Enhanced SpeedStep driver available

Kevin Oberman oberman at es.net
Tue Aug 17 14:39:04 PDT 2004

> Date: Tue, 17 Aug 2004 10:37:52 +0300
> From: Paulius Bulotas <paulius at devnull.lt>
> Sender: owner-freebsd-current at freebsd.org
> Hello,
> On 04 08 16, Colin Percival wrote:
> >   I've also put together a very simple control daemon which
> > reads kern.cp_time every second and adjusts the cpu frequency
> > based on the fraction of cpu time which is idle.  This increases
> > my laptop's battery life by around 40%.
> works with my T40 with Pentium M 1300MHz. Only I doubt it would increase
> life on battery, since the lowest speed is 600MHz. And if I run on
> battery all the time, it's always 600MHz. So, now it only raises speed
> (which still is good, since it makes cpu intensive jobs run faster), but
> how this could prolong battery life? In normal conditions on battery I
> can work ~2 hours (and in Windows ~4, but I use them rarely). So now
> probably less? Or this has to do something with voltage?

Assuming that your T40 works like my T30, it runs at the clock speed
selected at boot time. So, if you boot on battery, you run at a slow
speed (1.2 GHz on my T30). If you plug into AC, you stay there.

Conversely, it you boot on AC and switch to battery, your speed stays at
the max (1.8 GHz on my T30). So, it I had Enhanced SpeedStep on my T30
(I don't), I could boot on battery and speed up the CPU when I get to my
power supply and, more importantly, I can pull the plug while something
is running and reduce CPU speed to keep my battery alive for a while.
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

More information about the freebsd-current mailing list