How free actually PBP is ?

[Der Geist der Maschine]

cpu microcodes

Every month someone asks this question, but nobody ever worried about microcode.

What's wrong with microcode driven instruction execution? I gained the impression that this is awesome on architectures which let you replace the microcode to fix subtile bugs. That's not possible on hard-wired instruction execution, is it?

You can get either non-free microcode or non-free hard-wired instruction execution circuitry. Does it matter?

Do you worry about backdoors? I assume it's veeeeeeeeery difficult to put backdoors in microcode so that 1) a full-fledged OS actually boots to completion while 2) making some programs exploitable by a microcode induced backdoors.

Now PBP needs some kind of open firmware to be even more flexible.

Some firmware lies in the ROM internal to the SOC. That can't be replaced. Where do you see inflexibility in the current firmware?