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XNorth

macrumors 6502
Original poster
Feb 23, 2018
300
464
United States
I use clamshell mode in a vertical stand to save desk space. Does clamshell mode generate more heat and reduce performance under a heavy load? Wondering if anyone’s noticed a difference between clamshell and open lid.

My MPB 16” is connected a LG 5K monitor for FCPX video editing, transcoding, rending, color grading, mostly 4K and some RAW video.
 
Yes, significantly. While compiling a large library my 2.4GHz i9 CPU temps reached ~100C with the clamshell closed and cooled off to ~80C within 30 seconds of opening the lid.
 
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Yes, but not just the 16", any reasonably powerful laptop in clamshell mode operating under load will generate more heat and potentially cause a reduction in performance.

With it venting at the side and back put it in the stand with the back edge at the top (heat rises) and it will help a bit but there is not much you can do without additional airflow other than use a stand that allows the device to remain open.

I have been using a mini USB fan close by and directed at mine just to take the edge of things and works quite well, dropping the temp by 10C.
 
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My personal experience is that it generated a lot of heat, more then I was willing to put up with. I stopped using clamshell mod due to the heat. YMMV
 
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I was told somewhere else here, that a MBP actually runs cooler with the lid closed, because it has to power less internals.
 
I think it's only under load that this is a problem, but yeah.... I even have a PC gaming laptop over here that I started leaving the lid open on when using an external display because in "clamshell" mode on it, the video card automatically drops back to a lower frame-rate to reduce the heat output.
 
I can’t understand why there is no easy way to shut off the internal screen without closing it. That would be the best option I think
 
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They suggest 3 possible ways to accomplish this.... but really, two are pretty inconvenient. (I'm not going to change a PRAM setting from the command line every time I want to do it, and the magnet trick is just cheesy.)


I can’t understand why there is no easy way to shut off the internal screen without closing it. That would be the best option I think
 
Yes, significantly. While compiling a large library my 2.4GHz i9 CPU temps reached ~100C with the clamshell closed and cooled off to ~80C within 30 seconds of opening the lid.

That’s a big enough difference that performance would be negatively impacted by throttling.

My personal experience is that it generated a lot of heat, more then I was willing to put up with. I stopped using clamshell mod due to the heat. YMMV

You’d think Apple should mention/warn this about clamshell mode. I see potential for lawsuit.
 
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They suggest 3 possible ways to accomplish this.... but really, two are pretty inconvenient. (I'm not going to change a PRAM setting from the command line every time I want to do it, and the magnet trick is just cheesy.)
I used to use a magnet sometimes, but I'm too scared that I forget about the magnet, close the lid and damage the screen.
So it's clamshell only for me
 
My 15" 2019 definitely does not feel as hot to the touch in clamshell compared to an opened lid. This thing gets so hot, that I don't want to touch it at all.
But, that might be because it has some issues. So that does not have to be the norm. After talking twice to the Apple support I'll get it (hopefully) repaired.
 
I'm not sure having a computer run hotter in clamshell mode, is worthy of a lawsuit - I just said in my personal experience it was hotter ¯\_(ツ)_/¯

Not saying there’s any merit in such a lawsuit, but it’s an excuse. If there is evidence that higher temps in clamshell mode shorten the life of a laptop and Apple doesn’t disclose it — it’s surprising there has been no lawsuit, given how much people like to sue Apple with all kinds of worthless claims.
 
You’d think Apple should mention/warn this about clamshell mode. I see potential for lawsuit.

The fact that a computer runs hotter in one configuration is not an indication of a defect. When the computer is closed, it's got less exposed surface area to use for cooling, so it should be no surprise it runs hotter.
 
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