Whirliwig’s Weblog

The following is ripped directly from here: http://web.mit.edu/jjl/www/mm10/

It worked as described.

Transmeta LongRun

The Crusoe can adjust its own clock speed to save power when processor load gets low. There are 2 modes for this: performance and economy. Using the economy mode will save battery life, but it takes longer to speed the processor up when under load. I will soon be testing just how much this helps, though it really depends on how you use it.

In the kernel config, enable /dev/cpu/*/cpuid and /dev/cpu/*/msr support. If /dev/cpu does not exist, you will need to do:

mkdir -m 0755 -p /dev/cpu/0

and then create the msr and cpuid devices. Do that with the following:

mknod /dev/cpu/0/msr -m 0444 c 202 0

mknod /dev/cpu/0/cpuid -m 0600 c 203 0

You will need to install the longrun package (in Gentoo, just emerge longrun). Type longrun -p to show the status. To switch to economy mode, type longrun -f economy. For performance mode, use longrun -f performance. You can also set performance windows (i.e. if you want the Crusoe to never run at 100% speed so you can save battery power, type longrun -s 0 50 to set the window to 0 (low) to 50 (high)). By default the window is 0-100. Here is a table showing what the performance levels are (you can get this info from longrun -l):

# % MHz Volts usage

0 300 0.800 0.114

19 433 0.875 0.196

33 533 0.950 0.285

52 667 1.050 0.435

71 800 1.150 0.626

85 900 1.250 0.832

100 1000 1.300 1.000