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I have the newest model Unibody MacBook Pro and I've been reading mixed opinions on whether or not it's safe to run my MacBook Pro in clamshell mode or not. I'm thinking of getting an Apple Cinema Display but want to know if clamshell mode causes any damage whatsoever.

Also related to this, does all heat get expelled from the vents on the back of the new MacBook Pro?

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up vote 4 down vote accepted

I have a friend who runs a studio and keeps a Macbook Pro closed and I haven't seen a problem with this.

The only vents are at the back.

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However, I can say from my friends one that the heat pretty much evenly spreads out across the chassis.

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Great, thanks for the quick and precise answer! :) – Kevin Yap Dec 27 '09 at 23:01
Let me add my 2c-worth to the above sample-of-one. I also run a 17-incher in clamshell mode and it works fine with Cinema display attached. Guess for the definitive answer, download istat menus and see if there's any significant temperature difference on the various parts of the machine, between operating modes. – Thomas Browne Dec 27 '09 at 23:57
I've run a plastic '13-inch, Early 2009 MacBook' since 2009 almost exclusively in clamshell mode. She's still going strong. – boehj Sep 4 '11 at 4:15

It will probably run hotter, since the graphics card will be working harder to drive a higher resolution. If you're worried, get the excellent SMCFanControl menu app, and set your base fan speed higher than the normal. I do this a lot when working with large indesign files on my 2007 MBP, as the graphics card makes the lappy super hot.

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I have a 2012 15" MBP (Non-Retina) that I use in clamshell mode most of the time. I've been doing some video encoding for a project I'm working on and was worried about head since when I'm encoding all processors are running at 100% and the fans are going full blast. I purchased iStat Menus to monitor the temperature and I found that while encoding with the screen fully open and processors running at 100% I was running at a steady 117ºF… while encoding with the screen closed and processors running at 100% I am running at a steady 122ºF. So, yes, it's running a bit warmer but that could probably be attributed to the fact that the GPU is powering a 27" Thunderbolt Display instead of the built-in 15" display.

My feeling is basically that Apple has built the clamshell-mode functionality into the machine and I don't think they would have done that if it was going to cause problems. I know that there are a lot of people who run their MBP's in clamshell mode (myself included) and I have yet to meet anyone who had encountered a problem doing this.

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I just got the 24 incher and my unibody 13 inch MBP's fan has been running higher than normal since it's been connected both with the lid closed.

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