Question Problem with PCIe Slots

[dforrest]

I am have having problems with my PCIe slots. A few days ago, without warning, my system stopped recognizing the graphics card in the X16 slot. The computer would not boot up. The fan was intermittently running and the EVGA logo was not lit (later the fan stopped running completely). I moved my graphics card to the X8 slot and it works in there with no problems. I have temporarily returned it to the X16 slot and the problem with this remains. I would obviously like to use the card in the X16 slat.

Can someone please help?

My system details are:
GTX 1070 graphics card
Windows 10 Home 64-bit
Intel Core i5 @ 3.60GHz
Motherboard Gigabyte Technology Co. Ltd. Z370XP SLI-CF
RAM 16.0GB Dual-Channel
1863GB TOSHIBA DT01ACA200 hard drive
476GB ADATA SX7000NP SSD
Power supply EVGA 650W G2 GOLD

 

[Eximo]

Check the slot for damage or debris. Re-seat the CPU in the socket.

 

[dforrest]

Check the slot for damage or debris. Re-seat the CPU in the socket.

Thanks Eximo but I have tried all of this and the problem remains.

 

[Eximo]

You took the CPU out of the socket?

 

[dforrest]

Yes, I have it in the X8 socket where it is working with no problems.

 

[Eximo]

You are misunderstanding. PCIe slot, CPU socket. The CPU not the GPU. The pins on the bottom of the CPU connect to the PCIe slots. Not a common problem, but it worth trying before you toss the motherboard, or anything else.

I understand that the 8x slot is working. You want the x16 slot to work and there are only five things involved, the CPU, the GPU, the slot, the socket, and the motherboard.

CPU has 16x PCIe lanes connected through the motherboard pins. The motherboard has traces going from the CPU socket to two of the slots. 16x lanes to the primary slot and 8x lanes to the secondary slot.

With the GPU working in the 8x slot, we know that the CPU pins for the first half of the x16 slot are working, and those 8 lanes of traces on the motherboard are working, and the GPUs first half of the PCIe pins are working.

What we don't know is if the GPU has an issue with its remaining PCIe lanes, or the CPU, or the Motherboard.

Easiest test would be to drop your GPU into another computer, that would verify the GPU has all its pads and traces working.

Motherboards and CPUs pretty much have to be tested together, so you would need a known good motherboard to swap the CPU into to see if it is the board or the CPU.

So, one quick thing you can do is take the CPU out, and put it right back in. Give the motherboard pins a good visual look, and check the bottom of the CPU for any damage or corrosion.

 

[dforrest]

Thanks but I think you are mistyping GPU and CPU in your reply. The CPU (central processing unit) is plugged into the motherboard. The PCIe slot is part of the motherboard and the GPU/graphics card plugs into this.

On my motherboard I have X16, X8 and X4 slots. All three are of the same length and pin configuration. The GPU can physically be plugged into any of them but there is obviously a different speed when the X8 is used instead of the X16, due to the lesser number of lanes.

I am retired and living on a small Caribbean island and do not have access to the resources you will have.

 

[Eximo]

I am telling you to remove the Central Processing Unit and check it. I laid out in great detail my troubleshooting thought process, if that doesn't make sense I suggest taking the system to a computer repair shop. They will be able to verify the graphics card works in another x16 slot and CPU combo, even swap in a new CPU and see if that makes it work, if it does, that means the motherboard is damaged.

I've seen people pull CPUs before and found thermal compound on one of the CPU pads. Leaked AIO coolers, spilled soda, corrosion, bent pins, and straight up burn marks.

CPU provides 16x PCIe lanes directly to two of the x16 PCIe slots in the typical motherboard. The remaining PCIe slots are connected to the motherboard chipset, which itself connects to the CPU using DMI (itself a 4x PCIe lane connection). More recent Intel and AMD chips also offer PCIe lanes directly to an M.2 slot.

 

[dforrest]

I am still trying to diagnose and, if possible, resolve the issue using my system only. The strange thing is that my existing GPU does not work in the x16 slot but does work in the x8 slot. I have an old GPU and this does work in the x16 slot.