Geforce 9800 GT Running On Early Mac Pro (EFI32)
http://discussions.apple.com/message.jspa?messageID=8988306#8988306
To make a long story short, I now have a 9800 GT running safely on my early Mac Pro.
It is a single GPU solution and it works reliably under both Mac OS X and Boot Camp Vista Ultimate 32 and is the fastest GPU (according to the Open GL benchmarks) I've ever seen on any Mac Pro. Absolutely no artifacts under either environment and the Crysis series is easily handled in Boot Camp. Still testing though...
Here is the specific GPU that's now installed:
http://www.newegg.com/Product/Product.aspx?Item=N82E16814187026
The dual fans make it insanely cool. It's also quiet and while perhaps a useless observation, its setup of copper heat sinks and connectors, etc., appears very practically done while also being a kind of attractive arrangement as well.
My 9800 GT is a reflashed PC board by bruinmacs:
http://shop.ebay.com/merchant/bruinmacsW0QQ_nkwZQQ_armrsZ1QQ_fromZQQmdoZ
As for installation to replace my also very fast 8800 GTS, I had to remove the side rail (two screws) and the daughter board (small lcd display) from the standard 9800 GT so it could fit in the lowest slot. The small lcd is not helpful for us Mac Pro owners.
I don't know for sure, but I believe this board by bruinmacs will run in any Mac Pro (it is PCIE 2).
FYI...
Cheers,
tyvol
2007 Mac Pro, 2 x 3 GHz Quad-Core Intel Xeon, Mac OS X (10.5.6), GPU=GeForce 9800GT 512 (PC board reflashed), 1 Raptor (150GB), 3 Seagate (750 GB)