I am facing a weird problem with the Mac Pro which I am using. I have two 4870 cards installed on the computer. The problem which I am facing is the Mac Pro does not boot when the two 4870 cards are connected. The operating system installed on the computer is Snow leopard. Can anybody here explain me why my MacPro with two 4870 cards does not boot? Any help regarding the topic are welcome. Is this because of some hardware failure? Please help.