HardOCP reports motherboard makers have received new AMD AGESA microcode for the Ryzen processor and that new UEFI files are appearing on the support pages of motherboard maker's websites. I checked a couple of motherboards but couldn't immediately find evidence of new files. The website also offers some word of advice about upgrading UEFI as they're under the impression that a lot of users have put off building new PCs for quite some time, and UEFI upgrades work a little different than old BIOS flashes:
And as always, we suggest flashing the UEFI from inside the UEFI, not inside your OS. Also keep in mind that these newer UEFI do not always flash like older BIOS. I suggest flashing UEFI from a USB flash drive. Leave the flash drive in the system and leave it alone until you see the system back to the desktop, or back in the UEFI with instructions on what to do. The trick here is to NOT remove the new UEFI files until you are 100% sure the system is finished with the files. It is not unusual for this to take a "long time" with these newer UEFI systems, and it is very likely that you will encounter some reboots during this process.
At the moment, it's not clear what the purpose is of this AGESA microcode update. Better DDR4 memory support is a highly anticipated update but from what we've heard that update was still some time away.
Another possibility is that it fixes the recently discovered FMA3 errata. Users discovered that programs that execute FMA3 instructions can completely crash the entire Ryzen system, and not just the program or virtual machine that executes the command. This is not supposed to happen and poses a potential security risk, so it's good that this flaw was discovered before the rollout of the Naples server platform. I'll provide an update when there's more certainty about this microcode update.