QUOTE (WideEyedFox @ Sep 28 2009, 06:04 PM)

Interface on the motherboard supporting PCI Express 2.0, and either DDR2 800 or DDR3 1066 RAM

Apple says Compatibility:
Requires Mac Pro (Early 2009 with 1066MHz DDR3 memory) or Mac Pro (Early 2008 with 800MHz DDR2 FB-DIMM memory) with PCI Express 2.0 slot
Mac OS X v10.5.7 or later