iMac G5 cpufreq

Markus Demleitner msdemlei at
Wed Apr 13 00:28:20 EST 2005


I just noticed that I cannot select cpufreq capabilities for an iMac
G5 kernel -- I'm not enough of a kconfig buff to see what exactly
keeps the power management/cpufreq from appearing, but I guess the
reason is there is no driver for the G5's frequency scaling
capabilities (then again, I have no idea if it requires chipset
support just yet, either).

So: Could anyone give me a hint what would be required to do CPU
frequency scaling on G5s?  And is there any known documentation 
or source code out there that might be helpful in doing whatever is

Background: Even when stretching the intervention thresholds in my
exprimental fan control, I notice that OS/X makes do with *much* less
fan activity, and I strongly suspect they simply reduce the CPU
frequency (though I can't be sure: they do draw 10 Watts more power
in my standard cat /dev/zero > /dev/null load, even while keeping the
fans off).  Now, I'd rather reduce the CPU speed than increase the
fan speed, but...



(PS: Don't bother to cc: me, I'm on the list)

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