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

Discussion in 'MacBook Pro' started by JacksTLOS, Aug 31, 2011.

  1. JacksTLOS, Aug 31, 2011
    Last edited: Aug 31, 2011

    JacksTLOS macrumors member

    Aug 31, 2011
    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


    Let me clarify! To run the Macbook Pro, with it's display off and lid open, run the terminal command.
  2. Steve's Barber macrumors 6502a

    Jul 5, 2011
    What am I missing?

    I just plug in my external display and it works. No need for terminal hacks.
  3. Darby67 macrumors 6502

    Jul 5, 2011
    the corner of Fire and Brimstone
    No difference in behavior between SL and Lion with either of my external displays. Not sure what settings you have that have made it goofy, but happy it works for you again.
  4. kappaknight macrumors 68000


    Mar 5, 2009
    Why would anyone do this? If you're looking for screen real estate, why not use both screens? Heck, park an iPad next to it and make it three screens.
  5. DWBurke811 macrumors 6502a

    Jun 10, 2011
    Boca Raton, FL
    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.
  6. Jrv macrumors regular

    Aug 17, 2011
    Long Beach, California
    Alternatively, keep pressing the brightness button...

    And now someone probably feels stupid...
  7. Heb1228 macrumors 68020


    Feb 3, 2004
    Virginia Beach, VA
    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.
  8. WonkyPanda macrumors regular


    Mar 29, 2010
    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
  9. lauph macrumors regular

    Jun 29, 2007
    30 mins from Cupertino
    I see some reasoning for having the lid open... But why should the display be disabled?
  10. eC1990ho macrumors member

    Mar 1, 2011
    Does this help your fps on the external monitor?
  11. EEXOOO macrumors regular

    Aug 1, 2009
    What do I have to do after running the command in Terminal?
  12. Kiriga macrumors newbie


    Sep 22, 2009
    Somewhere in time...
    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.
  13. JacksTLOS thread starter macrumors member

    Aug 31, 2011
    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.
  14. EEXOOO macrumors regular

    Aug 1, 2009
    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 :)
  15. Eddyisgreat macrumors 601

    Oct 24, 2007
    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.
  16. danpass macrumors 68020


    Jun 27, 2009
    Miami, FL

    The fan "intake" is the keyboard area. Hence the lack of grills in the base of the MBP (and Air)
  17. Eddyisgreat macrumors 601

    Oct 24, 2007
    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)

    Attached Files:

  18. JamesGorman macrumors 65816


    Dec 31, 2008
    Turning the brightness down does not turn off the screen. It only dims it. Even at the lowest setting, the screen is still on.
  19. EEXOOO macrumors regular

    Aug 1, 2009
    I'm curious, how did you came about this command?
  20. Adamantoise macrumors 6502a

    Aug 1, 2011

    Honestly, I thought this forum had technical people ... But from the stuff I read on here sometimes, it seems I was wrong.
  21. Hyper-X macrumors 6502a

    Jul 1, 2011
    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.
  22. XandeR803 macrumors member

    Jul 25, 2008
    Wow this fixed one of my biggest gripes about Lion. Kudos to the OP. I hope apple brings this functionality back in future updates.
  23. JacksTLOS thread starter macrumors member

    Aug 31, 2011
    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!
  24. UTHorn macrumors member

    Aug 3, 2010
    The reason I use it too. MPB gets hot and this allows me to use external monitor in full res.]

    Thanks for the info!
  25. Alexjones macrumors 6502

    May 28, 2010
    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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