Systems running hot?

Kevin Oberman oberman at
Sun Dec 20 06:33:32 UTC 2009

> Date: Sat, 19 Dec 2009 19:20:19 -0800
> From: Doug Barton <dougb at>
> Sender: owner-freebsd-current at
> Glen Barber wrote:
> > On Sat, Dec 19, 2009 at 9:27 PM, Doug Barton <dougb at> wrote:
> >> Paul G Webster wrote:
> >>> tried running powerd on it?
> >> I was not running powerd, but I just enabled it with:
> >> performance_cx_lowest="HIGH"
> >> performance_cpu_freq="HIGH"
> >> economy_cx_lowest="HIGH"
> >> economy_cpu_freq="HIGH"
> >>
> >> If I'm reading the rc.conf man page correctly, that will give me the
> >> benefit of good performance while at the same time dropping the cpu
> >> frequency and power usage when idle?
> >>
> >> Any other suggestions are welcome.
> >>
> > 
> > You can also set settings dependent on the power source:
> > 
> >    powerd_flags="-a max -b adaptive"
> I set it to "-a adaptive -b adaptive" (I'm on AC power most of the
> time) and the good news is that the temp dropped by about 10 degrees C
> and the fan went down to the low speed for the first time today.
> My concern about using this feature is that the last time I used it I
> ended up with problems with my (build into the motherboard) video
> card. I was never sure at the time whether or not the problem with the
> video card was a result of powerd, or of the heat problems I was
> having at the time (back in 8-current when everyone agreed that there
> was a heat problem). I'd like to think that powerd would not fry a
> graphics card, and I don't think that it's even likely, but the system
> is out of warranty now and I can't afford to foul it up.
> The other negative to running powerd is that it causes my display to
> flash occasionally (which of course feeds my "powerd is destroying my
> graphics card" paranoia). It's not life threatening, but it is annoying.
> Thanks to everyone for their suggestions, we'll see how this goes ...
> Doug

powerd has undergone major revision lately (I think in 7.2 and 8.0) to
greatly enhance responsiveness. I have moved to running adaptive at all
times and no longer notice slowness when I kick off some CPU intensive

Beyond that, read Alexander Motin's power management article at when it's available. (It
seems that the wiki is down at the moment,) Note the comments on
throttling/TCC and deep sleep states. He and I both found TCC and
throttling not worthwhile and possibly causing very unpleasant
side-effects. C (sleep) states are a really big win, but cause problems
on a few systems. 

mav did a great job on this, duplicating my work back in V5 days and
taking it a lot farther than I did. Anyone who wants to save power and
heat really should read it.

I also found the original article at
I'm not sure it's identical to the wiki entry, but it is very close and
is currently available.
R. Kevin Oberman, Network Engineer
Energy Sciences Network (ESnet)
Ernest O. Lawrence Berkeley National Laboratory (Berkeley Lab)
E-mail: oberman at			Phone: +1 510 486-8634
Key fingerprint:059B 2DDF 031C 9BA3 14A4  EADA 927D EBB3 987B 3751

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