More is not always better, but it’s probably true in terms of screen real estate. The iMac scores a lot of points in that area; one of its biggest strengths being the big, vibrant screen it sports. Even if you don’t use the iMac as your main computer (anymore), you can put that screen to work using the iMac’s Target Display Mode.
Target Display Mode
Realising its potential, Apple first introduced Target Display Mode for the 27″ 2009 iMacs running Mac OS X 10.6.1 or later. As the name implies, TDM allows you to use your iMac as an external monitor for your other supported devices. Depending on the make and model of your iMac and source computer, you can even seed audio to the iMac.
Using your iMac’s other facilities, like the webcam and optical drive, is not supported. The emphasis still lies on the iMac’s display.
While in Target Display Mode, you essentially take away the iMac’s screen (and possibly sound) capacities. The iMac doesn’t have to be rebooted, but continues running its own applications in the background, just hidden for the time being. When you go out of Target Display Mode or put your source computer to sleep, the iMac reclaims its screen and heads off from there.
The idea is to connect the Mini DisplayPorts or Thunderbolt ports of your iMac and your source computer. Because of the differences between Thunderbolt and Mini DisplayPort, compatibility between devices depends on the ports that are available and the cable you use to connect them.
It boils down to this: If you have an old iMac with a DisplayPort, you can use a source device that has either a DisplayPort or a Thunderbolt port as long as you use a DisplayPort cable. However, later iMacs with a Thunderbolt port must be connected with a Thunderbolt source device using a Thunderbolt cable. If that makes your head spin, just look up your iMac in the table below to see what cables and source devices are supported. In all cases, your iMac is expected to be running Mac OS X 10.6.1 or later.
To find out which model you have standing on your desk, click the Apple logo in the top left-corner of your screen, choose About This Mac… then More Info… You’ll can find the model number at the top of the info panel. To find out if your computer has a Mini DisplayPort or Thunderbolt port, go to this same screen and press System Report… If you have a Thunderbolt-equipped computer, it should be listed under Hardware.
Alternatively, look at the icon next to the physical port on your computer. Thunderbolt is marked with a lightning bolt icon, Mini DisplayPort looks similar, but is marked with a square-shaped icon.
The above specifications need to be met to be able to use Target Display Mode and start using your iMac as an external display. Depending on your source device, you might also be able to use the iMac as an audio output device when in Target Display Mode.
If your source device has a Thunderbolt port, audio transmission is supported by default. Some Mini DisplayPort Macs can also output audio. To check, go to Apple > About This Mac… > System Report… and select Audio from the Hardware list in the side bar. If HDMI Output or HDMI/DisplayPort is listed, audio output is supported on that computer. On top of that, you’ll need to make sure you’re using a Mini DisplayPort cable that also supports audio transmission.
What About Connecting Non-Mac Devices?
When presented with a big iMac display, a lot of people would rather connect their Xbox or PlayStation than their MacBook. If you’re wondering if it’s possible to connect a non-Mac device to your iMac, the answer is yes and no.
If you have an older iMac with Mini DisplayPort (27-inch Late 2009, or 27?inch Mid 2010), the answer is yes. Apart from another device equipped with Mini DisplayPort, you can use a third-party adapter to convert HDMI to Mini DisplayPort, like the Kanex XD.
Alas, if you have a newer iMac with Thunderbolt support you need to use a Thunderbolt source, so you won’t be able to use adapters like those mentioned above. Bad luck.
How To Enable Target Display Mode
If you’ve checked the above list for compatibility, and you have a supported cable and source device, going into Target Display Mode is very easy. Just connect the Mini DisplayPort/Thunderbolt ports of both devices with the cable and press cmd+F2 on the iMac. (Apple recommends using the official aluminum Apple keyboard on your iMac, because it can’t guarantee support for other keyboard models.)
You can use your iMac’s speakers (if compatible, see above) like you would any other external speakers. Just go to System Preferences -> Sound -> Output to choose your audio output device.
Once you’re in Target Display Mode, you can use the media and brightness keys to control your iMac’s display and media playback, but the other keys on the keyboard will be disabled. To exit Target Display Mode, just hit cmd+F2 again or disconnect the source computer.
Will you be using your iMac as an external display? Maybe even repurpose a sluggish 2009 iMac as a monitor? Let us know in the comments below the article!