For years, Intel’s compiler, math library MKL and their profiler, VTune, really only worked well with their own CPUs. There was in fact code that decreased performance if it detected a non-Intel CPU in place:
That later became part of a larger lawsuit, but since Intel is not discriminating against AMD directly, but rather against all other non-Intel CPUs, the result of the lawsuit was underwhelming. In fact, it’s still a problem today:
Given that the MKL is a widely used library, people also indirectly suffer from this if they buy an AMD CPU and utilize software that links against that library.
As someone working in low-level optimization, that was/is a shitty situation. I still bought an AMD CPU after the latest fiasco a couple of weeks ago.