Q: Connecting MacBook Pro Retina with iMac Retina

Hello ,

Thanks for using Apple Support Communities.

The iMac Retina 5K does not support Target Display Mode, which is the feature to use an iMac as an external display.  Below are the requirements for Target Display Mode:

 

 

What are the requirements for TDM?

• A Mac notebook or desktop with a Mini DisplayPort or Thunderbolt connection
• A Thunderbolt or Mini DisplayPort cable  
• A supported iMac with OS X 10.6.1 or later. The table below shows iMac computers that support TDM, the required cables, and the port of the computer to which you are connecting the iMac.

                          

iMac Model	Cable Supported	Port on Source Computer
iMac (27-inch Late 2009)	Mini DisplayPort to Mini DisplayPort	Mini DisplayPort or Thunderbolt
iMac (27-inch Mid 2010)	Mini DisplayPort to Mini DisplayPort	Mini DisplayPort or Thunderbolt
iMac (Mid 2011)	Thunderbolt to Thunderbolt	Thunderbolt
iMac (Mid 2012 and later)	Thunderbolt to Thunderbolt	Thunderbolt

Note that the iMac (Retina 5K, 27-inch, Late 2014) does not support Target Display Mode. 

 

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

Take care,

Alex H.