Updates can be stored in the BIOS flash, so if you can program this you could theoretically update the microcode. The OS can also patch the microcode during boo

Updates can be stored in the BIOS flash, so if you can program this you could theoretically update the microcode. The OS can also patch the microcode during boot. The signature/encryption is still a problem, which might be why they are using older AMD K8 and K10 processors from 2007 which didn't have this security. Still, if the keys do leak out of AMD or Intel, this is a huge security hole.