iMac G5: experimental thermal & cpufreq support

Markus Demleitner msdemlei at
Fri Sep 30 20:22:59 EST 2005

On Thu, Sep 29, 2005 at 05:51:50PM +1000, linuxppc64-dev-request at wrote:
> I now have some experimental thermal control and cpufreq support for
> iMac G5. I have not _yet_ implemented support for the SMU based single
> CPU desktops (PowerMac9,1), those will have to wait a little bit more
> (not too much hopefully, but I need potential testers to contact me as I
> lack hardware access). At this point, it should work on PowerMac8,1
> (iMacG5 rev A) and PowerMac8,2 (iMacG5 rev B).
First data on cpufreq support: Power consumption on idle for a 1600
MHz iMac G5 is down to about 50 Watts with the powersave governor
from about 74 Watts without voltage control (ok, display off in both
instances).  Thanks, Ben.  U Heidelberg owes you for saving it quite
a bit of electricity.

For some reason the conservative and ondemand governors don't work as
I'd expect them to from my x86 experience.  I hope I'll be able to
look into the matter next week.

Thermal control has various little problems for me (like
windfarm_lm75_sensor: Unknown parameter `windfarm_pid') that I don't
have time to figure out right now, either (another todo for next
week).  At least my little hack
( still works with the new

Nitpick: I had to enable SMP in .config to get the cpufreq support
built (otherwise boot_cpuid, get_hard_smp_processor_id and friends
are undefined).  That doesn't feel quite right.

Thanks all,


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