Re: Booting the Debian installation CD on Powerbook G4 12"
On Wed, 2003-02-19 at 03:26, Segher Boessenkool wrote:
> Benjamin Herrenschmidt wrote:
> > On Mon, 2003-02-17 at 02:07, paubert wrote:
> >>Well, the timebase and decremeter are part of the PPC architecture.
> > I'm not sure things like 4xx implement them "as-is"...
> It is part of the user-level 32-bit PEM -- they better
> implement it :)
Hrm... right, tb is indeed there, DEC isn't (40x uses PIT)
> >>BTW for the "53 MHz PB", what are the following properties of cpus/PowerPC,G4:
> It is 53_300_000 Hz, and it is most probably a typo
> in the OF. All other such values are rounded to
> exact millions.
It is a typo, it works fine if I "fixup" the value.
> If you're going to reimplement the delays using the
> time base, why not use the KeyLargo timer instead?
> It runs at the same frequency (18.432MHz) on all
> machines, so that'll save a multiply ;) Too bad for
> the non-Macs, but else you'll have to special-case
> the 601 (and maybe others) anyway.
I don't want to rely on external HW, IOs are slow, KL doesn't exist
on all macs, and other PPCs would benefit from TB based delays as well
KL timer would be useful for better calibration of TB during boot
on pmacs though (Darwin recent versions use it for that as well).