[CentOS] Checking fan state

John R Pierce pierce at hogranch.com
Tue Jan 6 01:49:25 UTC 2009


re: thermal sensors...  I did a bit of googling.  This NC2400 laptop is 
based on the Intel 945GM chipset w/ the ICH7 southbridge.   the 945GM 
does -not- implement that ME (Management Engine) stuff I previously 
described, instead, it has thermal sensors on a smbus, along with some 
interesting heuristic logic that attempts to guess how hot the memory is 
getting based on cycle rate, and tuned by some registers which can be 
loaded either with BIOS presets or from memory DIMM SPD values...  all 
of this is used to trip 4 possible throttle states just for the GMCH 
(northbridge)...    the Northbridge apparently signals the host 
{bios|os}via ACPI IRQ to manage the fans.

I found the stuff about memory throttling fascinating reading... Chapter 
10.7 of http://www.intel.com/Assets/PDF/datasheet/309219.pdf (the 945GM 
(G)MCH chip)



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