Quote Originally Posted by Ughmahedhurtz View Post
The official site is https://www.mersenne.org/download/#download but that should work. It just exercises your CPU cores and RAM such that if you have bad memory or flaky devices due to poor power supply output or some other flaky hardware or a terrible heatsink setup, it'll fail the test and report an unexpected result. Or it'll BSOD. Or overheat. Watch it for 15 minutes or so and if the thermals don't climb past 65-70, it should be OK for longer tests.

Something to add to the power supply comment above is that if you stack a bunch of devices up on the same rail e.g. 4 HDDs on the same SATA cable bundle, etc. sometimes that will overload just that rail and the associated outputs. Your manual will usually describe which rails are common and how much they're rated for, though being a Dell, maybe not as I don't think those are modular.

The "common" thing also applies to PCI-E SSDs and SATA ports, depending on the motherboard. Some of my MB's SATA ports for example become unavailable when I connect a PCI-E SSD on one of the M.2 ports. This usually results in a simple failure to enumerate the affected SATA ports, but I can't speak to other shenanigans that might happen if you accidentally comingle those.

I am so glad this has gone in this direction! The PSU comments has led me to some testing and an important discovery indeed.

I believe inadequate power is the problem. This computer was purchased used as a less than adequate replacement for my main PC which was killed in a lightning strike back in early June. It'll be some time yet before I can truly invest in the hardware I need.

Anyway, the power supply was supposed to be 750W. It had a label saying 750W, but under that label is one that says 500W! So with some checking of the part numbers the top label goes to a completely different type. The rating for 12V is only 150W, obviously not enough for 95W CPU & 185W GPU. This would easily explain the insane behavior. Obviously I cannot further troubleshoot or test until I resolve this.

The system will be torn down as soon as I post this and I'll feed the wiring harness through the case and replace the power supply with my tested and working 875W unit.

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I just noticed your name, Ughmahedhurtz. I love it! It is something like I might have used as a chronic migraineur!

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Re CPU temps. You state "Watch it for 15 minutes or so and if the thermals don't climb past 65-70..." this makes me curious. My CPU, a XEON X5675, at idle is 33.4°C. During the testing or when I otherwise max all 12 logical cores at 100% it maxes out at 80.1°C. This didn't seem like a problem as the specs for the CPU state the max temp at the heat spreader to be 81.3°C. Am I mistaken in this? 80°C does seem hot but within spec, so I assumed it was fine. If not I will look for a better cooling option.