cpu power "management" for non-dfs chips with no pmu (for instance, 750cxe and mpc7447 in pegasos)

[Matt Sealey]

Is there any support for using the ICTC to reduce CPU power and so on
for PowerPC currently, in absense of a real PMU like on Macs, or the
dual-PLL/DFS/DFS4 stuff in newer G3 and G4 chips?

I was wondering if there were any definitive performance benchmarks
to see if the setting had any appreciable effect in the first place.
If it doesn't do much more than kill a couple of milliwatts and the
switch between ICTC settings has too high a latency, it would make
no sense in a desktop system.

I am basically trying to evaluate if we can do ANYTHING to reduce
power consumption of systems which are idle, as I have noticed that
for running firmware (sitting at a Forth prompt) and booting a
Linux kernel and doing some work (for instance a simple benchmark),
power consumption barely changes at all. The difference between an
idle G4 and a running G4 is negligible. RC5 makes a big difference
but it is heavily tuned. Most people won't run RC5 all the time to
stress the CPU to the level that it wants to draw a couple extra
watts, I think.

Comments? :)

-- 
Matt Sealey <matt at genesi-usa.com>
Manager, Genesi, Developer Relations