Honestly, the best resources I know are the ISA/architecture manuals directly from each vendor (Intel, AMD, Arm) for the various CPUs and/or GPUs of interest. P

Honestly, the best resources I know are the ISA/architecture manuals directly from each vendor (Intel, AMD, Arm) for the various CPUs and/or GPUs of interest. Prior to that, my experience largely comes from doing (working with lower level code, benchmarks, looking at assembly, profiling hardware counters, etc.).