Depending on how microcode is defined, it's arguably existed back to the 40s. Which modern and reasonably performant CPUs are you thinking of that don't have microcode?

You completely misunderstood my comment.

What were you referring to, other than microcode?

Edit: Oh, you mention the encryption. Big companies love obfuscating everything they create, because they're afraid something commercially sensitive will exist there and someone will copy it and outcompete them. I agree that this is ridiculous, but I don't think it's evidence of any sort of nefarious activity.

It's not evidence, but it may well have been used to hide such evidence.

Well yes anything that's encrypted could potentially turn out to be evidence of a crime when decrypted, but we don't usually assume that the use of encryption is indicative of that

For criminal cases. But this is not.

Yes, because large corporations never commit criminal infractions, or admit any wrongdoing. They just happen to settle with regulators as cost of doing business.

Microcode spills lots of the secrets of the hardware design, so you want it encrypted for as many years as possible to keep your trade secrets out of competitors’ hands.

They were always going to need microcode to deal with errata or are you referring to encrypting the microcode rather than just signing it?

The latter. I can see why they did it but if it was used to hide something nefarious Intel is done.

If they have to hide something, it will not be in the microcode. They always expected it to be broken one day. If it is on the die it will take a massive effort to be found and understood, if ever. And it is actually much easier to hide from the employees as if it was in the microcode, many of them could have extracted the keys and sold them to a foreign power.

What whole thing? Instruction microcoding is nothing new.

Or do you mean.

- the TXE vulnerability and / or undocumented debugging mode (so microcode wouldn’t have been extracted)

- microcode encryption so the microcode would always have been completely readable

- x86

- Intel itself

?

The second, possibly combined with something dirty.

I can see why they would sign/encrypt it so that things got safer, but then they should have done a much better job of it. If it was encrypted to hide something that could not stand the light of day then that's an entirely different matter altogether.

Time will tell.

At what point in time did encrypting microcode in processors become common? Is this a relatively recent practice?

IIRC, it happened when IME was introduced. Maybe 2008?

Then AMD PSP did the same starting in 2013.