Not long after AMD released the first Ryzen processors to market a few weeks ago, a strange bug involving FMA3 instructions (an extension to 128-bit and 256-bit SIMD instructions that performs fused multiply-add floating point math operations) was discovered. If you were to trip over this bug yourself, its effects would have been impossible

Source: Hot Hardware – AMD Preps Ryzen EFI BIOS Update To Fix Dreaded FMA3 Code System Lock-Ups