sysctl debug.cpufreq.highest

[Kevin Oberman]

> From: Bruce Cran <bruce at cran.org.uk>
> Date: Wed, 6 Oct 2010 07:18:38 +0100
> Sender: owner-freebsd-current at freebsd.org
> 
> On Wednesday 06 October 2010 03:02:36 Alexander Kojevnikov wrote:
> 
> > This variable allows to underclock the CPU, which is useful when
> > building quiet or low-power systems.
> 
> You can use the new -m and -M switches to powerd to control the minimum and 
> maximum frequencies instead.

Ack! Did this really make it into the code? This is NOT the answer. the
answer is to get rid of the useless CPU throttling and TCC which is the
real cause of this. 

Neither of these methods was designed as a power management mechanism.
They were designed to keep the processor from over-heating. They both
can do what they were designed for quite well, but they can provide only
very limited power savings and can actually result in higher power
consumption in some cases. (I reported on my research into this several
years ago, but the definitive work was done by mav@ and can be read
on the FreeBSD wiki at http://wiki.freebsd.org/TuningPowerConsumption

If we would just get rid of this (or at least turn it off by default),
this whole problems requiring -m would go away. (I can see real use for
-M, though.)
-- 
R. Kevin Oberman, Network Engineer
Energy Sciences Network (ESnet)
Ernest O. Lawrence Berkeley National Laboratory (Berkeley Lab)
E-mail: oberman at es.net			Phone: +1 510 486-8634
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