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12-inch runs cooler with lid closed
Authored by: nickp on Mar 11, '05 10:35:18PM
I was amazed too, but using Marcel Bresink's excellent Temperature Monitor I found that my 12-inch aluminum powerbook (Rev A) actually ran cooler (by about 1.5 deg C, as I recall) with the lid closed than with the lid open and the LCD turned off. Go figure.

I use a Podium Pad that elevates the rear end of the laptop, and things may be different if it is in contact with a surface. Also, I did this testing before downgrading my AppleADM103x.kext to the one from 10.2.8, as described in this hint and the reply by junkiesxl , which may affect the results.

Perhaps more understandably, it runs even cooler upside-down (in which case the lid must be closed, obviously). At some point, I may re-wire things and see how it runs when positioned vertically, like a book ...

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12-inch runs cooler with lid closed
Authored by: Jeremy M. Dolan on Mar 12, '05 10:01:32PM

I recently purchased one of the new (G4, 1.5GHz) 12" Powerbooks to replace my senile (P2, 266MHz) Linux box as my main PC, for work, school, and everything in between. I planned to use it on my desk, with a "real" keyboard, mouse, and monitor, 90% of the time, so I was a bit taken aback when I found out running these things closed was considered unusual around the Apple community.

So just last week I did my own temperature benchmarks. I can second nickp's observations. (And I was quite surprised as well!) This is driving a 19" SVGA monitor at 1280x, so certainly the graphics card is working harder. I don't think LCDs generate much if any heat, so I doubt that's the cause of the cooldown. But then I noticed that with the screen open, airflow from the three major ventilation ports on the back of the laptop's base are somewhat obstructed. Undoubtedly Apple placed them there to keep the front and sides streamlined, but the screen pivots down right in front of them. Crazy.

Anyway, the point here is that the temperatures are fine. Even playing a little bztank, which heats the GPU to 154ºF (86ºC, for my metric friends) and more, it's usually a degree or two cooler with the screen closed. The only potential issue is screen damage from heat transferring up, of which I can report absolutely no problems. Besides, if the article in Apple's knowledge base says you can do it, and I have the three year AppleCare warrantee, what am I worried about? Worst case scenario, I get a shiny new Powerbook after mine melts into a puddle.


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