u/TheRealG0nz0-_-

Hi, I’m trying to diagnose an intermittent hard-restart issue with my PC. I’m at the point where I think possibly either the PSU, CPU, or motherboard is the issue, but I’d much appreciate some other opinions before I start buying and testing new hardware.
My specs:
• Ryzen 9 7950X
• RTX 4090 24GB
• ASUS PRIME X670E-PRO WIFI
• ASUS ROG Strix 1000W Gold PSU
• 32GB (2x16GB) Corsair Vengeance RGB DDR5-6000
• Samsung 990 Pro SSD
• Corsair iCUE Link H150i LCD 360mm AIO
• Windows 11

The problem:
My PC will randomly hard-reset while gaming. It’s not normally a crash-to-desktop or BSOD. The display goes black and the whole PC restarts.
It originally happened occasionally in games like EAFC 26 and Battlefield 6, but has now also happened in heavily modded Skyrim and Spider-Man 2. BF6 is particularly reproducible and can crash the PC while loading into a game. Spider-Man 2 has sometimes crashed immediately on launch, although other times I can play for quite a while. The games never freeze or lag, the PC just straight crashes.
Windows generally only records Kernel-Power Event 41 + volmgr Event 161. There is no BSOD/dump, and Reliability Monitor generally only says Windows was not properly shut down.
Earlier in troubleshooting I discovered a large number of WHEA-Logger Event 19 errors. The ones I checked consistently reported:
Reported by component: Processor Core
Error Source: Corrected Machine Check
Error Type: Cache Hierarchy Error
Processor APIC ID: 0
One example had MCABank 13 and MciStat 0x9c2040000602010b.
However, I haven’t had another WHEA event for several days, despite the PC continuing to hard-reset while gaming. The recent crashes only produce Kernel-Power 41/volmgr 161.

Troubleshooting I’ve done:
Updated motherboard BIOS to latest version
Updated AMD chipset drivers
Loaded BIOS Optimized Defaults
Disabled DOCP and tested RAM at stock settings
MemTest86 overnight with DOCP actually enabled — passed
OCCT CPU test ~45 min — 0 errors, max CPU temp ~85°C
OCCT targeted Core 0 test — passed, no WHEA generated during test
OCCT GPU test — passed
OCCT combined Power test — passed
Tested with a completely different 2x16GB DDR5-6000 kit in A2/B2 at stock settings — PC still crashes
Cleaned NVIDIA drivers with DDU in Safe Mode and installed fresh Game Ready driver — still crashes
Reset NVIDIA settings to defaults
Reduced RTX 4090 power limit to 60% using MSI Afterburner — still crashes
Tried disabling Global C-State Control — didn’t fix it
Checked/reseated motherboard 24-pin, CPU EPS, GPU power and PSU-side modular connections
Temperatures appear normal

Another potentially important symptom:
It hasn’t happened for a while but on several occasions after shutting the PC down normally and returning later, pressing the case power button has done absolutely nothing. The motherboard RGB remains illuminated, so it has standby power, but the PC won’t start.
Switching the PSU off, waiting, switching it back on and then pressing the power button allows the PC to boot normally.
This makes me suspicious of the PSU or motherboard, although the repeated APIC ID 0 Cache Hierarchy WHEAs obviously make the CPU suspicious as well.
The system can also pass CPU/GPU/combined loads and then hard-reset almost immediately when launching a game, which is what’s confusing me.

My current thoughts:
I’m considering RMAing the ASUS ROG Strix 1000W PSU first because it’s still under its long warranty, but I don’t want to blindly replace components.
Given all of the above, would you suspect:
• PSU
• Ryzen 9 7950X
• Motherboard/VRM/power delivery
• RTX 4090
or something else?

Any help would be greatly appreciated 🙏🏻