Running under Linux Ubuntu 18.04 with standard/default BLAS library I observe normal behavior. If I install a parallelized BLAS library such as MKL or openblas, any simple matrix operation causes the machine to shut down and reboot immediately. Behavior occurs on a System76 Thelio desktop with Intel i9 9900K processor, and confirmed observed by System76's own technicians. Behavior does not occur on comparable AMD processor in the same machine.
To reproduce from a fresh ubuntu 18.04 install: If I install python3, numpy, and MKL (e.g. following http://dirk.eddelbuettel.com/blog/2018/04/15/) and try some parallel matrix algebra, e.g. on Python following http://hduongtrong.github.io/2016/03/07/Matrix-Multiplication-Benchmark/, the machine crashes/reboots. Identical behavior occurs doing the an parallel matrix algebra in R, so is not software-specific.
As best as I can tell, this seems to be due to the Intel i9 9900K itself when running parallelized BLAS (including but not limited to MKL), but I am unsure how to properly document and report this issue. Any suggestions would be appreciated.