The legacy "1st Generation" GeForce 8800 GT brings much desired improvement to 3D acceleration for the 2006/2007 Mac Pro series. It's not quite as fast as the version we tested in the "early 2008" Mac Pro but that's likely due to differences in architecture including memory speed, frontside bus speed, and core frequencies. At $279, the price is reasonable.
It's a shame Apple could not produce a GeForce 8800 GT that works in all models of Mac Pro. You'll notice we were able to boot and test the ATI Radeon X1900 XT and HD 2600 XT in both models of Mac Pro. That's because ATI included a big enough ROM to hold both EFI 32 bit and 64 bit code. Why Apple didn't do that for the GeForce 8800 GT is a mystery to me.
Though the addition of the GeForce 8800 GT is a step forward, one only has to look "over the fence" at the GPUs available to Windows PC users to wonder why we can't "have it all and have it now." I'm referring to the Geforce 9800 GX2 and Radeon HD 3870 X2 we tested recently under Vista 64.
MAKING THE RADEON X1900 XT WORK
Some reports have come in that the Radeon X1900 XT does not work on their "2008" Mac Pro. We have had no problems running it in our 2008 Mac Pro 3.2GHz. We asked ATI about this issue. They suggest performing the firmware update on the Radeon X1900 XT while it is installed in a 2006 or 2007 Mac Pro. Then moving it to the 2008 Mac Pro.
NOTE: We can NOT get the Radeon X1900 XT to boot Vista 64 from our Boot Camp partition. We are forced to use the Radeon HD 2600 XT (or GeForce 8800 GT) for that purpose.