[throwaway2037]

Why is this downvoted? (At the time of writing, the text is grey, so it has at least a few downvotes.)

This is a good question. As others have noted below, yes, and sometimes you can see kernel logging on start-up when the microcode is loaded.

[wtallis]

It's a dumb question, because it's in reply to a comment that already implies the answer, and it's trivial to find an answer online in less time than it takes to post that question and wait for someone to supply an answer.

The subject of CPU microcode update mechanisms is an interesting and relevant topic, but such a shallow, low-effort question is not a good way to promote interesting discussion on that topic.