PowerNowd

PowerNowd is a handy tool that connects to the CPUFreq driver. It works with Linux kernel versions 2.5 and 2.6 using the sysfs interface. To use this daemon, make sure you have a supported CPU and a kernel that’s sysfs compatible.

Understanding PowerNowd

The name might be a bit tricky because PowerNowd is not just for AMD's PowerNow! technology; it actually works with any CPUfreq capable processor. However, it shines best on processors that support more than two frequency steps, like those powered by AMD’s PowerNow! or newer Pentium M chips.

Tested Processors

This daemon has been tested successfully on various processors:

• AMD Mobile Duron 850MHz


• PowerPC G3 900MHz


• AMD K6-2+ 450MHz


• AMD Athlon64 3000+

I’ve even heard from users running it on:

• SMP Intel P4-m (with speedstep and hyperthreading)


• Intel P3


• Intel Pentium-M

How to Run PowerNowd

If you’re ready to get started, just type this command as root:

powernowd

Your Options with PowerNowd

You’ve got some cool options to play around with:

• -h: Displays help message.


• -d: Keeps it attached to your terminal (default runs in the background).


• -v: Increases output verbosity—you can use it multiple times.


• -q: Quiet mode for emergency outputs only.


• -m #: Choose modes of operation (0 = SINE, 1 = AGGRESSIVE (default), 2 = PASSIVE, 3 = LEAPS).


• -s #: Set frequency step in kHz (default is 100000).


• -p #: Polling frequency in milliseconds (default is 1000).


• -u #: Upper CPU usage limit percentage [0..100, default is 80].


• -l #: Lower CPU usage limit percentage [0..100, default is 20].

A Word About Limitations

Caution!

The -U and -L options may not be exact due to how cpufreq drivers round up to the next available step. For example, if my iBook supports two frequencies—400MHz and 900MHz—and I set an upper limit of -U at 800000 (or 800MHz), PowerNowd would still toggle between those two speeds because writing to scaling_setspeed sets it to the next available state—900MHz in this case.

A Peek at What's New!

This release marks the final version since it's feature complete and has been thoroughly tested. The 'ondemand' kernel governor seems like a solid choice moving forward! Also included are minor cleanups.