce 7800 GS AGP 256MB 256bit GDDR3 cards can be flashed to Mac version using the suitable ROM available in the WikiDownloads. These cards work perfectly in G5 Power Macs (AGP) They should also work fine in G4 Power Macs with AGP 4x slot (Digital Audio, Quicksilver 2001, Quicksilver 2002, MDD, Firewire 800) once you disable pins 3 & 11.
This ROM ONLY works with cards that have the BIOS Revision: 5.70.xxx.xxx. (this is usually written on a sticker on the backside of the card)
The BIOS Revision number indicates the GPU model used on the card. 5.70.xxx.xxx means the card has G70 GPU - original GeForce 7800 GPU. Newer cards use the same PCB but a different GPU - G71 which is original GeForce 7900 GPU (BIOS Revision number is 5.71.xxx.xxx). The card's commercial name still remains GeForce 7800 GS but these newer cards are actually GeForce 7900. NVIDIA had to rethink the ROM CODE structure for G71 and newer GPU, that's why it would need a very different MAC ROM to work.
If you have a 7800 card that does not match any of these, and none of the existing 7800 ROMs work for you, you can build your own Mac ROM using information from your card's PC ROM only if you have the 5.70 BIOS. Information for doing this is available here: NV Fcode ROM Editing Preliminaries.
These cards used the ROM without any modification:
-BFG 7800gs oc.
Same cards different heatsink.
Here is a package to provide full OpenGL support for flashed GeForce 7800 GS AGP for Mac OS X 10.4.9, using GeForce 7800 GT OpenGL Engine :
Just follow instructions from the "Read Me First" file within the uncompressed folder.