Re: [ACPI-sppt] Who controls cpu fan (Asus M2N) ?

On Thu, Jul 03, 2003 at 06:06:23PM +0200, Rainer M. wrote:
> Hello, 
> 
> I'm using acpi with my Asus M2400N and kernel 2.40 and acpi patch 20021122 
> successfully and a customized dsdt table. 
> 
> In my Linux system, I'm not running some kind of daemon which controls the cpu 
> fan with respect to the current cpu temperature. 
> 
> There's a bios option, which is called "Intel Speed Stepping", where I can 
> choos from the following options:
> - Maximum Performance
> - Battery optimized
> - automatic
> - disabled
> 
> The effect of this is, that the bios determines the cpu frequency and cpu fan 
> speed *at boot time* for the entire session:
> 
> If "battery optimized" is chosen, cpu freq T5 (50%) and fan is off. 
> If "max. performance" is chosen, cpu freq is 100% and fan toggles between full 
> power and off according to current heat situation. 
> (when "automatic" is chosen, it just depends on whether or not the ac adapter 
> is plugged in at boot time). 
> 
> Obviously, I'm rather interested in the "battery optimized" variant, for I can 
> not stand the noise of the cpu fan running at full power. Once Linux is 
> booted, I use some speed stepping program, which adjusts cpu clock according 
> to the current cpu load, so that I'm not confined to the 50% cpu clock the 
> bios preselected at boot time. 
> 
> But:
> For some strange reason, the cpu fan would _never_ switch on during such a 
> session, not even when I'm compiling something! 
> 
> When starting in the maximum performance mode, the fan gets switched on an off 
> very often, and during compilation, it runs permanently. 
> 
> So, I'm seriously concerned as to whether battery mode is really healthy for 
> my processor. 
> 
> And therefore my question is: Wo controls the cpu fan? Is it usually an acpi 
> software, which controls it, or is it usually done be the bios?
> 
> And is there some security built in; I mean, provided that an acpi software is 
> supposed to control the fan, what if my machine hangs with full cpu usage and 
> this peace of software is no longer able to take care of that my processor 
> keeps it's temperature? 
> 
> And incidentally, what's the role of the dsdt table in this process? Does this 
> table determine the bios' fan policy? So maybe I could just fix this table in 
> order that the bios is able to control the fan properly. 
> 
> Any one who knows some answers to my questions? Or anyone who experienced the 
> same?
> 

Hard to answer.  Is your fan controlled via ACPI ?  If not, then
there is good chance that, especially if your laptop is new, that
the FAN is controlled by the EC.
On old hardware, it is more likely to be controlled via the host smbus.
I cant, without looking your dsdt, tell more.

Cheers,

-- 
Ducrot Bruno

--  Which is worse:  ignorance or apathy?
--  Don't know.  Don't care.


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