rMBP using iMac as external display in Target Display Mode - with lid closed?

Discussion in 'MacBook Pro' started by jennyp, Jun 18, 2014.

  1. jennyp macrumors 6502

    Oct 27, 2007
    Right now I have a mid-2011 iMac, and next to it an ageing mid-2009 MacBook Pro.

    I'm looking to buy a new rMBP when they get updated, and I thought when I do, I'd be able to use the iMac as an external display in Target Display Mode.

    I saw a YouTube video showing how to do this, but I can't seem to find out if it's possible to do this with the rMBP lid closed (aka "clamshell mode'). Would that be possible?

  2. whlabus macrumors newbie

    Jun 19, 2014
    I can't see why it wouldn't. OS X should just treat it as it would any other external display, allowing you to extend the desktop, mirror it, or close the notebook lid and use it as the sole display. One thing to note is that I'm fairly certain only the 27" iMac can be used as an external display, the 21.5" cannot.
  3. simonsi macrumors 601


    Jan 3, 2014
    My 2011 iMac 21.5" can be used as a target display using a TB cable. I think there are model year dependencies for both being and able to use a target display iMac.
  4. Mooseiah macrumors member

    Apr 12, 2014
    San Diego, CA
    There may be a workaround for it, but with just factory programs you need to have it plugged into the power adapter for it to not shut itself off when you close the clamshell :) Works perfect as long as it's plugged in though.
  5. jennyp thread starter macrumors 6502

    Oct 27, 2007
    I should have said that the iMac is the 27 inch.

    Thanks for the info. I get the impression I can do it, as long as the rMBP is connected to power. That's great :)
  6. SVTmaniac macrumors 6502

    Jan 30, 2013
    Connected to power, and an external keyboard, mouse and display attached. That's the requirements for clamshell mode. Any of those are taken away and it will just go to sleep when you close the lid.
  7. qtx43 macrumors 6502a

    Aug 4, 2007
    To prevent sleeping, you might try opening a terminal and typing:
    caffeinate -i read
    I think that should work, haven't tried it with an external display. Then to go back to normal, go to the terminal and type some input and return (or control-C).
  8. defboob macrumors member

    Jun 17, 2008
    Yep you definitely can. I have a 2009 iMac 27 and a new rMBP 13" - using a miniDisplayPort cable works great, it switches over right away, and you can close the lid just fine. the screen flicks off and back on quickly when you do it, but then it's fine.

    Also you don't even need an external keyboard, just a mouse will work too - however that doesn't make much sense...but it still works.
  9. jg321 macrumors 6502

    Aug 29, 2012
    As has been said, TDM doesn't change anything, it's the clamshell requirements that determine this, which are power and keyboard/mouse. I use both a cMBP 13" and an rMBP 13" hooked up to a 21.5" late 2013 iMac in this way.

    TDM is great in principle, but has the following drawbacks for me:

    1) Using the iMac kb/mouse on the laptop is a bit of a faff. I'm currently achieving this in a similar manner to the "bash script" at the bottom of http://wherenow.org/imac_target_display_bluetooth_keyboard_mouse/

    2) It's flakey. CMD+F2 often needs to be pressed like 5 times. If the iMac locks itself you have to type your password in blind to press CMD+F2 (or use Screen Sharing). Pulling the cable doesn't help either, screen just stays black. Disabling auto-lock just isn't an option for security reasons.

    Overall, it feels very half-assed and not very "Apple" in my opinion. It should either work properly and efficiently or not be an option.

    Not certain on this one, but I assume this won't stop the physical hardware action of putting the computer to sleep. Could be wrong though, but you're gonna need power/kb/mouse anyway if "docking up", so likely not needed.
  10. jennyp thread starter macrumors 6502

    Oct 27, 2007
    @jg321 - Thanks for those points ... presumably I can just plug in my spare Apple keyboard & mouse into the rMBP to use those whilst displaying on the iMac?
  11. jg321 macrumors 6502

    Aug 29, 2012
    Yeah if you have two sets then you're fine. Trying to share them is a pain though!

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