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Re: powerbook fan behaviour, therm_adt7467

On 26 Oct 2004 at 15h10, Georg C. Kaindl wrote:


> > As long as you make sure there's some code to switch the fans to
> > full speed at some threshold you should be safe. The module needs
> > some more tweaking anyway - it's written for iBook where there's a
> > CPU and GPU fan but the PowerBook seems to have just two exhaust
> > fans, and the sensors don't sit on the CPU and GPU, exactly (the
> > 'GPU' sensor really measures the power supply temp).

Mmh, iBooks only have one CPU fan. Powerbooks 15" and 17" have both. I
thought the second one was on GPU (read it somewhere). That's not such a
big deal anyway :)

> > For me, the 'GPU' limit needs to be reduced or both fans need to be
> > synced to identical speed to keep the machine from crashing too
> > often. Depending on your sensor and fan locations, you might benefit
> > from similar tweaks (list the fan node in the OF device tree, mine's
> > at uni-north/i2c/fan).
> anyways, if you have 2 exhaust fans, it would make sense to set the
> limit to min(cpu_limit, gpu_limit) for both of them... however, if I'm

GPU limit is higher because it's higher by default, and this is
necessary because it won't cool down enough: I currently have:
CPU: 47
GPU: 65

If the GPU limit was at 50 too, it would stay higher for too long and
the hardware would shut the laptop down. 

> > Making the fan start out slower and gradually increasing the speed
> > would be just a minor add-on :-)
> message received, I'll look into that... it would probably be nice to
> have another module parameter like "fan_step" and "limit_override", so
> that when the temperature reaches "limit", the fan speed is set to
> fan_speed and then gets increased by fan_step every one or two degrees
> until limit_override is reached which would in turn set the fan to
> full speed.

I'd like to keep it simple stupid. If you want a stepping, you'll end up
with a lot of code to handle hysteresis - which is, don't slow down the
fan as soon as the temp is going under one limit (or the other way) or
your fan will change speed every two seconds. Which is very
annoying to hear...
Currently the fan starts at lim, stops at lim-2, goes
full speed at lim+8, goes normal speed at lim+6. That's already four
cases :)

> does anybody know how OS X handles the fan speed i.e. at which
> temperatures does it start the fan(s),

Same as us (+/- 4 degrees).


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