Hi Guys

Kevin Oberman oberman at es.net
Wed May 13 20:08:30 UTC 2009

> Date: Wed, 13 May 2009 15:33:42 -0300
> From: =?ISO-8859-1?Q?Sylvio_C=E9sar_Teixeira_Amorim?= <scjamorim at bsd.com.br>
> Sender: owner-freebsd-acpi at freebsd.org
> I have one laptop Dell Latitude E4300 with FreeBSD-8-Current, The
> temperature of the processor is very high when I'm compiling the kernel, I
> get to stay with 88 Celsius, how do I force a download this temperature?

Probably the first place to start is to clean the heat sink on your
laptop. Simply opening the unit and blowing it out with compressed air
can drop CPU temperature by over 10 degrees Celsius. This is probably
something that should be done at least annually and more often if the
laptop is run in dusty locations, such as sitting on a bed or table
covered with a table cloth.

It is also possible that the heatsink is not properly attached to the
CPU. Several people have reported that cleaning and re-applying heatsink
grease greatly improved the temperature.

Next, take a look at the values of _PSV and _CRT. (sysctl hw.acpi). If
PSV is higher than 88, your system is still within normal operating
temperatures. For example, Pentium-M chips are speced to run at a steady
temperature of 100C. _PSV on my laptop is 94.5C and _CRT is 99.0C. This
means that the system does not start doing anything beyond normal fan
cooling until the CPU reaches 94.5C and will reach 99C before starting
to shutdown. (This is different from the emergency crowbar shutdown
which is for thermal spikes of about 130-150C which might occur when a
heatsink becomes dislodged.)

When _PSV is reached, the system should simply slow down until the
temperature drops. There is hysteresis to keep it from continually
cycling. I don't recall numbers, though.

If you want to lower the temperature "manually", you can kill powerd
(/etc/rc.d/powerd stop) and set the CPU frequency lower. (sysctl
dev.cpu.?.freq) where '?' is the CPU number. The available frequencies
may be found in sysctl dev.cpu.0.freq_levels. If you are doing the
manually, be sure to adjust all CPUs to the same frequency.

Finally, placing the system on a surface that leaves an air gap under
the system will help, too. Running it on a soft surface inhibits
convection cooling and most soft surfaces are pretty goods thermal
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
Key fingerprint:059B 2DDF 031C 9BA3 14A4  EADA 927D EBB3 987B 3751

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