It astounds me that CPUs can be patched. Can anyone comment on how that works?
Some instructions (legacy or more complex instructions, especially the ones you'd find in OS code) are implemented by microcode, and that microcode can be patched.
Microcode also plays a role during CPU initialization, which is when configuration registers are set (which may disable some functionality that turns out to be buggy). Or, as in this case, in power management.