I have an, what I would call if it were happening to someone else, interesting problem
My computer contains:
Z77 Pro3 motherboard
i5-3570 CPU (Ivy bridge)
Gigabyte 7870 OC 2GB videocard
and I run Windows 7 64-bit.
There is more stuff connected to my PC of course, but nothing relevant.
The problem is that the card, which is a PCIe 3.0 card, does not run in the PCIe 3.0 slot. The BIOS does not even see it.
When I plug it in the PCIe 2.0 slot it is detected by the BIOS and it runs.
If I plug my friend's 4800 (or smthg) in there it is detected by the BIOS and runs.
I have the latest BIOS intalled and my Gigabyte drivers are up to date (although that should not impact it not being detected by the BIOS).
I can not disable the IGPU, I can only choose a preference setting for the primary display, which are: On-board, PCI Express and PCI.
This motherboard did not work with my 6870. It would not POST with 6870 if you did any change in overclock related change in BIOS.
Setting PCIe2 to "Gen 1" would cause computer to boot but Graphic card would not be recognized by Catalyst drivers or they would claim that is does not work right