Netbook Thermal Issues

Recently there has been increasing attention paid to thermal issues. The power used by computers not only impacts the electricity bill (and battery life for a portable device) but is a cooling problem. The waste heat from desktop systems and servers costs energy (and therefore money) to remove by the air-conditioning system and the heat produced by small devices can impact where they may be used.

It seems that a temperature of 40C can cause burns if applied to the human body for any period of time. As it doesn’t immediately hurt this can happen without people noticing. A friend recently reported getting a large blister on his arm after drinking a moderate amount of alcohol and falling asleep next to his EeePC.

I have noticed that my EeePC 701 has an unpleasant pattern of heat dissipation. It appears to use only one small vent in the side to vent most of the heat (with some vents in the base for air intake) and the base is all plastic. Apparently such a machine draws 14W from the wall when in active use compared to my measurements of 20W for a Thinkpad T41p. The Thinkpad however has a significantly greater size, this means bigger vents (and therefore lower temperatures of the vented air). Also the fan inside the Thinkpad makes much less noise so I guess it’s larger.

If I am working in the lounge and leave my Thinkpad on the couch it doesn’t seem to have any thermal issues. But if I leave my EeePC sitting in a normal manner the vents on the base are partially blocked and it becomes unpleasantly hot. If I leave my EeePC upside-down with the lid closed (so that the vents in the base are exposed to the air) then the screen gets very hot, I am not sure whether this is heat from the CPU going through the keyboard to the screen and then being prevented from going further by the insulating cushion or whether heat is generated in the screen (although it is supposed to be powered down when the lid is closed).

One suggestion I have received is to place a laptop on a metal baking tray. The flat tray preserves the airflow underneath it and the metal conducts heat reasonably well. Baking trays seem to be made of aluminium or thin steel, they don’t conduct heat well – but a lot better than a cushion.

It seems to me that one factor which will limit the development of NetBook class machines is the ratio of heat dissipation to either area or volume (I’m not sure which is more important). For use similar to mine providing the same compute power as an EeePC 701 with less heat dissipation would be ideal – and technically should not be difficult to achieve. Unfortunately I think that people will want to run Windows on NetBook class machines so we will see the development of machines with faster CPUs and GPUs which have worse ratios of heat to heat dissipation potential which will lead to more heat induced shutdowns and low temperature burns.

It’s a pity that no-one makes a netbook with the CPU power of an iPaQ. A 400MHz ARM CPU is all I need for my portable computing and my iPaQs don’t have cooling vents.

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