Microcode updates are encrypted, and only Intel has the key. There are exploits to extract the key, but otherwise you're pretty much locked out. I don't know

Microcode updates are encrypted, and only Intel has the key. There are exploits to extract the key, but otherwise you're pretty much locked out. I don't know a whole lot about microarchitecture, but from my understanding, it's not possible to modify microcode's actual uOps in software, it's the translation from assembly to microcode that's being patched in updates.