I have a new 2019 MacBook Pro 15”. I would like to use my old 27” iMac (late 2009) as an external display. What do I have to do? I’ve found instructions for using a mini DisplayPort out to the iMac, but the new MacBook Pro doesn’t have that. Thx.
MacBook
Your 2019 MacBook Pro should have Thunderbolt 3/USB-C ports. As such, you will need to use a Thunderbolt 3 (USB-C) to Thunderbolt 2 adapter. Then use a Mini DisplayPort cable to connect to the Thunderbolt 2 end of the adapter.
Your 2019 MacBook Pro should have Thunderbolt 3/USB-C ports. As such, you will need to use a Thunderbolt 3 (USB-C) to Thunderbolt 2 adapter. Then use a Mini DisplayPort cable to connect to the Thunderbolt 2 end of the adapter.
Note: Target Display Mode isn’t supported on iMac models with Retina display. Only iMac (27-inch, Late 2009), iMac (27-inch, Mid 2010), and iMac (Mid 2011 to Mid 2014) support Target Display Mode.
So you'll need a USB-C to MDP cable, or combo like mentioned.
Use a iMac late 2009 27 as external display for new MacBook Pro
