Re: Cancel Sleep
Re: Cancel Sleep
- Subject: Re: Cancel Sleep
- From: Amanda Walker <email@hidden>
- Date: Mon, 31 Dec 2007 11:28:23 -0500
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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