Test 6 Failing Only for CPU 5

[syndac]

I just build a new PC:

i5-8500 (used)
2x16GB 3000mHz CL16 RAM (new)
ASRock Z390M Pro4 Mobo (new)

And I cant get it to install an OS; it crashes immediately upon trying to load the installer from a boot menu. I swapped out some known good RAM and ran into the same issue.

So, I ran Memtest86 (on the unknown RAM--have not tested the known good RAM) and tests 1-5 all seem to pass just fine. However, test 6 fails only for Core 5 with so many errors it won't continue. If I disable Core 5 in the BIOS, test 6 passes just fine. Is this a CPU issue?

If you need me to run more tests or additional information, please let me know.

[David (PassMark)]

BIOS really allows you to disable just Core 5 ?

Would be could to double check with known good RAM.

RAM errors are more common that CPU errors. But if errors are the same with both sets of RAM, the yes, maybe the CPU is bad.

[syndac]

BIOS really allows you to disable just Core 5 ?

Would be could to double check with known good RAM.

RAM errors are more common that CPU errors. But if errors are the same with both sets of RAM, the yes, maybe the CPU is bad.

It doesn't allow me to specify which core, but it lets me select to use any number of them. With Core 5 being the last and selecting 5 (of the 6) cores in the BIOS, it appears to leave out the right one. I also manually selected Core 5 in Memtest.

I just swapped for my good RAM and experienced the exact same results...tests fine until Test 6. There was also 2 errors for Core 5 on Test 7 and then enough errors to abort the tests on Test 8.

Thinking it's the CPU, then? Could it be the Mobo? Which do you think would be more likely?

[David (PassMark)]

More likely CPU if errors are just on one core, and also appear with multiple different sets of RAM.

[syndac]

Got a new CPU and have confirmed that the CPU was defective. Thanks for all the help!