2 Replies Latest reply: Jan 9, 2014 8:48 AM by varjak paw
Aragorn Castela Level 1 (0 points)


I'm trying to connect an iMac, late 2009 model, to a retina display laptop via mini display port cable to use it as a screen. The problem is once I connect the two computers and press coomand fn f2 the screen on the laptop goes blue and it goes black on the iMac just for a few seconds and then it goes back to normal.

Also when i press the alt key i see the "detect desplays" button in the system prefrecens but I can't press it.

I have to add that I have connected my cinema display to same laptop and it work fine. I just can't see a reason why it soulhdn't work with iMac.


Any suggestions are very much appreciated.




iMac, OS X Mavericks (10.9.1)
  • sterling r Community Specialists (6,590 points)

    Hello Aragorn,


    It sounds like you are unable to set your iMac to be in Target Display Mode as expected. I wanted to recommend these troubleshooting steps specifically from the article named:

    Apple computers: Troubleshooting issues with video on internal or external displays



    No video or no signal, image distortion, "snow," or flickering

    Check connections

    When using an external display be sure to check the following:

    1. If you're using an Apple notebook, confirm the AC power cable or adapter is securely connected to the computer and the cable providing power to the display is also secure. It is always good to have your notebook connected to AC power when an external display is in use.
    2. Confirm display adapters are fully seated in their respective connections and that they are supported models and for the computer and display. Refer to these articles to assist you with adapter compatibility and further configuration information:
    3. Remove all display cable extenders, KVM switches, or other like devices and retest to determine if the issue is resolved.
    4. Try unplugging the video adapter or cable and then plug it back in.
    5. If more than one video adapter is in use (or "daisy-chained"), troubleshoot by using only one adapter.
      • Example: A mini DisplayPort to DVI adapter connected to a DVI to HDMI adapter is an unsupported configuration because there is a series of adapters in use.
    6. If available, try using a different display and or adapter (or use a different connector by using DVI instead of VGA, for instance).

    Reset the systemYou can reset the Mac's parameter RAM and SMC.Reset the resolutionStart by resetting the Mac's parameter RAM. If the display does not come up, was previously set to an unsupported resolution, and still results in no video:

    1. Start up in Safe Mode.
    2. From the Apple () menu, choose System Preferences.
    3. Choose Displays from the View menu to open the preferences pane.
    4. Select any resolution and refresh rate that your display supports.
    5. Restart your computer.


    Thank you for using Apple Support Communities.

    All the very best,


  • varjak paw Level 10 (169,815 points)

    sterling r wrote:


    Hello Aragorn,


    It sounds like you are unable to set your iMac to be in Target Disk Mode as expected.


    Sterling, I believe you meant "Target Display Mode", yes? Just to avoid confusion.


    I would also suggest that we determine which specific model of Macs the poster has before we suggest a long list of troubleshooting steps. This support article might be the best one to begin with, if for not other reason than to verify that the specific Macs will work in Target Display Mode as intended: