User profile for user: i-am-nick
i-am-nick Author
User level: Level 1
6 points

Command F2 does nothing

Hi,


I've been wrecking my head trying to get my late 2012 21.5 inch iMac to work as an external display for either my Windows laptop or Macbook Pro (2010).


My problem is that I can't get my iMac in to Target Display Mode. When I press Command+F2 nothing happens...at all...


I've gone through all of the recommendations e.g. trying on the login screen, trying when logged in, checking the keyboard settings, pressing Command+Fn+F2, restarting, unplugging the cable, etc. etc. etc.


I've ruled the keyboard out as the problem as I see this in the system.log when hitting Command+F2:

Apr 24 11:54:35 The-Mothership dpd[943]: objc[943]: __NSFrozenArrayM object 0x7f8b2fc12ac0 overreleased while already deallocating; break on objc_overrelease_during_dealloc_error to debug



Does the display need to detect a video input before it'll try entering Target Display Mode perhaps?


Any help is really appreciated.


Thanks in advance.

iMac 21.5", macOS 10.15

Posted on Apr 24, 2020 4:00 AM

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User profile for user: Allan Jones
Allan Jones
User level: Level 9
74,066 points

Posted on Apr 24, 2020 10:29 AM

Have you been through this Apple article:


Use your iMac as a display - Apple Support


...trying to get my late 2012 21.5 inch iMac to work as an external display for either my Windows laptop...


Target Display Mode was never intended to work with non-Apple devices. Sometimes someone gets it to work but its is technically unsupported.

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User profile for user: Allan Jones
Allan Jones
User level: Level 9
74,066 points

Apr 24, 2020 10:29 AM in response to i-am-nick

Have you been through this Apple article:


Use your iMac as a display - Apple Support


...trying to get my late 2012 21.5 inch iMac to work as an external display for either my Windows laptop...


Target Display Mode was never intended to work with non-Apple devices. Sometimes someone gets it to work but its is technically unsupported.

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User profile for user: Malcolm J. Rayfield
Malcolm J. Rayfield
User level: Level 7
23,077 points

Apr 24, 2020 6:30 PM in response to i-am-nick

Use your iMac as a display with target display mode - Apple Support

It won't work if the iMac is running Mojave or Catalina. You would need to downgrade it to High Sierra.

Are you using a Thunderbolt cable.

https://www.apple.com/shop/product/MD861LL/A/apple-thunderbolt-cable-20-m

It won't work with a Mini DisplayPort cable, even though the plugs will fit.


Does the Windows laptop have Thunderbolt ports (lightning bolt icon next to the port)?

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User profile for user: i-am-nick
i-am-nick Author
User level: Level 1
6 points

May 4, 2020 11:16 PM in response to Malcolm J. Rayfield

My laptop doesn't have a thunderbolt port, only a USB-C which supports DisplayPort Alt Mode. I read somewhere that the iMacs with Thunderbolt 2 ports should still accept a DisplayPort signal.


I purchased a Thunderbolt 3 to Thunderbolt 2 adapter but I don't think my laptop is recognising it as a device to use DisplayPort Alt Mode with, although it is recognising it as a USB device as a "Legacy Adapter". I'm connected between the adapter and my iMac with a Thunderbolt 2 cable but still nothing.


Should I be looking to get a USB-C to Mini DisplayPort adapter instead? Would a Thunderbolt 2 cable still work?


To clarify, this is my setup:


Windows 10 Dell laptop with USB-C port (supports DP Alt Mode)

iMac with Thunderbolt 2 port


As per this article, TDM is supported by the version of Catalina I'm on (10.15) https://support.apple.com/en-ie/guide/mac-help/mh30822/mac

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User profile for user: rcprado
rcprado
User level: Level 1
51 points

May 4, 2020 11:39 PM in response to i-am-nick

There is a How to by Apple here

https://support.apple.com/guide/mac-help/use-an-imac-as-a-display-mh30822/10.14/mac/10.14


It is supposed to work, up to Catalina, as per Apple Docs


But first, considering you have both the iMac and the MacBook, forget windows at first (for a moment) and folow the instructions to make it work using MacOS (iMac + macbook) and once you get it working, then try with windows.


Why? because there may be any situations with cables, DisplayPort, Adapters, etc


I would try first using MacOS on both, than once adaptors and cables and ports were fine and functioning, I would try via Windows..


Techinically [by documentation] you can make it work for sure

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User profile for user: Malcolm J. Rayfield
Malcolm J. Rayfield
User level: Level 7
23,077 points

May 5, 2020 12:54 AM in response to i-am-nick

The 2011 iMac has Thunderbolt ports. These ports can output Mini DisplayPort video to connected displays, but when the iMac is being used as a display it needs Thunderbolt coming in. The 2009 and 2010 iMacs used Mini DisplayPort both in and out, but the 2011 requires Thunderbolt for input.


Your 2010 MabBook Pro has Mini DisplayPort, not Thunderbolt, so there is no way for it to use a 2011 iMac as a display.

If the Dell laptop has Thunderbolt 3 (lightning bolt icon next to the port), not just USB-C, it might work with a Thunderbolt adapter and cable, but if not, no adapters will help.

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Command F2 does nothing

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