An AMD Ryzen 7-1800X powered machine was found to be crashing upon execution of a very specific set of FMA3 instructions by Flops version 2, a simple open-source CPU benchmark by Alexander “Mystical” Yee. ‘
An important point to note here is that this little known benchmark has been tailored by its developer to be highly specific to the CPU micro-architecture, with separate binaries for each major x64 architecture (eg: Bulldozer, Sandy Bridge, Haswell, Skylake, etc.), and as such the GitHub repository does not have a “Zen” specific binary.
Members of the HWBot forums found that Ryzen powered machines crash on running the Haswell-specific binary, at “Single-Precision – 128-bit FMA3 – Fused Multiply Add.” The Haswell-specific binary (along with, we imagine, Skylake), adds support for the FMA3 instruction-set, which Ryzen supports, and which lends some importance to the discovery of this bug.
What also makes this important is because a simple application, running at user privileges (i.e. lacking special super-user/admin privileges), has the ability to crash the machine. Such a code could even be executed through virtual machines, and poses a security issue, with implications for AMD’s upcoming “Naples” enterprise processor launch.
[Source]
