Ok, well I downloaded a nifty new software program today that basically functions like the "Cool n' Quiet" feature of the A64, but it lets you configure the multiplier and voltage settings, along with timings for how long before upstepping, downstepping, etc.

For those unfamiliar with CnQ, basically it lets your CPU run at a very low speed (500mhz in my case) for nearly all operations, but will dynamically increase clockspeed as the percentage of CPU load goes up. So.. for example if my CPU spends more than 500ms above 90% load at 500mhz, it will jump to full speed (2075Mhz) and hold that until it spends at least 5 seconds averaging less than 10% load, at which point it will drop back to 1250Mhz, and if it still stays below 10% load for another 1 second, it will fall back to 500mhz again.

So long as your motherboard supports software control of the multiplier (and optionally voltage) you can use it on K6, K7, A64, and Pentium M boards. Here's a full review of it:

http://www.silentpcreview.com/article231-page1.html