FreeBSD & SpeedStep

[Kevin Oberman]

> Date: Fri, 11 Jun 2004 11:07:49 +0200
> From: Bruno Ducrot <ducrot at poupinou.org>
> Sender: owner-freebsd-mobile at freebsd.org
> 
> On Fri, Jun 11, 2004 at 11:01:31AM +0200, Frank Altpeter wrote:
> > 
> > Hello!
> > 
> > Bruno Ducrot wrote on 2004-06-11 03:25:07 +0200:
> > > On Thu, Jun 10, 2004 at 11:47:01PM +0200, Eduardo Mínguez Pérez wrote:
> > > > Hi!
> > > > This is my first mail to the list and I want to sorry for my english
> > > > (I'm spanish ;D)
> > > > My question is... Is speedstep supported by FreeBSD? My notebook is a p4
> > > > mobile (1,7 Ghz)
> > > 
> > > Not yet.
> > This answer only applies AFAIK to 4.x FreeBSD versions. 5.2-CURRENT
> > does indeed support speedstep technology.
> 
> No.
> 
> > 
> > # dmesg | grep step
> > acpi_cpu: throttling enabled, 8 steps (100% to 12.5%), currently 100.0%
> 
> The processor will be throttled, so frequency will change somehow.  But
> the voltage (which is the key to speedstep technology) will be the same.

Actually, it's not really even that. The clock runs at the same speed,
but the duty cycle is reduced to accomplish the "throttling". That allows
it to work with little hardware requirements, but means that, if you are
testing CPU speed, it will not change.

SpeedStep is actually far more sophisticated. It is not in either V4 or
V5 at this time, but should be coming to V5 fairly soon. Depends on the
time the small number of developers who understand the newbus and ACPI
stuff has available.

>From the March-April status report:
   Much of the ACPI project is waiting for architectural changes to be
   completed. For instance, the cpufreq driver requires newbus
   attachments for CPUs. Support code for this should be committed at the
   time of publication. 
-- 
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