Controlling CPU Clock

Taking out the battery on the new ones lowers the cpu speed, and there's a utility called coolbook that some people use to lower cpu speed and voltage.

I do not use nor do I endorse either of these methods of cpu adjustment, this kind of thing is use at your own risk as far as I'm concerned. Good luck.

I don't think energy saver does anything to your cpu, I'm fairly sure it just controls backlight, display timer, hard drive timer, and sleep timer.

 

I don't quite understand why you would want to lower the speed manually (unless you are bothered by the fans? But I personally don't find the fans loud at all when idle).

If you have an Intel MBP, the Core 2 Duo processors have Intel SpeedStep technology, which means whenever your CPU isn't doing intensive work (idling at desktop or a website), it is automatically down clocked, and its voltage is lowered. This is built-in to the CPU itself and you don't have to do anything at all. Of course as soon as you launch some CPU intensive application the CPU will be back to its full speed. Hope this helps.