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Re: Cancel Sleep

On Dec 31, 2007, at 11:08 AM, Jordan K. Hubbard wrote:
Thanks much for the citation. Clearly, I'd never read that before, and it represents an interesting collision between "conventional wisdom" and "the documentation." I'd always heard, both inside and outside of Apple, that running a mac laptop of almost any ilk with the lid closed was a dicey proposition given the variances of heat dissipation.

It is. More modern laptops (including Macs) have fans for active cooling, in contrast to earlier ones which vented via convection through the keyboard, but you still need airflow. If you close the lid and throw your laptop in a case or sleeve without it going to sleep, you can very easily overheat it, and possibly damage it permanently. After one incident of the latch popping loose in the case (which made a MacBook Pro heat up so much it was quite literally too hot to pick up), I routinely use pmset to disable lidwake completely.

My interpretation of "you can operate a laptop with the lid closed only if you have an external display and keyboard attached" is that it's a safety interlock--if you have an external display and keyboard attached, it's very likely that the machine is not closed up in a case, and thus has sufficient airflow.

Now, it could be argued that the test should be based on actual temperature, not on the presence of external devices. This is how desktop machines generally work (example: liquid-cooled CPUs when the pumps fail). However, given the somewhat convoluted thermal environment of a modern laptop, testing for external connections seems like a reasonable compromise.

Going back to Andrew's original question, though... Andrew, can you give us a better idea of the use case you're trying to implement? There may be other ways to solve your actual problem.

--Amanda

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References: 
 >Cancel Sleep (From: Andrew James <email@hidden>)
 >Re: Cancel Sleep (From: Terry Lambert <email@hidden>)
 >Re: Cancel Sleep (From: David Alger <email@hidden>)
 >Re: Cancel Sleep (From: "Jordan K. Hubbard" <email@hidden>)
 >Re: Cancel Sleep (From: Brian Mastenbrook <email@hidden>)
 >Re: Cancel Sleep (From: "Jordan K. Hubbard" <email@hidden>)



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