There is no difference between a CPU rushing around in a tght loop
and exrecising a full blown compile.

There is some difference, as a tight loop won't lead to many state changes.
However, only very old operating systems run the CPU in the tight loop.
Almost all operating systems will put the CPU into idle if there are no
threads demanding execution, giving even greater power consumption drops.

The only thing that opoerartion affects is sometimes disc stepper
motors under high disc access. Otherwise a PC is a constant load
device, no matter what it is doing.

This hasn't been true for about 10 years.

Christian.