They're for updating the microcode. That is tangential to their use AIUI, but useful. Also AIUI the microcode controls the issuing of the micro-ops. > It woul

They're for updating the microcode. That is tangential to their use AIUI, but useful. Also AIUI the microcode controls the issuing of the micro-ops. > It would be way too slow to make that programmable Then what is the "processor microcode updates" updating? I think this may just be a terminology mixup. Dunno if this helps, FYI from https://stackoverflow.com/questions/17395557/observing-stale-instruction-fetching-on-x86-with-self-modifying-code/18388700#18388700 https://stackoverflow.com/questions/17395557/observing-stale... ...and I can't copy/paste it. In the above link, look for 'embarrassing' by Krazy Glew.