Re: [ACPI] Re: [PATCH 2.6] update passive cooling algorithm

[Ducrot Bruno <ducrot@poupinou.org>]

On Thu, Jan 15, 2004 at 01:18:33PM +0100, Pavel Machek wrote:
> Hi!
> 
> > > > > [Len, could you test and verify this patch, and push it to Linus, please?]
> > > > > 
> > > > > The current algorithm used by Linux ACPI for passive thermal management has
> > > > > two shortcomings:
> > > > 
> > > > ...
> > > > 
> > > > > +/* If a passive cooling situation is detected, primarily CPUfreq is used, as it
> > > > > + * offers (in most cases) voltage scaling in addition to frequency scaling, and
> > > > > + * thus a cubic (instead of linear) reduction of energy. Also, we allow for
> > > > > + * _any_ cpufreq driver and not only the acpi-cpufreq driver.
> > > > > + */
> > > > 
> > > > Just a stupid question:
> > > > 
> > > > What is best if processor heat issues (apart turning on the fan)?
> > > > 
> > > > Reducing voltage of the processor, but still allowing it to run execution
> > > > at 100% (which is the case if the processor is heating), or reduce
> > > > amount of time allowed for the processor to execute?
> > > 
> > > voltage scaling. It offers a much better (quadratic) saving than clock
> > > modulation (linear saving). Doing both [and you need to do it, as the CPU
> > > won't run with fewer volts at the same frequency] gives you cubic savings.
> > 
> > Yes I know.  But does it offer more 'cooling'?
> 
> Of course.
> 
> If you eat less power, you create less heat. CPU is basically fancy
> "turn-electricity-into-heat" device.
> 

I don't like certitudes (I was wondering if better heat dissipation in
case of throttling even if more heat generation, but that not the case).

> [Have you seen that "first use of PentiumPro in house appliances"
> picture?]

No, but I do have seen some that have burnt in a production server,
some years ago...

-- 
Ducrot Bruno

--  Which is worse:  ignorance or apathy?
--  Don't know.  Don't care.