powerd to use sysctl to import temps to drop freq to avoid heat crash

[Kevin Oberman]

On Tue, Jan 3, 2012 at 7:45 PM, Warner Losh <imp at bsdimp.com> wrote:

>
> On Jan 3, 2012, at 6:38 PM, Dmitry Kolosov wrote:
>
> >
> >>      hw.acpi.thermal.tz0.temperature: 67.0C
> >>      hw.acpi.thermal.tz0.active: -1
> >>      hw.acpi.thermal.tz0.passive_cooling: 1
> >>      hw.acpi.thermal.tz0.thermal_flags: 0
> >>      hw.acpi.thermal.tz0._PSV: 90.0C
> >>      hw.acpi.thermal.tz0._HOT: 95.0C
> >>      hw.acpi.thermal.tz0._CRT: 100.0C
> >>      hw.acpi.thermal.tz0._ACx: -1 -1 -1 -1 -1 -1 -1 -1 -1 -1
> >>      hw.acpi.thermal.tz0._TC1: 2
> >>      hw.acpi.thermal.tz0._TC2: 3
> >>      hw.acpi.thermal.tz0._TSP: 40
> >
> > Use
> > hw.acpi.thermal.user_override=1
> > in sysctl.conf to allow override of thermal settings. Now you can set
> custom
> > _PSV, _HOT and _CRIT. Worked well for me on my previous HP Pavilion dv6
> series
> > laptop.
> > More complex resolution of overheating problem - consider to sell HP
> asap and
> > get any other laptop. HP totaly failed on cooling on almost all models,
> they
> > are all hothothot.
>
> I fought for two years the overheading of my HP laptop.  Some of the
> following might help, or they might not:
>
> (1) blow the dust out of the dang thing.  HP's clog up with dust making
> their fans about useless.
> (2) make sure the fans are spinning at full speed.
> (3) replace any broken fans
> (4) give up and get a different computer...  that's what I did in the end
> (although not until after the power board went out on the goofy thing).
>
> Warner
>

While I am not about to defend HP and would never consider buying any HP
system, laptop or desktop, the dust issue is common to all systems, laptop
and desktop, but shows up more in laptops as they are often used in places
where dust is a bigger issue and have very compact cooling systems which
are far more sensitive to anything that degrades performance.

It's not so much clogging. That takes a huge amount of dust and, more
likely, lint. Dust is a great insulator and a thin coating of dust on the
fins of a laptop heatsink will greatly diminish heat transfer.

I have learned over the past decade and a half  that it is really important
to blow out the dust on heatsinks annually. I monitor my CPU temps with
gkrellm and over the months after cleaning the heatsink idle temperature
will slowly climb from fairly cool (52-55 on my old T43) to over 60. The
loaded temperature will climb dramatically. A buildworld with clean
heatsinks will run at 78 or 79 while a year later I will see temperatures
at or near 90. While the numbers vary, I have seen the same sort of
behavior on all of my laptops, about five of them.
-- 
R. Kevin Oberman, Network Engineer
E-mail: kob6558 at gmail.com