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This is how you enable external display with open Macbook Pro in Lion!

J

JacksTLOS

macrumors member
Original poster
Aug 31, 2011
54
57
So you want to use an external display, full external display resolution and all, with your Macbook Pro lid open... enter the following into the Terminal:

sudo nvram boot-args="iog=0x0"

This will make the Macbook Pro behave exactly like it would in Snowkitty.

To return to Lion behavior simply reset PRAM or enter this:

sudo nvram -d boot-args

:cool:

Let me clarify! To run the Macbook Pro, with it's display off and lid open, run the terminal command.
 
Last edited:
you can also do this by turning the brightness all the way down too, or am i missing something?


i do this when i have my laptop hooked up to my HDTV watching 1080p bluray .mkv's, because i have my macbook on my display center and don't want any extra light/distractions.
 
JacksTLOS said:
So you want to use an external display, full external display resolution and all, with your Macbook Pro lid open... enter the following into the Terminal:

sudo nvram boot-args="iog=0x0"

This will make the Macbook Pro behave exactly like it would in Snowkitty.
Click to expand...
Great find! I've been looking for this. For all those who posted above with smart comments, there are plenty of reasons to do this.

Turning screen brightness does not have the same effect. Your video RAM is still spread between two displays, hot corners (if set up) do not work properly, and windows (or the mouse cursor, highly annoying!) can still get dragged to the 'off' display. The display is still on if you turn the brightness down, you just don't see it.

Two main reasons I've found for keeping lid open while using laptop in clamshell mode:

1. Heat. There absolutely is a difference in heat; either measured by the computer's sensors or, more easily, with your hand. Let your Macbook do something processor intensive for a while with its lid closed, then open it and feel the heat both on the keyboard and screen. That heat escapes easily with the lid open. Less heat equals longer life for any electronic component.

2. Wireless transmission rates. I have measured network file transfer speeds with both the lid open and closed. I've seen anywhere between 10-20% increase in transfer speed with the lid open as opposed to closed. That can make a significant difference in various situations.
 
Interesting and great find. Also, Heb pretty much hit the head on the nail. It may be a niche type of setting, but it can be an extremely useful one
 
At last! A normal solution! That way I won't look stupid when I'm using a magnet and the remote control every time I need to enable only my external monitor. Too bad Apple didn't bother to find it (or announce it, who knows?) so the users who actually want to use their laptops as desktops, don't really have to waste energy, or decrease the valuable hours of working time of their built-in displays. I can't wait to go home and try it.
 
EEXOOO said:
What do I have to do after running the command in Terminal?
Click to expand...

You may have to restart after the terminal command. Then it should work just like snow leopard! start computer and attach external, once you can see screen on external close macbook pro. Wake macbook using external keyboard, mouse, trackpad. Once everything is running on external you can open the lid to the macbook and the computer won't automatically detect built in display.
 
JacksTLOS said:
You may have to restart after the terminal command. Then it should work just like snow leopard! start computer and attach external, once you can see screen on external close macbook pro. Wake macbook using external keyboard, mouse, trackpad. Once everything is running on external you can open the lid to the macbook and the computer won't automatically detect built in display.
Click to expand...

Thanks for the great find and explanation. I got it to work after a restart. Finally I do not have to use the magnet mod. Thank you so much :)
 
lauph said:
But why should the display be disabled?
Click to expand...

Because when you're using a large display like the 27" ACD then the extra space may not be required. I have some of the highest resolution available wrt to the mbp (27" ACD @ 2560x1440 and 17" Hi-Res MBP @ 1920 x 1200) but I usually drive only with the 27" on.

Having it on also consumes video memory (although with 1GB vRAM that may not be an issue depending on what you're doing). Simply turning down the brightness and calling it good doesn't help either, as your mouse may end up over there or you may have issues with full screen apps.
 
Heb1228 said:
.........

1. Heat. There absolutely is a difference in heat; either measured by the computer's sensors or, more easily, with your hand. Let your Macbook do something processor intensive for a while with its lid closed, then open it and feel the heat both on the keyboard and screen. That heat escapes easily with the lid open. Less heat equals longer life for any electronic component.

..................
Click to expand...
This.


The fan "intake" is the keyboard area. Hence the lack of grills in the base of the MBP (and Air)
 
danpass said:
The fan "intake" is the keyboard area. Hence the lack of grills in the base of the MBP (and Air)
Click to expand...

Heh. Not in the MBP.

Notice the construction of the fan. One end acts as an intake as the other is the exhaust in the same unit.

Also notice the all black covering that separates the keyboard from the fans and logic board. It's a nonporous sheet.

(img courtesy of ifixit)
 

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Jrv said:
Alternatively, keep pressing the brightness button...


And now someone probably feels stupid...
Click to expand...

DWBurke811 said:
you can also do this by turning the brightness all the way down too, or am i missing something?


i do this when i have my laptop hooked up to my HDTV watching 1080p bluray .mkv's, because i have my macbook on my display center and don't want any extra light/distractions.
Click to expand...

Turning the brightness down does not turn off the screen. It only dims it. Even at the lowest setting, the screen is still on.
 
JamesGorman said:
Turning the brightness down does not turn off the screen. It only dims it. Even at the lowest setting, the screen is still on.
Click to expand...

Yup.

Honestly, I thought this forum had technical people ... But from the stuff I read on here sometimes, it seems I was wrong.
 
While I've known of this for quite some time, I find it stupid that you have to run a terminal command to do something Windows 7 does in a keyboard combo press.
 
Wow this fixed one of my biggest gripes about Lion. Kudos to the OP. I hope apple brings this functionality back in future updates.
 
Hyper-X said:
While I've known of this for quite some time, I find it stupid that you have to run a terminal command to do something Windows 7 does in a keyboard combo press.
Click to expand...

You only have to run the command once... it's not like it's a setting you have to keep changing or running the command every time!
 
danpass said:
This.


The fan "intake" is the keyboard area. Hence the lack of grills in the base of the MBP (and Air)
Click to expand...

The reason I use it too. MPB gets hot and this allows me to use external monitor in full res.]

Thanks for the info!
 
I used my new MBP in clamshell mode for the first time lastnight and it worked like a dream. My average temp was 51c. Shes a fine machine. A fine machine
 
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