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

Pavel Machek
2004-01-15T12:18:33Z

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.

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

Pavel

--
When do you have a heart between your knees?
[Johanka's followup: and *two* hearts?]