Guys please help, my asrock h81 pro btc arrived and i set it up with pci usb extenders and 6 750 ti , but windows is showing me only 5 cards , i cheked everything , changed slots , but nothing , the best i can get are 5 cards. Is there a driver issue or something else , i have a a friend who has the same board and puts 6 amd cards with no problem.?