Question Random resets and pre-POST restart loop

Sep 9, 2021
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My brother has some wierd issue with his PC. I will list the specs first then explain the issue.

Rog strix z370-f
I5 8600k
2x8gb forza 3200mhz
ssd evo 950
Gtx 1070
RM650x
Corsair h115i Pro (cpu aio)

It started once when he tried to turn on the pc. Started to restart loop every 3 seconds before making it to POST. We Performed a bios reset and it worked.

Next day the same thing but this time CMOS didn't help. Managed to boot it up on the integrated only. Tested his gpu(1070) on my PC and it runs fine. Tested with my PSU on his PC and same results. Gpu on - reset loop/ gpu out - works.

Took everything out of the PC and re assembled on the table. It worked. I was suspecting the aluminium heatsink that sits in the bottom right of the motherboard (rog strix z370-f) was colliding with the gpu and because of that it was not sitting well in the PCI-E. Well I took it off and reassembled everything else.

It worked for 3 weeks when problems came again. Removed the gpu and used only the on board for the past week. When he told me that even with on-board he is getting random resets but without the boot loop.

  • Checked his temps and they never get past 62c.
  • Checked event viewer and nothing suspicious. - - - Only the loss of power error.
  • psu is ruled out because is only 6 months old and testing my own rm750 does the same symptoms
  • gpu works fine on other PC
I'm suspecting a faulty mobo.

What suggestions do you have guys?
 
prime95 reboots hmm
unstable cpu overclock can cause reboot
mainboard vrm hitting cap can cause reboot
PSU could be culprit aswell (doesnt matter if its 6months old, manufacturing errors can happen and pass QC)
check you power outlet if it doesnt fluctuate when stressing your PC
 
Sep 9, 2021
6
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10
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prime95 reboots hmm
unstable cpu overclock can cause reboot
mainboard vrm hitting cap can cause reboot
PSU could be culprit aswell (doesnt matter if its 6months old, manufacturing errors can happen and pass QC)
check you power outlet if it doesnt fluctuate when stressing your PC
Cpu runs on stock frequency. It never goes past 65c even in prime stress
Symptoms appear with the other PSU aswell (rm750) which I use in the other pc with no problems and it runs a ryzen 5600x and rtx 3080
 
without cpu overclock, u wont be hittin mobo vrm cap, so you can rule that out
power outlet you can check with multimeter
otherwise if all ok, then CPU has issue, check for bent pins on mainboard and burnt marks on cpu (this will also rule out reseating cpu cooler)
 
Sep 9, 2021
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Not suspecting motherboard at all? Why would cpu do a reset loop with the gpu plugged in and with on-board starts normal but with random resets?
 
Sep 9, 2021
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Removed the CPU today and spotted 4 bent pins

3 on the center right side, respectively on the diagram DMI_TXN (0), a empty pin and PCI_BKLKP

And one on the center below the middle gap, one of the VCC

Tried getting them back in position with some sewing needle and phone zoom but still doesn't work with GPU plugged in. I suspect that they move around from the right position when the CPU Is sloted.

I have ordered another Motherboard, MSI MPG plus z390. Will come with an update once it arrives.
 

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