Power Saving Linux G5 iBook/Powerbook g4( 7447a 750fx )

[DearthnVader]

Seems we can control bus slewing on the G5 and DFS on the G4( 7447a ) and this would likely also work for the G3 750fx.

First let's load some modules if they aren't already loaded.

sudo modprobe cpufreq_ondemand cpufreq_conservative cpufreq_powersave

Now let's look at the modes we have available:

cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_governors

On my sysetems Quad G5 and iBook G4, with the modules we loaded we have:

conservative ondemand userspace powersave performance schedutil

Now on the G5's and G4's we only really have two frequencies to chose from, and we can just set powersave or proformance, but if we want the system to switch between those two modes depending on demand of the CPU then we need to set conservative/ondemand.

Ondemand doesn't seem to work on my G5 Quad, it always seems to stay at 2500000Mhz, so I use conservative and that seems to switch between 2500000Mhz and 1250000Mhz.

su
echo conservative > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
exit

Now we can check the frequency

sudo cat /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_cur_freq

On the Ibook G4 I seem to have good luck with ondemand:

su
echo ondemand > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
exit

Works the same way for powersave performance, if you are just trying to save battery life or don't want the fans to spin up so fast on the G5, and you don't really need max cpu speed:

su
echo powersave > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
exit

There is also a way to just set the speed in Mhz, but with the G5/G4/G3 there is only 2 speeds to chose from and powersave/performance covers these two speeds.

Should work on iBooks with the 750fx and G4 systems upgraded to 7448's( the 7448 should have three modes full/half/quarter, but I don't have a 7448 to test.