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Motherboard problem? Asrock Z370 PRO4 PCIE port issue

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xboxgamer:
PC specs:

MB Asrock Z370 Pro4
CPU: Intel 8700k
GPU: MSI 1070TI

I suspect I have problem with my motherboard.

MB was working perfectly fine since I bought it in 2018 up until a month ago when the problems started. First I would get frequent blue screens with crashed video driver (nvlddmkm.sys).

By trial and error I determined that when I change the PCIE slot from x16 to x4 for my GPU, PC becomes much more stable. I can sometimes work whole day without BSOD but still occasionally I get the BSOD like 2 days ago where I was working on project in GNS3 whole night and suddenly PC crashed and I lost all my work. Moreover now booting up my PC is a big lottery, 4/5 times I press power on button I can hear fans spinning but no light on keyboard, no monitor no mouse, i then have to restart it 5 times and then eventually it will boot and work like described before, sometimes whole day, sometimes couple of hours without crash.

Steps I try to resolve: took out whole MB out, cleaned from any dust but there was almost none, cleaned PCIe slot inside with brush, re-seated RAM, tried to boot single RAM stick in all banks, still the same, re-flashed BIOS.
Took out CPU and cleaned it, not problem with MB pins or CPU discoloration. Checked whole MB for any bulged or leaked capacitors.  I checked diode reading of all diodes next to PCIE x16 slot, all pairs had the same reading.

I then found EVGA KB article how to check voltages on each cables from PSU, created a jumper and I checked every single cable in PSU going either to GPU or CPU and 24 pin plug. All had voltages within specs (3.3V, 5V, 12V).

Also I tried to put GPU back to PCIE x16 slot and PC booted up normally but when I opened GPU-Z I saw that PCIE speed is reported sometimes as x4, sometimes even x1. Occasionally it will show x16 but after some time it will still crash.

All this makes me believe that there is a motherboard problem. I haven't tried putting my GPU into another motherboard because I don't have one yet. I already ordered another MB from Aliexpress (same model) but decided to ask if anybody knows what could be the issue.

Could this be something easily fixable? Or chipset problem and not a chance to fix without reballing? One thing that comes to my mind is maybe VRM unstable voltage but I am not that advanced so I might need help to find the cause here.

Please throw some ideas what to check and I will follow your guidance. Thanks

indeterminate:
You can chk out the voltages on the bus but i suspect that the problem is not there.
https://en.wikipedia.org/wiki/PCI_Express

It sounds more like an intermittent fault " solder joint , cracked resister etc " with a clock line or data lane.
you could chk if one of the termination resisters in Lane 0 reads differently to lane 1 , 2 etc see the wiki page.

how data is sent over the pcie bus
https://ww1.microchip.com/downloads/en/DeviceDoc/PCIE%20Express.pdf
this is very difficult stuff to debug without sum fancy test gear

xboxgamer:
Update:

My replacement motherboard from Aliexpress just arrived and unless the MB from Ali is also faulty in the same way (I say fairly unlikely) then it's not a MB issue because it acts exactly the same way. Still Card is shown as Pcie x4 in x16 slot and already my PC hanged once during booting up.
 
This leads me to believe it's a GPU issue. I already took my 1070TI apart and I can't spot anything obvious.

Except that all VRM's show dead short to ground but I think this should be normal.

wraper:
Why don't you run it with no graphics card inserted? 8700k has igpu after all.

xboxgamer:

--- Quote from: wraper on September 14, 2024, 02:23:57 am ---Why don't you run it with no graphics card inserted? 8700k has igpu after all.

--- End quote ---

I actually do right now  :)

But my intention is to fix the GPU hopefully.

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