What is the Mac equivalent of Windows' Power Plans' Maximum Processor State? One of my favorite features in Windows is the built-in Power Plans. I can change how much energy my computer uses - whether I want it to drain power like there's no tomorrow and get incredible performance or whether I want it to run like a turtle and use 1% CPU at the max and barely use any power, or anything in between. 

My favorite feature of Power Plans is that I can limit CPU usage. I can make it 30% - or 72% - or 94 percent.

On a Mac, I notice that there are no Power Plans. There is this, but that doesn't do it.

What can I use to limit CPU usage by the entire system (not just one process) on a Mac?
OS X has SpeedStep built in, but as you have noticed you have no/little control over it.

Coolbook is a program that works on pre-Lion versions of OS X but is still not working correctly under Lion?  It is also limited to Core Duo and Core 2 Duo processors.