Description:

The microcode_ctl utility is a companion to the x86 microcode driver.
The utility has two uses: a) it decodes and sends new microcode to the
kernel driver to be uploaded to Intel IA32 or AMD64 family processors.
(Pentium Pro, PII, Celeron, PIII, Xeon Pentium 4 etc.) b) it signals
the kernel driver to release any buffers it may hold.

The microcode update is volatile and needs to be uploaded on each
system boot i.e. it doesn't reflash your cpu permanently, reboot and
it reverts back to the old microcode.