>>>>> "Len" == Len Brown writes:
 >> I have done some measurements on a Toshiba S7/290LNKW, which has a
 >> 900MHz Pentium-M. The results have been posted to this list a while
 >> ago -- the most surprising one being that the Pentium-M in that
 >> machine seemed to always consume the same amount of power when idle,
 >> independent of operating frequency.  The frequency only made a
 >> difference when the CPU was actually doing something (or when I made
 >> it not use the C3 state by loading usb-uhci).

 Len> Probably the cpu is running HLT in the idle loop, so the power
 Len> consumption there would not vary with MHz.

Oh -- well, that's exactly what I wanted to check. It seems it does vary
for speedstepped Pentium-III Mobile, according to my measurements,
that's why I was surprised.

This should influence the design of dynamic power management -- if the
CPU is already idle, there is no point in slowing it down. It only makes
sense to change the frequency when we're actually doing something.

--J.