I've got a strange problem. I bought my old/new PC:
AsRock P67 Pro3
i5 2550K
2x 4GB A-DATA 1600CL9

It's everything ok when I'm using my old GPU - HD5770 or GTS250, but if I try to use VTX3D HD7950 X-Edition Boost v2 it's calling D6 error "missing VGA". I've got 2 similar models of this card and both I checked in other PC and 100% working.

What I tried to do:
- update BIOS 3.1 => 3.3
- powered from MOLEX
- drivers (but it's obvious not working cause i cant see nothing including UEFI and POST screen).

And now can someone tell me what is going on? Is it missing microcode in BIOS of motherboard or in GPU (it cant change mode from PCI-e 3.0 to 2.0?)? P67/CPU isnt compatible with PCIe 3.0 but i see even newer cards working on it. Or maybe CPU is broken? I dont have ane ideas what can i do with it. Can you help me?

PS. Sorry for my english :(

Thx for help :)