General question regarding CPU fan
Hi,
I've been playing around with Linux and my iBook G4 lately to better
adapt the first to the latter and now I have a question regarding the
driver for the iBook CPU fan (the therm_adt746x module).
Without the module loaded the iBook is as quiet as it is when running
Mac OS X, even under heavier load, i.e. when compiling a kernel. With
the module loaded, every now and then the fan starts to get really
noisy. I think it is switched to full speed or so. That never happens
with OS X, even when running programs that are heavily using the CPU,
like the SETI@home client for example. I still haven't got around to
set up lmsensors to monitor CPU temperature under Linux (can anyone
here give me a hint at how to do this with the 2.6 kernel?) but
regarding my experiences with Mac OS X the temperature goes up to about
75 degree Celsius and then stays quite constant, even when running
SETI@home for some hours, without any fan noise. So I don't think
compiling a kernel produces more load for the machine which would
justify running the fan at full speed. I've been running the iBook under
Linux for some time now, without the therm_adt746x module, and I've
compiled a new kernel quite often, but it never showed any signs of
overheating. So my first question is: Is there any kind of hardware fan
control built in to the iBook? Does one really need to use therm_adt746x
or can one safely run the iBook without it?
The second questing is: When using the module it provides some files in
/sys/devices/temperatures to get information on things like temperature,
fan speed and so on. When the iBook is all quiet, cpu_fan_speed reports
82, and when the fan gets nosiy, it reports some higher values. Does
"82" actually mean "the fan runs at 82 rpm"? Or is it just some synonym
for "the fan isn't active"?
I hope someone here has a deep enough insight into this hardware/driver
stuff to answer my questions.
Bye, Michael
--
Indifference will be the downfall of mankind, but who cares?
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