Thinkpad Thermals

[Kevin Oberman]

> From: Jesse Guardiani <jesse at wingnet.net>
> Date: Fri, 04 Mar 2005 13:01:21 -0500
> Sender: owner-freebsd-mobile at freebsd.org
> 
> Howdy!
> 
> My IBM Thinkpad A30p's ATI video chip got cooked last year,
> leaving me with an unreadable screen full of artifacts. I
> finally bought a replacement mobo a few days ago and installed
> it this evening. It's now running artifact free! Yay!
> 
> Anyway, I'm no longer running FreeBSD on this laptop. I'm
> currently running Gentoo Linux. But it would be trivial
> to switch back if needed.
> 
> I'm using gkrellm under linux to monitor my CPU temp, and
> I'm noticing that it runs quite hot. The fan doesn't kick
> in until the CPU hits 80C! That's a little too close for
> comfort, IMO.
> 
> I think I remember seeing other posts from Thinkpad users
> mentioning high temps under ACPI. Has anyone found a way
> to cool these things down?

Jesse,

Is it running at or near 80C when idle, when in typical use, or when
building something BIG (CPU running at >95% for minutes).

I believe that the A30p is a P4-M CPU. It will turn itself off (hard,
like a power cut-off) before the CPU dies, but that is NOT a good
thing. That does not happen until the CPU reaches a frightening 135C.

If you are running 5-Stable or 6-Current you should load cpufreq and
acpi_perf. These will give you a large number of CPU "frequencies"
visible in dev.cpu.0 and settable in dev.cpu.0.freq. This provides
fine-grained control.

Yo can also look at hw.acpi.0.thermal for _PSV and _CRT. _PSV is the
temperature at which the CPU should start to slow down to moderate the
temperature. _CRT is the point at which alarms are sounded and the OS
should start a clean shutdown. If there is no cooling problem _PSV
should keep the temperature from ever reaching _CRT. You will note that
these temperatures are WAY under 135C, but the 135C cutoff is intended
for catastrophic failures (like a broken/improperly installed heat sink)
and assumes that the temperature rose very quickly. It is not intended
that the CPU should run at that sort of temperature normally. 

FreeBSD is still working on support for all of this, but it's getting
much closer. The addition of powerd to Current is a big step, but it is
probably not quite ready for prime time and is disabled by default. Nate
just committed it to current a few days ago and I just installed it
yesterday, so I have no experience with it.

Bottom line is that as long as the temperature stays below _PSV under
heavy load, you should not be concerned. If it exceeds _PSV for very
long, you might want to reduce dev.cpu.0.freq a bit. If you ever hit
_CRT, dow something quickly. FWIW, my system has _PSV at 86.5C and _CRT
at 94.0C, so 80C is really not that hot, though my thigh does not agree
when my laptop is literally on my lap.

As always, I am not really an expert on all  of this and I can hope that
Nate or someone else will correct any errors in this.
-- 
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