[chadgpt3]

Microcode in modern CPUs isn't anything like classic microcode - except for certain instructions like CPUID and WRMSR, where the CPU really does interpret a microcode subroutine.

It's become a generic term for patching parts of a CPU at startup time instead. Most of microcode is things like code for the Management Engine, chicken bits to disable features, routines for CPUID/etc, and yes, a small number of patch registers that can intercept execution of ordinary instructions and run microcode instead, but not enough to override all instructions accessing ah-dh.