Intel Skylake/Kaby Lake processors: broken hyper-threading

Probably.. The remarkable thing here is that Intel's internal randomised testing wasn't able to uncover this in the last two years. Usually once a major CPU is produced in silicon there is extensive randomised A/B testing performed on instruction sequences to look for variations relative to the golden architectural model, so this must be a remarkably unlikely combination of things if testing of two generations of CPU failed to uncover it.. Often this kind of testing finds all kinds of crazy and unlikely stuff.

The truth is new CPU architectures are usually pretty buggy in the first couple of steppings. The are full of disable bits and configuration stuff that the CPU vendor recommends to the BIOS to setup..