After spending days trying to figure out why I was getting occasional and random performance problems and weird CPU issues, I finally stumbled upon that (virtual) core 2 (7900x) was basically sitting at almost 100% in the Resource Monitor. This was completely random. I might have to restart the machine 20 times to get it to happen.
I went through the normal troubleshooting, defaulting bios (0802), disabling turbo, tested ram, removed all the ram but 1 stick, swapped that single stick out between different sticks, temps are all legit when stress testing, etc. No Luck. I build 20-30 systems a year, so not new at this!
I ordered another motherboard and video card. removed all the other peripherals, except the hard drive. swapped everything out. I eventually got a repro. I got another CPU in (7820x this time), eventually got another repro. At this point everything has been swapped out but the case, PSU, and HD.
On a whim, I flashed the bios back to 0503. So far I have not been able to reproduce the problem. Other than the restarting-shutdown issues I had experienced previously on the 0503 bios, it seems to be running fine.
I have been looking around and have not seen any reports of this. I just seem to see reports of more random issues. Does anyone have any experience, weird, issues or information on this?
Intel 7900x/7820x
Asus Prime x299 A (2 of them)
Noctua NH D15
Nvidia 750GT (2 of them) (also tested an older 640)
Corsair DDR4 2400 4x8GB (C14)
Corsair RM 850x
Samsung 850 evo's