HT204592: Use your iMac as a display with Target Display Mode

Learn about Use your iMac as a display with Target Display Mode
gshukill
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Q: Sleep / Dim Displays more than 30 seconds, TDM iMac doesn't wake up

I have two iMacs connected via Thunderbolt. Things work great, except when the main iMac goes to sleep or dims the displays for more than 30 seconds. In those instances, the TDM iMac does not automatically wake up and I'm forced to hit Cmd+F2 again. When it does wake up, I have to hit Cmd+F2 to get it back into TDM.  Any suggestions?

 

I'd like to use the 2nd iMac as primarily a monitor; hitting Cmd+F2 is a nuisance everytime I return to my desk.  MUCH worse, it moves all my windows form the iMac in TDM to the main window.

 

Thanks.

iMac, OS X Yosemite (10.10.3)

Posted on Jun 4, 2015 10:36 AM

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gshukill

Q: Sleep / Dim Displays more than 30 seconds, TDM iMac doesn't wake up

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  • by Nubz N.,

    Nubz N. Nubz N. Jun 6, 2015 10:33 AM in response to gshukill
    Community Hosts
    Jun 6, 2015 10:33 AM in response to gshukill

    Hello gshukill,

     

    I'm not sure how your main iMac is going to sleep but the behavior of the external display iMac depends on how the main iMac is sleeping.

     

    OS X Yosemite: Use another Mac as a display

    Learn what happens when the primary Mac goes to sleep and wakes up

    The external display Mac behaves differently depending on how the primary Mac goes to sleep.

    • If you put the primary Mac to sleep: After you put your Mac to sleep, the external display Mac goes dark for a few seconds and then displays the windows for its own apps. If the external display Mac does not display the windows for its own apps, press Command (⌘)-F2 on its keyboard.
    • If the primary Mac goes to sleep because it was idle: The external display Mac goes dark and stays dark. If you want the external display Mac to display the windows for its own apps, press Command (⌘)-F2 on its keyboard.

     

    If the external display Mac doesn’t show the right desktop after it wakes up: When the primary Mac wakes up, the external display Mac displays the windows for the apps on the primary Mac. If it does not, press Command (⌘)-F2 on the keyboard of the external display Mac.

    There's another article that states that sleeping either computer exits TDM.

     

    Target Display Mode: Frequently Asked Questions (FAQ) - Apple Support

    How do I exit TDM?

     

    To leave TDM, press Command-F2 on the keyboard of the iMac that is in TDM. You can also exit TDM if you shutdown or sleep either computer or detach the cable. 

    That would explain the need to re-enable TDM when the computer wakes up.

     

    If you aren't sleeping them for long maybe a screensaver would be a workaround.

     

    Thank you for visiting Apple Support Communities.

    Nubz