PowerNowd uses the CPUFreq sysfs interface to set the frequency of the processor depending on the system's current condition. I run PowerNowd on my backend (AMD64 3700+) and whenever the machine is idle the machine runs at 1000MHz which is a 7 degree reduction from when it's running at full speed. PowerNowd was designed to work with AMD's PowerNow technology. AMD's Cool-N-Quiet technology coupled with PowerNowd creates the perfect solution for a cool and quiet solution.
By default PowerNowd will not adjust its frequency settings for `nice` programs so your transcode jobs will run much slower. I'd recommend starting PowerNowd with the following:
That will start the daemon in quiet mode plus take `nice` programs into consideration. Please visit PowerNowd's website to read documentation and download.