Re: Speedstep on Celeron SU2300

[Thomas Renninger <trenn@suse.de>]

On Thursday 02 September 2010 01:17:14 Tiago Marques wrote:
> Hi Thomas. Thanks for the message.
> 
> On Wed, Sep 1, 2010 at 11:40 PM, Thomas Renninger <trenn@suse.de> wrote:
> > On Sunday 29 August 2010 06:54:44 Tiago Marques wrote:
> >> Hi,
> >> I'm having a problem with this processor not having frequency steps
> >> and apparently only voltage steps. I find it very strange but that's
> >> what Intel's documentation suggests. I can't load acpi-cpufreq because
> >> it doesn't find any device and battery life in linux is suffering
> >> around 20% less due to this.
> > Where do you have the 20% info from, I doubt you verified it?
> 
> Yes. Since it seems no one can't return Windows licenses for refunds
> anymore, I have went ahead and booted windows on it, without any
> driver installed and just configured it to have frequency scaling
> working, which in this case is only voltage scaling.
> I measured almost 6 hours of battery life and the processor & chipset
> frequently had the fan stop when idling.
> 
> In linux, in the same conditions, I got less than 4 hours and the fan
> never stops. I configured a PCI-express power saving feature on the
> kernel and it seems to have dropped noise a bit. Battery life is still
> not great and the fan still never stops. I'm trying to find something
> with which I can measure the actual power going through the AC adapter
> but for now battery life tests is pretty much all I can do.
There is current battery power drain somehwere in
/proc/acpi/battery/*/*
It normally updates not that often, but may be better and accurate enough if you
take several values, than waiting for the battery got drained.

> The 20% figure is obviously optimistic since I'm accounting a positive
> effect from the PCI-Express power saving feature to not quote 33%
> less.
Yep, this could be the graphics card as well.
What kind of graphics card has it and which driver are you using?

> >> I have confirmed that the CPU supports
> >> Speedstep, just this very strange variation.
> > You are not the only one:
> > https://bugzilla.kernel.org/show_bug.cgi?id=16072
> > [HP Pavilion dm1-1110ev] Cpufreq doesn't work at all ( Intel Celeron U2300 )
> > or the last comments (or search for U2300) here:
> > http://software.intel.com/en-us/articles/enhanced-intel-speedstepr-technology-and-demand-based-switching-on-linux/
> >
> >> Can I somehow help with this to get it fixed? Who are the current maintainers?
> > Not exporting cpu frequencies seem to be intended for this cpu for whatever reasons.
> 
> It doesn't have more than one. I checked in windows and I also can't
> change frequency, despite reports from a person on the contrary:
> 
> http://scottiestech.info/2010/02/05/how-to-increase-your-laptops-battery-life-a-lot-with-crystalcpuid/
> 
> I have confirmed that the GM45 chipset doesn't support frequency
> scaling of the FSB on Intel's datasheet, so the speed he reports of
> 98MHz is a bug. I found similar frequencies upon use. Since I
> performed my tests with LCD brightness in full, that would account for
> the one hour difference on the best result, while the less than four
> hours he also reports may be due to speedstep not working before he
> messed with configurations.
> 
> I tried the same program and the CPU is locked at 6x, although the
> voltage isn't, it's somewhere from 0.925 to 1.075v if I recall
> correctly.
> 
> > If you have efficient C-states, frequency states are not that important.
> 
> I know. But what about voltage? Intel's datasheet clearly states this
> processor supports two voltage states, I guess for the purpose of
> relaxing clock binning requirements for these CPUs. I'm thinking it
> does scale when in windows.
> The Pentium SU4100 has similar problems but he allows one p-state,
> from 1300MHz to 1200MHz.
> I can't seem to find the lowest multiplier available on these
> platforms, CrystalCPUID lists mine as 6x, hence 1200MHz. I thought
> Core 2's could idle at something like 800MHz and I find it strange
> that this one can't also.
Interesting. Possibly you have luck finding a document from Intel about
this CPU describing this a bit. I'd be interested in the outcome, but don't
have to time to dig for it.

     Thomas