Re: cpufreq on TiBook II (was: Powerbook G4 getting very hot. Solution?)
On 18/07/03 17:20, Teemu Ikonen wrote:
> On 18/07/03 14:41, Kiko wrote:
> > Well, first thing you must know: does your cpu support frequency
> > scaling? Don't know if your TiBook does, I would bet it does, but really
> > have no idea.
> Well I don't know either, but after checking the latest 2.4.21-benh
> kernel source I found that this particular model of TiBook (Powerbook3,3) is
> not supported in the cpufreq code. For some reason most of the other models
After a bit of playing around with the powermac cpufreq code in the kernel,
I found that I can at least make my 550 MHz G4 Powerbook to switch between
the nominal frequency of 550 MHz and something which is around 500 MHz. I
have no means I know of to verify the exact frequency, but testing with the
bogomips program and other speedtests shows around 10% decrease in
performance.
Attached is a patch against the 2.4.21-benh kernel, which turns on the
cpufreq support in the 550 MHz TiBook II. If someone with the 667 MHz model
wants to test this, please modify the code accoordingly, or ask me how to do
it. I'd be interested in hearing about the results.
I would also be interested in the programming information concerning the PMU
found in powerbooks. Does anyone know any good resources on the net?
Teemu
The patch (against linux/arch/ppc/platforms/pmac_cpufreq.c):
*** pmac_cpufreq.c.orig Fri Jul 18 17:26:08 2003
--- pmac_cpufreq.c Sun Jul 20 17:03:22 2003
***************
*** 291,296 ****
--- 291,306 ----
has_freq_ctl = 1;
cpufreq_uses_pmu = 1;
}
+ /* Else check for TiPb 550 */
+ else if (machine_is_compatible("PowerBook3,3")) {
+ /* We only know about 550Mhz model */
+ if (cur_freq < 500000 || cur_freq > 600000)
+ goto out;
+ hi_freq = cur_freq;
+ low_freq = 500000;
+ has_freq_ctl = 1;
+ cpufreq_uses_pmu = 1;
+ }
/* Else check for TiPb 500 */
else if (machine_is_compatible("PowerBook3,2")) {
/* We only know about 500Mhz model */
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