Laptop Thermal Problem

Rod Haper rhaper at houston.rr.com
Sat Dec 24 04:28:53 UTC 2005


At work I recently got a new Dell Latitude D810 which is going to 
replace my trusty 3 year old Inspiron 8100.  I've run FC2 and FC4 on my 
8100 and have never had any problems.  I installed FC4 on the new D810 
and everything works just fine ... except that I getting thermal shutdowns.

The D810 is of recent manufacture - the BIOS is A04 (09/30/2005).  The 
processor is a 1.86Ghz Pentium M with Centrino SpeedStep.  SpeedStep 
works okay using the userspace or ondemand governors.  Part of the 
problem may be due to sensors-detect not being able to find any sensors 
or i2cdetect to find any i2c buses.  No one seems to know what sensor 
chips Dell is using in this laptop.  I wrote a script to log the CPU 
temperature from /proc/acpi/thermal_zone/THM/temperature (I have no idea 
what sensor it is reading) and then exercised the CPU with a tiny C 
program doing integer addition and multiplication in a tight loop (top 
shows 100% user/0% idle) to force the CPU temperature to rise.  Shutdown 
occurs at 40C.  There's no fan sensor data but the cooling fan seems to 
running full speed.

Now here's the strange part.  If I boot up Knoppix 3.9 Live CD, there is 
no problem with thermal shutdown even when exercising the CPU.  The 
temperature rises steadily to around 53C or 54C and then decreases back 
to around 33C and holds steady.

If I boot the Dell hardware diagnostics and run the non-interactive CPU 
tests in an infinite loop there is never a thermal problem.  It ran 
overnight with no problem.

And finally, if I boot the M$ XP PRO that I kept around on a small 
partition and exercise the CPU there is no problem with thermal shutdown.

So I'm fairly confident that there is not a problem with the hardware.

But what is different about FC4?  Why does my D810 work with Knoppix and 
M$ XP but fail with FC4?  What am I missing?  If there is anyone that 
has a D810 with the A04 BIOS and not having this thermal shutdown 
problem with FC4, I'd sure like to hear about it and what if anything 
you did to avoid this problem.




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