Re: Speedstep on Celeron SU2300 - 20% more battery lifetime on Windows

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On Tue, Sep 7, 2010 at 5:43 PM, Thomas Renninger <trenn@xxxxxxx> wrote:
> On Tuesday 07 September 2010 17:22:46 Matthew Garrett wrote:
>> On Mon, Sep 06, 2010 at 10:47:58PM +0100, Tiago Marques wrote:
>>
>> > Yes, but shouldn't it detect P-States with different voltages, as in
>> > windows? (even as stupid as this sounds) I sure loved to get it always
>> > stuck at the lower clock, given that I usually perform maintenance on
>> > PCs I highly doubt the fan would get dust clogged to the point of
>> > taking the CPU to temperatures that would cause problems.
>> > This looks like it doesn't support Speedstep even though Intel says it
>> > does but the fact is that Windows can work with two voltages, which
>> > always improves power.
>>
>> If there's only one frequency then there's no reason to have multiple
>> voltages - the voltage will already be at the minimum possible for the
>> core to be stable at that frequency. Entering C4 will typically result
>> in the voltage dropping as parts of the core are disabled.
>>
>> Does your chip have the "est" flag in /proc/cpuinfo? If not, it doesn't
>> support speedstep.
> That is somewhat strange. These CPUs show est support in cpuinfo, also
> compare with (not only about HP, but also other OEMs):
> [Bug 16072] [HP Pavilion dm1-1110ev] Cpufreq doesn't work at all ( Intel Celeron U2300 )
> https://bugzilla.kernel.org/show_bug.cgi?id=16072
>
> But Tiago digged out an Intel spec which says that the SU processors do only
> run at one freq:
> http://www.intel.com/design/mobile/datashts/321111.pdf
> page 30, note 10, at the top of the page.
>
> I could imagine cpuid should not export est capabilities for these and
> cpufreq drivers should not complain that an est capable CPU is found for
> which no frequencies get exported, but probably only Intel can tell for
> sure.

I'd love input on this, because with the lower voltage being there I
could probably get away with using it even in load usage since I tend
to keep vents clean and temperatures here aren't high. coretemp is
showing me around 60ÂC in load. To me, having a lower voltage when the
CPU has to come out of C4 into C0 is an advantage, one which I hope to
measure. When having the CPU run at C0 in light loads(<50%) would also
be useful to have the lower voltage there, kicking it up when the two
cores are +80% to keep stability in check with the temperature rise(if
needed...). Or am I completely wrong and when having 50% load the CPU
also does a lot of C4 idling?

The only reason I took the plunge with a Celeron processor, besides
being the only one available in the DM1 around here, was that it
supported EIST. I would not get one laptop without it, so let's say I
was a bit perplexed when I tried to get it to run and failed.

Best regards,
Tiago


>
> Â Â Thomas
>
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