[RC5] RC5 on laptops & CPU temperature

Elektron elektron_rc5 at yahoo.ca
Sat Nov 6 09:54:46 EST 2004

> I've found out that it makes a significant difference for the cooling 
> fan speed (and sound tone), whether the laptop rests on its small legs 
> and draws the intake air from a small clearing between the bottom and 
> any solid surface. If there is more room for the intake air to reach 
> the fan inlet, it will decrease the intake air resistance and require 
> less rpm for the fan to achieve the same cooling airflow. I don't 
> think it makes that much difference with the surface temperature 
> whether there is a few mm of air space or nothing at all between the 
> laptop bottom and the surface it's sitting on. Even if the surface is 
> aluminium, it probably won't form a good enough thermal interface with 
> the laptop bottom to transfer much heat via conduction unless there is 
> some other mating material in between. Keeping the lid open should 
> allow some heat escape from heating the air in contact with the top 
> and perhaps some circulating inside leaking from small gaps in the 
> keyboard etc.

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 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).

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).

- Purr

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