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Date: Wed, 2 Feb 2005 21:37:58 +0100
To: Nate Lawson <nate@root.org>
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From: Bruno Ducrot <ducrot@poupinou.org>
cc: acpi@freebsd.org
cc: current@freebsd.org
cc: Colin Percival <cperciva@freebsd.org>
Subject: Re: New cpufreq framework and drivers
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On Wed, Feb 02, 2005 at 12:03:47PM -0800, Nate Lawson wrote:
> Colin Percival wrote:
> >Nate Lawson wrote:
> >
> >>Hardware drivers are of two types, absolute
> >>and relative.  SpeedStep, Powernow, etc. are absolute drivers in that 
> >>they set the cpu's base frequency.  ACPI throttling, Longrun, etc. are 
> >>relative drivers that reduce the processor's clock to a fraction of 
> >>its current base (i.e., they have an additive effect.)
> >
> >
> >If my first glance at the patch is correct, this would have my laptop (a 
> >1.4GHz
> >Pentium M) reporting the availability of the frequencies 600MHz, 800MHz, 
> >etc.
> >from enhanced speedstep, along with the frequencies 300MHz, 400MHz, 
> >500MHz, and
> >700MHz obtained via 50% clock throttling.
> 
> That is correct.  The code to support relative drivers was removed 
> before posting to give the basic framework more testing before I commit 
> it shortly.  The relative support will go in soon after that code is 
> committed.
> 

But longrun is relative though and can scale voltage.
(And the point that longrun can control frequency itself is imho irrelevant).

-- 
Bruno Ducrot

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