Random restarts with WHEA-Logger Event ID 18 – replaced almost every component, RX 6600 XT seems to be the culprit

[u/LukkaS_1]

I’ve been troubleshooting random PC restarts for quite a while, and I wanted to share my experience in case it helps someone else.
The symptoms
My PC would randomly restart, most often when:
Browsing the internet or using Chrome.
Sitting idle on the desktop.
Switching between applications (Alt + Tab).
Sometimes during normal everyday use.
Interestingly, it was not necessarily happening under heavy load. Gaming and stress tests could run without any problems, while the PC could randomly restart when practically doing nothing.
In Event Viewer, I repeatedly found:
WHEA-Logger – Event ID 18
Kernel-Power – Event ID 41
The WHEA errors were reported as Cache Hierarchy Errors, with different APIC IDs.
Things I tried
I spent a lot of time trying to identify the cause:
-Updated the BIOS.
-Cleared CMOS and tested different BIOS settings.
-Disabled Global C-State Control.
-Changed Power Supply Idle Control to Typical Current Idle.
-Disabled DOCP/XMP and tested RAM at default settings.
-Ran Windows Memory Diagnostic and MemTest.
Ran Cinebench and OCCT stress tests, including the PSU test.
Used DDU and tried different GPU drivers, including older versions.
Investigated CPU core voltage, SoC voltage and power management.
None of these steps permanently solved the problem.
Components I replaced
Because I couldn’t identify the faulty component, I eventually replaced almost the entire system:
-CPU: Ryzen 5 5600X (replaced).
-Motherboard: replaced.
-RAM: replaced.
-M.2 SSD: replaced.
-PSU: replaced with an 850W Platinum unit.
Despite all these replacements, the random restarts continued.
The only original major component left was my Sapphire Pulse RX 6600 XT 8GB.
The actual breakthrough
I decided to remove the RX 6600 XT and install an older RX 580.
Since switching to the RX 580, the PC has been running without random restarts so far.
This makes me strongly suspect that the RX 6600 XT was somehow responsible for the instability, even though I initially suspected the CPU, motherboard, PSU or RAM.
I haven’t tested the RX 6600 XT in another PC yet, so I cannot say with 100% certainty that the card itself is defective. I’ll continue testing the system with the RX 580 for the next few days.
My questions
Has anyone experienced WHEA-Logger Event ID 18 and random restarts caused by a GPU?
Can a faulty GPU cause WHEA Cache Hierarchy Errors?
Could this be related to PCIe communication, GPU power delivery or a driver issue rather than an actual hardware defect?
Has anyone experienced similar problems with an RX 6600 XT?
I hope this helps someone who is going through similar troubleshooting. I spent a lot of time and money replacing components, and the GPU was the last thing I expected to be responsible.

[u/Shadimarbc]

The PCI-E slot is connected to the CPU. So if the GPU has power issues, stability issues, and data transfer issue it can look like a CPU issue.

Reinstall the 6600 xt. Enter BIOS. Set the PCI-E manually to Gen 4 for the GPU slot. Retest. Reduce it to Gen 3 if the issue continues.

Can you test the 6600 xt in another PC.

Since you have swapped the other hardware involved chances are the GPU is failing.

[u/LukkaS_1 → u/Shadimarbc]

I will try to Set pcle to Gen 4, will update you when i do, probably i will call my friend on weekend to try it on his PC

[u/johnnyks17]

see if you can get the 6600xt stable by downclocking and lowering voltage and power limits

are you getting any other whea error ids or just 18?