I have a Dell D800, which has the Intel Centrino chipset with the Pentium-M cpu. I'm also running Win XP which has support for managing the speed of the CPU via built in speedstep technology.

Too bad it sucks. The speedstep magic happens via the Power Management control panel. There are a bunch of power management schemes that you can choose from… but you can't tell what they are really doing. I was getting pissed that during compiles my computer was loafing along at 600mhz even while on AC. I changed the profile a few times and got it to go up, only to have it fallback.

So the first thing I found on Dell's website is a patch for Win XP to resolve some speedstep issues. Great. Except according to a Dell employee on their forum, once you've had the problem it's too late. Some settings get incorrectly set in the registry, and the patch doesn't fix that. Well that's just great. After some experimentation, I think this only means that the Dell supplied power management schemes are buggered as my system does the right thing once I figured out the default schemes.

That's where a Microsoft white paper titled Windows Native Processor Performance Control comes in handy. It explains the various settings that are in play behind the schemes:

None= full power
Adaptive=speed up or down depending on load
Degrade=low speed or worse depending on availible battery.

Power Scheme AC Power DC Power
Home/Office Desk None Adaptive
Portable/Laptop Adaptive Adaptive
Presentation Adaptive Degrade
Always On None None
Minimal Power Management Adaptive Adaptive
Max Battery Adaptive /td>

Degrade

That still doesn't give me the kind of control I want, but at least I can see how the schemes differ.

Then I found SpeedSwitchXP an excellent GPL'd utility that allows you to see/modify all the settings behind the various power schemes. Sweet.

It does exactly what I wanted. That was when I noticed I had a crashed mozilla in the background (stupid Flash plugin) that was pegging the CPU at 100%. No wonder why the fan was running so much.