[ltp] Re: tpfand configuration for an X200s

[Henrique de Moraes Holschuh]

On Sun, 07 Dec 2008, Elias Oltmanns wrote:
> Please keep in mind that there is not a trivial correlation between
> temperature readings and fan speed. In particular, hysteresis enters
> into it which can be easily observed on my X40. When I keep working for
> a long time with active wlan but otherwise restricting myself to
> lightweight tasks like reading emails, browsing the web, etc. and the
> fan starts spinning eventually (this only happens in a reasonably warm
> environment), then it won't stop for a very long time. On the other
> hand, when I compile the kernel which challenges the CPU as well as the
> HD, then temperature readings rise quickly and the fan gets into gear
> accordingly. Quite shortly after compilation has completed, the fan
> stops spinning at temperature readings that are well above the
> thresholds that would have caused the fan to stop in the first scenario.

Hysteresis is all and good, but what you describe is an outright bug in the
firmware...

But a X40 will change the target RPM speed of the fan levels depending on
battery state, etc.  You can see it in the ACPI DSDT.  Other ThinkPads
(including newer X models) can't do it (from ACPI, at least).

-- 
  "One disk to rule them all, One disk to find them. One disk to bring
  them all and in the darkness grind them. In the Land of Redmond
  where the shadows lie." -- The Silicon Valley Tarot
  Henrique Holschuh