[CentOS] Checking fan state

John R Pierce pierce at hogranch.com
Mon Jan 5 23:41:08 UTC 2009

Joseph L. Casale wrote:
>> I read something in a forum, that said the CPU temperature can go to
>> 100 C., in a few seconds, but I now wonder if that is true or not.
> Yeah, turn on a machine w/o a heatsink :) In a couple of seconds it will
> get so hot that you can't touch it and the internal safety threshold on the
> proc will shut it down. I suspect the mobo might have a bios that can control
> the fan speed and the hysteresis or whatever technique it uses to control
> reaction time. My Asus has this IIRC...

the newest Intel chipsets actually have all this built into the ICH9R or 
whatever, managed by microcode running in the northbridge as a 
management coprocessor.   I forget what Intel 4-letter-acronym this is 
under.    However, this does NOT play well with the legacy LM style way 
of doing things from the host, and I suspect many of the third party 
boards continue to use LM or similar sensor chips on the i2c bus, old 
school, rather than relying on this chipset built-in fan control 
stuff.    I have an Intel branded G33 board (running Windows XP) and 
none of the usual fan control programs like SpeedFan have a clue how to 
talk to this stuff.   I'll guess without any specific knowlege that 
Linux lm_sensors will have similar problems.

Intel calls this coprocessor on the Northbridge the Management Engine 
(ME) and Host Embedded Controller Interface (HECI), and system wide its 
branded Intel "Quiet System Technology" (QST), which includes the MCH w/ 
ME, the ME Firmware, and the associated BIOS support.   Apparently once 
configured by the BIOS, this runs without host OS intervention, 
including monitoring the CPU, northbridge and southbridge thermal 
sensors, cpu and chassis fan tach sensors and PWM for the respective fans.

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