nearly-working support for cpufreq on 2004 iBook G4 with 7447Acpu

Benjamin Herrenschmidt benh at
Tue Jun 1 12:53:50 EST 2004

On Tue, 2004-06-01 at 12:05, John Steele Scott wrote:
> > Oh, and when switching to high speed, think about tweaking the
> > voltage too. I don't know if it's high or low when setting the
> > GPIO bit, you may want to check out OF code, it certainly have
> > methods for that. Or you can read the voltage value back from
> > the adt themometer chip I think, as it does voltage control.
> I will double-check this tonight (am at uni now), but I thought that the
> core voltage for this chip does not change with frequency . . . :(

It probably does since there is a GPIO for controlling it on
KeyLargo. It's not the chip itself that changes it, you use the GPIO
to change it before/after the freq. switch. That's wher the real saving
comes from, more than the freq change itself in fact.


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