3900x and AVX workloads - instability
A curious one, this, but I am running my 3900x completely stock (in an X370 Taich), with Micron E-die at 3600C16 currently at 1.48v to try to exclude its part in the 'problems' I'm experiencing.
Basically, it fails Prime95 Small FFT with AVX enabled. Curiously, it will only run 3.8-3.9GHz all-core during this test, and the CPU doesn't go much above 70C. However, CPU voltages are also a measly 1.1v on each core. Small FFT AVX will fail within 10-20 minutes, usually on Worker 13. When I downclocked the RAM all the way to 2400c16, it would run longer, but I hadn't tested that longer than half an hour. There seems to be *some* dependency on the memory speed, but the curiosity here is that 9 out of 10 times, it's Worker 13 that fails first (so the 7th core).
When I disable AVX, the CPU boosts to 4.2GHz all-core at 1.2x-1.3x volts, and it runs an hour of Small FFT and just now ran an entire night of non-AVX blend, no problems.
Could this have something to do with too low a voltage at 3.9GHz? It seems that specifically for AVX workloads the CPU runs this frequency. And are there tables I can adjust to fix this?