Pcie slot 1 only 8x?

[CoolMan]

Lo.
I just got an asus rampage v extreme and i'm having issues with the first pcie slot. It will only run at 8x instead of 16x.

I'm running an intel 5960x cpu with 2 780ti's in slot 1 (pcie_x16_1) and slot 4 (pcie_x16/x8_3) as per the manual.
However the bios says the card in slot 1 is detected, but running at 8x native, but the card in slot 4 runs at 16x.
All power including the ez plug are connected.
And if i run uniengine benchmark it says that the card in slot 1 is only at 324Mhz where the card in slot 4 runs at full speed and my scores are way down because of it.

Even using the dip switch to disable all slots except slot 1 and bios still says only 8x even with all sata drives etc disconnected to avoid sharing.
Any idea on what could be wrong?

[samboy87]

to be honest , i dont think its your RVE mobo. What BIOS are you using now? and have you updated to the lastest ''1502''?
have you tried Load Default Bios settings?
Have you checked all cables? what PSU do you use? have you tried another 8/6pins powercable? and check that it's in the right socket on the PSU.
and have you tried with 1 card and not in SLI.
do you have an M.2 or other PCI-E card installed? if so. try to take it out and only try 1 GPU in the first PCI-E socket.
If you have an Air duster! take out your GPU and clean the connectors and the PCI-E Socket! its enough to have an dust partical in your PCI-E slot!
Check NB PCI-E configuration and force to Gen3.
and are you 100% sure all pins are ok on your CPU?
Cant you try with a newer GPU? 980/970?

try all steps and let us know.

[CoolMan]

already tested all of that and more, 4 different bios, only tested with the single card installed. tried various gpu's etc even gave the mobo to a friend for testing in his rig and same issue with his amd cards.