Hi guys, I can say I successfully installed two ATI 4870 (Apple + Diamond) on my 2006 Mac Pro. I installed that Power Supply in the second CD ROM. It worked but installing it was a pain in the a**. When I first installed the Apple 4870 I had to remove that black metal frame to make it physical fit. Then it's straight forward working on Mac and Windows Vista. The I opened up my Mac Pro installed the Power Supply and Diamond ATI 4870. It worked and I didn't believe it it worked on Mac and Windows Vista. Yeah you heard me right it worked on Mac. I installed the crossfire jumper but it didn't work. THAT'S my problem. I don't know why but the Catalyst Center doesn't give me the option for crossfire. I tried uninstalling then safe mode then use drive cleaner removed everything then restarted installed the Drivers restarted. NEVER worked. Guys with the Mac Pro and crossfire experience. Please share your wisdom!