Re: Booting the Debian installation CD on Powerbook G4 12"
On Sun, Feb 16, 2003 at 06:05:19PM +0100, Benjamin Herrenschmidt wrote:
> On Sun, 2003-02-16 at 17:12, Benjamin Herrenschmidt wrote:
>
> > > My kernel has support for cpu frequency scaling via /proc/cpufreq --
> > > and now when it boots it claims to be at 53 MHz. You can get this up
> > > to the proper 867 MHz by doing
> >
> > Are you sure of the 53Mhz bit ? Isn't it 533 ?
>
> Actually, looking at a device-tree dump, it seems the min frequency
> reported by Open Firmware is indeed 53Mhz. I suspect it's a bug in
> OF on this machine (either that or Apple added a way to scale to
> more than 2 frequencies).
It would be very surprising, since it would mean that the bus runs
very slow too. Which is:
a) likely to be impossible for reasons like the frequency range
of various PLL in the system and in the processor.
b) will not save energy actually. Even if the voltage is dropped
at low frequencies, there is a limit below which you can't drop
it.
c) at such a low frequency, you have to keep the bus drivers
activated for much longer on every transation, which is likely
to actually increase power consumptiom on very light CPU loads.
Gabriel.
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