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Having Problem Dual Screening Late 2009 iMac to Late 2015 iMac  



I have read tried and failed to dual screen my 2 iMacs

In the late 2009 I have an mini display port to HDMI cable (male)

In the late 2015 I have a thunderbolt 2 to HDMI cable (female)

Command F2 does not seem to work on either screen

Please help

3 Answers

Firstly check that your old iMac is a model that supports target display. My reading of this page is that only the 27” 2009 model is suitable. 

Next.... this definitely won’t work if you’re running a series of connections through HDMI. It must be a proper thunderbolt connection. 

And.... the command F2 is performed on the old Mac that you wish to be the “slave”.  I always think of saying “I command you to be a slave” to remember which one.


Tx Graham - both iMacs late 2009 and 2015 are 27" so should be good there.
So fault seems that I must find a mini display port to a Bolt 2 port and not via HDMI - I will buy one and let you know


Says: 27" 2009 iMac.

Says: Target display mode requires macOS High Sierra or earlier on the iMac used as the external display. It does not work with macOS Mojave or later.

If the above 2 are true, I would use a miniDisplayPort-to-miniDisplayPort cable between the 2 Macs.  A Thunderbolt 2 port is also a miniDisplayPort, so you just plug directly into the miniDisplayPort on the 2009 and the TB2 port on the 2015.

When I had a 27" 2009 iMac I successfully used Target Display Mode using that cable from the 2009 to a 2011 15" Macbook Pro with Thunderbolt 2 ports.  So I know that will work.

In my opinion you are using way too many adapters for your approach.  Just a simple mDP-to-mDP cable should be all you need.


Ok - re-boot back High Sierra - if that is possible and change the cable - many tx