This may be buried in the FAQ, so I thought I'd give it it's own thread. It would have been useful when I was searching for this information. If not, I am sure the mods will delete it. I thought I would let everyone know that MSI Twin Frozr GEFORCE GTX 660 OC Edition works in Slot 1 with 1 6-pin power plugged on a Mac Pro 3,1 with Mac OS X 10.9.4. Works fine with either native drivers or NVIDIA web drivers. Latest CUDA drivers installed. I tried the PowerColor Radeon HD7850 with the Kext edits and it did not work for me.