I know there is a thread on this - but i have other questions. Please excuse me for not knowing very much about Mac Pros im semi new to the OSX/ Mac world, my questions might not make total sense. Right now my friend has a 2006 Mac Pro 1.1 (Two 3.0ghz Dual core), and its got a 8800GT. He wants to upgrade to a HD5870, so here are my questions. 1.) Is it possible - at all - to get the PC version of the HD5870 to work in a Mac Pro? Can you just plug it right in, or does it need 'flashed'? If so, will it work in both OSX and Windows? 2.) Whats the difference between a Apple HD5870 and a XFX/MSI/Gigabte 5870? And, they say the HD5870 cards will work with 2006-2008 Mac Pros, but they say Apple doesn't officially support it...what does that mean...they block it from working?