[RC5] RC5 on laptops & CPU temperature

SideWinder sidewinder at kolumbus.fi
Sat Nov 6 17:54:17 EST 2004

At 16:54 6.11.2004, you wrote:
>The iBook's air intake is along the left side (near the front), so I don't 
>think this would make that much of a difference.

That's one possible configuration. However, in all laptops that I've used 
(none of them Apple though), the primary intake has been in the bottom, 
with a secondary intake in the side (to allow minimal airflow even when the 
bottom is completely covered by a soft surface).

>That said, people do buy stands (or piles of books) to levitate their 
>iBooks. I'm not sure how much this helps (probably quite a lot, since I'm 
>quite sure the cooling fan is either on or off, and when it's off, the 
>heat has to find other ways to get out).

Again, this is probably something specific to iBook (and a few very cheap 
PC laptop models I've encountered). Usually there is stepless adjustment of 
the fan voltage (between 3-5 V) from a CPU thermistor imput or at least a 
few different speeds. If you wanna real quiet operation even when under 
stress, take off the top cover (or keyboard) and place a large passive 
heatsink directly on top of the thermal module, with some silicon paste in 
between (I had to do this once when my fan broke down and I had to get some 
stuff out of the machine before receiving the replacement fan).

>There could also be things to lower your clock speed (I think the iBook 
>does this when it goes into display sleep, because one morning the fan 
>went on due to dnetc, which means it was running all night, without waking 
>me up with the horribly loud fan).

AFAIK the usual CPU energy saving technologies (Cool'n'Quiet, PowerNow, 
SpeedStep, etc.) work by reducing the core clock/multiplier/voltage when 
they detect low demand. They should not touch the CPU if it's constantly at 
100% utilization.

In any case, my opinion about the thermal failure risk is that I'd much 
rather have any machine, laptop or desktop, crash and burn when it's just 
running Dnetc on its own than in the middle of me working on something 
important with it. If it can't handle Dnetc, it needs to be 
repaired/replaced anyhow.


 >------->- SideWinder -<-------<

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...Computer Science: solving today's problems tomorrow.
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