I just picked up 3 video cards from eBay. They were advertised as good used cards. I bought 7950's Saphire Edition. The first one has a fan that spins really loud and then loses picture in about 30 seconds. The second one loses picture in about 15 seconds. The third one seems to work for about 5-10 minutes and then shuts off. Is it possible because these are PC video cards that I am having issues. I realize there won't be any boot screen, but I'm wondering if all of the video cards are busted, or if they just don't play well in my 2009 Mac Pro on Yosemite for some reason. A 5770 and a GT120 both work perfectly in the Mac.