is it really better speedstep-ich vs. p4-clockmod cpufreq driver?

is it really better speedstep-ich vs. p4-clockmod cpufreq driver?

[Riccardo Vestrini]

it seems that speedstep-ich and acpi cpufreq driver have only two usable
clock frequencies, while p4-clockmod has eight
my cpu is: Intel Mobile Intel(R) Pentium(R) 4   CPU 3.06GHz stepping 09



last 2.6 kernel I tried (2.6.7) has introduced a warning while loading
p4-clockmod module:

p4-clockmod: P4/Xeon(TM) CPU On-Demand Clock Modulation available
p4-clockmod: Warning: Pentium 4-M detected. The speedstep-ich or acpi
cpufreq modules offer voltage scaling in addition of frequency scaling.
You should use either one instead of p4-clockmod, if possible.

so I immediatly switched to speedstep-ich discovering that:
$ cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_frequencies
3066590 1599960

while with p4-clockmod I have:
$ cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_frequencies
383323 766647 1149971 1533295 1916618 2299942 2683266 3066590

using acpi driver gives a message:
cpufreq: CPU0 - ACPI performance management activated.
cpufreq:  P0: 3059 MHz, 24000 mW, 100 uS
cpufreq: *P1: 1596 MHz, 12000 mW, 100 uS
but:
$ cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_frequencies
3059000 1596000


i do not know what driver is supposed to be better and why speedstep-ich 
driver has only two frequencies

thank you

-- 

                                Riccardo Vestrini
                               <riccardov@sssup.it>

Re: is it really better speedstep-ich vs. p4-clockmod cpufreq driver?

[Rutger Nijlunsing]

On Fri, Jul 23, 2004 at 08:54:39PM +0200, Riccardo Vestrini wrote:
> it seems that speedstep-ich and acpi cpufreq driver have only two usable
> clock frequencies, while p4-clockmod has eight
> my cpu is: Intel Mobile Intel(R) Pentium(R) 4   CPU 3.06GHz stepping 09
> 
[snip]
> 
> i do not know what driver is supposed to be better and why speedstep-ich 
> driver has only two frequencies

p4-clockmod is not really a cpufreq driver: it does not change the
frequency. The only function is to have 'idle-cycles' to cool down the
processor during intensive CPU programs: this is what the processor
does when it gets too hot.

The speedstep driver _does_ change the frequency (and/or voltage) and
gives other advantages like less power consumption.

So use speedstep.

-- 
Rutger Nijlunsing ---------------------------- rutger ed tux tmfweb nl
never attribute to a conspiracy which can be explained by incompetence
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