Enhanced SpeedStep driver available

[Kevin Oberman]

> Date: Sun, 05 Sep 2004 19:54:17 +0300
> From: Maxim Sobolev <sobomax at portaone.com>
> Sender: owner-freebsd-mobile at freebsd.org
> 
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> Please see attached a patch which adds support to TCC speed control 
> available in every intel p4 processor. This patch requires up-to-date 
> current system to work properly, since I've recently addes ESS-like 
> sysctl that can be used to obtain list of speed steps supported by TCC 
> circuit.
> 
> It would be nice to have it integrated into the estctrl.

I'd love to see a good description of TCC, SpeedStep, and ESS. 

I have learned that TCC and ACPI CPU throttling are additive. (TCC set
to 25% and throttling of 25% results in 12.5% performance), but I am
unsure of the advantages of one over the other. I did read an article on
TCC that said that speed an be manually set or t can be run in
"automatic" mode where the processor will slow down a the CPU heat up.
Is there BIOS/hardware support for this automatic capability or is it
purely software? I see no way to get it with FreeBSD.

Do any of these tie in with ACPI in some way? Will the eagerly
anticipated cpufreq work? Is there some reason for so may ways to do
about (but not quite) the same thing? SS, CPU throttling, ESS, TCC all
are pretty similar on the surface, but I suspect far less so under the
covers. 

I'd just like to find a good document that discusses any (or better yet,
all) of the options so I can decide the best way to configure my
laptop. 
-- 
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