mike wrote:

Exactly what is microcode in this context?

Recent intel processors don't natively execute x86 or x86_64
instructions that compilers or humans produce, they use a lower level
internal microcoded instruction set. So to a limited degree they can
issue new microcode (which the CPU will only accept if it recognises a
signature on it) that alters how the processor actually runs.

It appears that there's a new class of microcode that can directly
change persistent code within the microprocessor itself???

No intel CPU microcode needs to be loaded into the CPU at every reboot
(by the BIOS, or by the O/S)

all this really any big deal? If it ain't broke...

You don't regard meltdown and/or spectre as evidence of breakage?