Most of the ISA may be implemented in microcode, but the parts that matter are certainly not microcoded! For example the TLB access and the fast path of the TL

Most of the ISA may be implemented in microcode, but the parts that matter are certainly not microcoded! For example the TLB access and the fast path of the TLB miss are not microcoded. You only get to microcode if you have to set an accessed bit or a dirty bit, or if there is a page fault.