Become a MacRumors Supporter for $25/year with no ads, private forums, and more!

eoblaed

macrumors 68030
Original poster
Apr 21, 2010
2,780
2,642
I'm using a new 16" MBP to drive a pair of external monitors (one LG 4K Ultrafine, and one LG 4K 27UL600-W).

I normally run with the lid closed, just using those two larger monitors so I have room for a full sized kb, etc.

My concern is that sometimes the fans kick up pretty hard on the MBP and I'm concerned that with the lid closed, that prevents some of the heat from escaping that normally would (eg. through the keyboard, etc).

I'm wondering if there's a way to run with the lid open, but just powering those two external monitors. In the absence of that, I'll run with lid open and just arrange the monitors so the laptops screen is 'out of the way'.
 

BigMcGuire

macrumors G3
Jan 10, 2012
8,403
10,372
the Alpha Quadrant
I also feel the same way. I turn brightness all the way down on my MBP so it shuts off the backlight and then in Display I have my laptop screen on the bottom right corner of the 4k display I use so I don't accidentally send the mouse to it. The Primary display is the 4k display so I never have a problem with stuff going to the laptop screen.

Not exactly what you wanted, but it's what I do. :p
 

itakemycoronawithalime

macrumors member
Mar 6, 2020
56
30
I'm using a new 16" MBP to drive a pair of external monitors (one LG 4K Ultrafine, and one LG 4K 27UL600-W).

I normally run with the lid closed, just using those two larger monitors so I have room for a full sized kb, etc.

My concern is that sometimes the fans kick up pretty hard on the MBP and I'm concerned that with the lid closed, that prevents some of the heat from escaping that normally would (eg. through the keyboard, etc).

I'm wondering if there's a way to run with the lid open, but just powering those two external monitors. In the absence of that, I'll run with lid open and just arrange the monitors so the laptops screen is 'out of the way'.

The 16" MBP pulls less wattage with the lid closed. The dGPU pulls ~20W when pushing my Ultrafine (2 of them) 23.7" displays with lid open.

Lid closed just pushing the two displays wattage drops and bounces around 5-9W. Heat reflects the numbers as well, runs cooler closed.
 
  • Like
Reactions: silvetti

caupljx

macrumors newbie
Mar 15, 2020
26
11
The 16" MBP pulls less wattage with the lid closed. The dGPU pulls ~20W when pushing my Ultrafine (2 of them) 23.7" displays with lid open.

Lid closed just pushing the two displays wattage drops and bounces around 5-9W. Heat reflects the numbers as well, runs cooler closed.

How do you connect your MBP with the monitors? Mine still pulls ~18W when just pushing one Dell 2K monitor.
 

eoblaed

macrumors 68030
Original poster
Apr 21, 2010
2,780
2,642
How do you connect your MBP with the monitors? Mine still pulls ~18W when just pushing one Dell 2K monitor.
With OP mentioning Ultrafine 23.7" they are likely the LG 4K displays sold in Apple stores - if so, they're probably daisy chained via TB3

I have the 4K Ultrafine plugged in directly via USB-C. The LG 4K 27UL600-W only has HDMI and Display Port outputs. I tried the HDMI at first, but no matter what adapter/cable I used, could only get 30hz when running full resolution. So, I got a Display Port to USB-C cable, and have that also plugged directly into the MBP, and am getting 4K@60Hz that way. No daisy chaining.
 

profcutter

macrumors 65816
Mar 28, 2019
1,087
738
I’m curious, folks are saying it runs cooler closed, but is it possible that’s just because it’s not driving an additional display? What if you could fool the computer into thinking it was closed, but with the clamshell open, would it run cooler?
 

peite

macrumors newbie
Jan 3, 2011
8
1
I’m curious, folks are saying it runs cooler closed, but is it possible that’s just because it’s not driving an additional display? What if you could fool the computer into thinking it was closed, but with the clamshell open, would it run cooler?
Yes it's only running cooler because of the internal screen being off.
What I do on my 2012 Retina MBP 13" is I have placed a small fridge/whiteboard magnet (I would not recommend using strong magnets since it could probably damage the internal electrics) directly above the left USB-slot.
By doing this you fool the MBP to beliee it is closed since there is an magnet on opposite side on the screen (you can try by holding something metallic to the middle left rim of the screen).

My big question to you all is HOW ABOUT M1 MBP??

Do I still need to use this sketchy magnet-trick on an expensive new Mac or have they finally added ability to choose which screen I want to feed the signal to which you are able to do in Windows?!
 

profcutter

macrumors 65816
Mar 28, 2019
1,087
738
Yeah, that’s what I’ve done for years on my older MBPs. I was just wondering if the mechanism is the same on the newer machines.
 
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.