GA Z77X-D3H PCI-E Bus problem

[graberrr]

Hi, I've been struggling with this issue for a some time. My PCI-E x16 bus is working in x2 mode. Since my second x16 bus  is working in x8 mode I know something is up with the first bus. I tried everything - full reinstall of OS, changing settings in BIOS ( unfortunately there's no option to switch the bus to x16). Does anyone have any ideas? Or should I get new mobo? Thanks

[shadowsports]

Greetings,
A few questions.

What vid card in in the top slot? (Gen 2 or 3)
Are you seeing x2 in its properties or how are you measuring the speed of the slot?
What happens to the top x16 slot if you remove the card currently in slot 2 running at x8?
What is the card you have installed in the second slot?
Are any other expansion cards installed?

Specs do state that the top PCIEX16 slot will operate at up to x8 mode when slot 2 is populated...  but you should still get solid x8 performance in most cases.  Look for a BIOS setting (Video) with Auto, Gen2 or Gen3 option and see if changing between these modes helps. It might just be the brand or type of the second card.  Let us know.