Just go MACcing!
Hi Bo, there's NO PROBLEM running games on a MAC PRO 3.1! See my signature for more details. For the video card I used a EVGA GTX 670 FTW 4GB :thumbup:, this can be a PC VERSION (full driver support in MAC OS X 10.8.2) no matter what.
I used (2x) MAC mini PCIe to PCIe PC Y-splitter cable's and cross-wired both my NVIDIA GT8800 MAC-EDITION and the EVGA GTX 670 FTW PC VERSION for maximum logic-board PCIe power balancing!
These cables are both connected to the onboard PCIe power connectors: See image below
https://www.dropbox.com/s/2357wpm1g20vv0k/Onboard_PCIe.jpg
http://www.moddiy.com/products/Appl...Dual-PCIe-6%2dPin-Video-Card-Power-Cable.html
Hook-up your monitor to the EVGA and keep your ATI-MAC edition with a (added) simple TFT monitor for bootscreen and/or admin tweaks!
Screenoptions in MAC OS X 10.8.2.
https://www.dropbox.com/s/3mpdg6w172oa51y/BOOTCAMP 5_0.jpg
Output EVGA OC Scanner X 2.2.2
2013/01/19 @ 20:12:55 >> Detecting GPUs...
2013/01/19 @ 20:12:55 >> Found 2 GPUs.
2013/01/19 @ 20:12:55 >> - GPU 1: NVIDIA GeForce 8800 GT
2013/01/19 @ 20:12:55 >> - Bus ID: 1
2013/01/19 @ 20:12:55 >> - Cores: 112
2013/01/19 @ 20:12:55 >> - Partitions: 4
2013/01/19 @ 20:12:55 >> - Shader Pipes: 7
2013/01/19 @ 20:12:55 >> - Memory size: 0MB
2013/01/19 @ 20:12:55 >> - Memory type: GDDR3
2013/01/19 @ 20:12:55 >> - Bios: 62.92.20.00.16
2013/01/19 @ 20:12:55 >> - GPU temperature: 67.000°C
2013/01/19 @ 20:12:55 >> - Graphics driver:
2013/01/19 @ 20:12:55 >> - True clocks - GPU clock: 300MHz - Memory clock: 100MHz - Shader clock: 0MHz - GPU voltage: 0.000V
2013/01/19 @ 20:12:55 >> - PState 0 - GPU clock: 600MHz - Memory clock: 900MHz - Shader clock: 0MHz - GPU voltage: 1.050V
2013/01/19 @ 20:12:55 >> - PState 12 - GPU clock: 300MHz - Memory clock: 100MHz - Shader clock: 0MHz - GPU voltage: 0.950V
2013/01/19 @ 20:12:55 >> - Fan speed: 30%
2013/01/19 @ 20:12:55 >> - Fan speed: -1 RPM
2013/01/19 @ 20:12:55 >> - GPU 2: NVIDIA GeForce GTX 670
2013/01/19 @ 20:12:55 >> - Bus ID: 2
2013/01/19 @ 20:12:55 >> - Cores: 1344
2013/01/19 @ 20:12:55 >> - Partitions: 4
2013/01/19 @ 20:12:55 >> - Shader Pipes: 4
2013/01/19 @ 20:12:55 >> - Memory size: 4096MB
2013/01/19 @ 20:12:55 >> - Memory type: GDDR5
2013/01/19 @ 20:12:55 >> - Bios: 80.04.4b.00.70
2013/01/19 @ 20:12:55 >> - GPU temperature: 68.000°C
2013/01/19 @ 20:12:55 >> - Graphics driver: 9.18.13.1090
2013/01/19 @ 20:12:55 >> - True clocks - GPU clock: 1005MHz - Memory clock: 3004MHz - Shader clock: 0MHz - GPU voltage: 0.000V
2013/01/19 @ 20:12:55 >> - GTX 600 series - GPU base clock: 1006MHz - GPU boost clock: 1084MHz
2013/01/19 @ 20:12:55 >> - PState 0 - GPU clock: 1293MHz - Memory clock: 3004MHz - Shader clock: 0MHz - GPU voltage: 0.988V
2013/01/19 @ 20:12:55 >> - PState 2 - GPU clock: 1293MHz - Memory clock: 3004MHz - Shader clock: 0MHz - GPU voltage: 0.988V
2013/01/19 @ 20:12:55 >> - PState 5 - GPU clock: 862MHz - Memory clock: 810MHz - Shader clock: 0MHz - GPU voltage: 0.988V
2013/01/19 @ 20:12:55 >> - PState 8 - GPU clock: 324MHz - Memory clock: 324MHz - Shader clock: 0MHz - GPU voltage: 0.988V
2013/01/19 @ 20:12:55 >> - Fan speed: 46%
2013/01/19 @ 20:12:55 >> - Fan speed: 1890 RPM
2013/01/19 @ 20:12:55 >> GPU monitoring thread started up ok.
2013/01/19 @ 20:13:47 >> Freeing EVGA OC Scanner X resources...
2013/01/19 @ 20:13:47 >> Exit from EVGA OC Scanner X.
EVGA installed in Slot-1, NVIDIA MAC installed in Slot-2
NVIDIA GT8800:
1x PCIe 6-pin from onboard connector #1
EVGA GTX 670 FTW:
1x PCIe 6-pin from onboard connector #1
1x PCIe 6-pin from onboard connector #2
1x PCIe 6-pin from onboard connector #SPARE
https://www.dropbox.com/s/r8zuz3eda249mem/EVGA_GTX670_FTW_PC_in_MACPRO.jpg
RED: indicates a non-compatibility issue within Windows using the scanner on the NVIDIA GT8800 MAC_EDITION!
Goodluck mate and cheers on your choise to use your MAC!!!! RUNS LIKE A HOT KNIFE THRU BUTTER! ;-)