PCIe slots not functioning correctly.

w1ntervention · 23 Mar 2016 at 17:09

Hi guys, constructed my first computer about a year ago, and noticed that the only some of the PCIe slots were working correctly. However, since I was only using one graphics card, I did not give it the attention I should have, but now I wish to use multiple cards and may have a problem.

I am using the asus x99s motherboard, and an evga gtx 970 GPU.

The 1st PCIe slot operates fine, using all 16 lanes.

However, when I take the same graphics card out and put it in the second x16 PCIe slot, and boot the computer, it never connects to the monitor at all.
When I put the same graphics card in the third x16 PCIe slot, according to GPU-Z it only ever utilizes 1 of the lanes (even with the render test).
When I put the same graphics card in the fourth PCIe slot, according to GPU-Z it only ever utilizes 8 of the lanes (even with the render test).

Is this because of a fault motherboard, or is it a less costly problem?

Cheers.

stulid · 23 Mar 2016 at 22:07

What CPU do you have?

w1ntervention · 24 Mar 2016 at 01:46

intel i7 5820k

Armadillo · 24 Mar 2016 at 17:00

With a 5820k, I would check the manual for the board, see how the slots work out. On my board for example (GA-x99-sli), the second x16 slot is only x8, regardless of the population of the other slots, when a 5820k is being used.

Could be something similar on your board.

Other than that, checked the cpu socket for bent pins?

w1ntervention · 25 Mar 2016 at 11:29

The manual advises to use the first slot with a single GPU.
Using two GPUs it advises to use the first slot (x16), and the fourth slot (x8).
Using three GPUs it advises to use the first (x16), second (x8) and fourth (x8).
Does this mean that the fourth slot for example, will only ever operate at x8, even if only one GPU is being used? If so I guess that would explain why the third slot only operates at x1 too as it is not meant to be used with a 28 lane CPU.