Intel has disclosed that its sixth-generation Core products (known as Skylake) suffer from a CPU bug that can cause a system to hang. The company has only publicly identified one application family that causes it, Prime95.
The Prime95 thread on Skylake instability dates back to early December, when testers noted that running the 768K test on the latest Intel processors would cause the application to fail — sometimes within minutes, sometimes only after hours. The forum users collectively worked through the usual suspects and double-checked RAM, motherboard vendors, voltage levels, clock speeds, Prime95 software versions, and whether the CPU was overclocked or not.
Disabling Hyper-Threading apparently fixes the problem (based on user reports), but none of the other variables had a measurable impact on the issue. If you run Prime95 on a Skylake CPU with the maximum number of threads available on the processor with the “CpuSupportsFMA3=0” (which forces the use of AVX) at the 768 FFT size, the system will eventually crash.
Unfortunately, Intel’s current disclosure is vague at best. The complete statement reads: