I have one 7850 graphic card installed in the pcie 3.0 x16 slot of the motherboard (z77 pro3)
Mobo only detects the card if the option Gen1 is selected in BIOS configuration and obviously the speed of the bus is 1.1 all the time (checked with GPU-Z)

In AUTO mode or gen3 mode the card is not detected but in gen2 selection something curious happens. The card is detected but not the units connected to SATA ports, so the system can't boot.

Last BIOS version running in the system.

Any ideas?

Thanks and sorry for my english.