I've tested with Cinebench R20, Blender Benchmark, Windows 10 Memory Diagnostic, memtest86 v.8.2 (Passmark UEFI version), 3DMark (demo version from Steam), Unigine Heaven and Valley benchmarks. All OK (meaning no errors, nor crashes).
First thing I would recommend is to test with default RAM settings until you get your temp problem diagnosed. Shoot for XMP later.
But in Prime95 (Version 29.8 build 6) I get rounding errors almost right away. Usually for Worker 4 and 3.
That is not good. At stock with the stock cooler, the CPU should be able to select an appropriate voltage and clockspeed setting to get Prime95 stable out-of-the-box. My 3900x (for example) downclocks and undervolts pretty aggressively in this workload, even with massive cooling. My current "default" settings (I tweaked LLC and other stuff) runs Prime95 SmallFFTs at 1.104-1.128v vcore with a temp of 58C. It sits at around 3900 MHz running this bench. That's only 100 MHz higher than the advertised "base" clock. And under older AGESA versions with different LLC settings, it wouldn't even run that well. AMD has improved the Prime95 performance of this chip considerably with microcode updates.
If I disable AVX2 and AVX, I do not get this error. But I only let it run for about 10 minutes at a time, because the CPU temperature gets to about 90 degrees in this case.
90C with no AVX?!?!?
Disabling the memory XMP profile does not help with Prime95.
Glad you tried that. For now, i would recommend leaving XMP disabled anyway. One thing at a time.
I tried then the second available BIOS 7C02v31 (v.3.1, with 1.0.0.3AB). No change in Prime95.
I would stick with the ABBA UEFI variant, despite the problems the mobo OEM had in properly updating their product's UEFI. Bleh.
The Prime95 rounding error does not seem to be caused by my RAM, but I don't have any other DDR4 to test with (I only have some DDR3 modules).
I would highly recommend sticking to the SmallFFTs test (if you are not already) since it does not stress RAM.
Could it be because the stock cooler is not adequate for this Prime95 task?
Possibly. Might be a bad mount.
Also possible, but less probable than a bad mount or the stock cooler being crap.
Hard to say for sure, but you could run memtest86 to help eliminate RAM errors. If you have 4 passes no errors, it is likely the CPU.
Only Blend and Large FFTs even test RAM. Blend also produces much lower temps than SmallFFTs, so I suspect that he's running SmallFFTs anyway.
The error appears almost right away (under a minute). Almost always worker 3 or 4 fails first.
What it means is you're hitting an unstable clockspeed/voltage combo right off the bat. I have a plan to deal with that. In fact, let's try it now.
Go into the UEFI. Make sure LLC settings are OFF, or at whatever setting corresponds to OFF (LLC 0). In my UEFI it is LLC "Standard". LLC "Auto" does . . . odd things, and I do not recommend it. Again, make sure LLC is off! Then set a negative voltage offset of -.1v in the UEFI. Do not set a static offset. Leave everything else stock. Then start rerunning your applications. Watch temps and clockspeeds, and compare to what you got with everything bone stock. I think you'll be pleased, but I could be wrong. Also be sure to compare benchmark results between runs! For example, compare your CBR20 score before and after the LLC/offset tweak. If the score gets lower with the tweak, then we may be seeing clock stretching, which means the offset is too aggressive.
In Cinebench R20 (during the multithread test) the CPU temperature gets to about 82 Celsius.
It shouldn't get that hot. Though I've heard of the stock cooler letting the CPU get up around 80C while running Blender for awhile, so . . . anyway, try the tweaks I recommended, see if that helps.