Not really honestly. I mean, I thought the microcode update is done by the firmware and/or the OS on boot. Assuming that's correct, whether it's performed or not is entirely dictated by those entities... not by anything related to the CPU. It's like saying "I'm moving to New York" just because there's a car that drives you there from New Jersey every day. And if you really want to call that 'persistent', I'm not sure how one might have a non-persistent update in that case?