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I'm trying to use my old mid 2011 iMac (High Sierra) as display for my 2017 Macbook Pro (Catalina), using a Thunderbolt 3 to Thunderbolt 2 adapter and Thunderbolt cable. But after pressing Command + F2 nothing happens, even after restarting both computers. Anyone know the reason for this?
First questionI guess does the iMac show as a connected Thunderbolt device
in System Information on the MacBook Pro?
If it is not showing up there, it could be that you have a bad cable
or a bad adapter.
Also, as an additional check, in the same setup see if you can
connect in Target Disk Mode?
Transfer files between two Mac computers using target disk mode - Apple Support
This will give us an idea whether there is a fundamental Thunderbolt issue
if it doesn't work or some graphics issue if it does or Thunderbolt hardware issue.
First questionI guess does the iMac show as a connected Thunderbolt device
in System Information on the MacBook Pro?
If it is not showing up there, it could be that you have a bad cable
or a bad adapter.
Also, as an additional check, in the same setup see if you can
connect in Target Disk Mode?
Transfer files between two Mac computers using target disk mode - Apple Support
This will give us an idea whether there is a fundamental Thunderbolt issue
if it doesn't work or some graphics issue if it does or Thunderbolt hardware issue.
Use your iMac as a display with target display mode - Apple Support
Am I reading this right?
Target display mode requires macOS High Sierra or earlier. It does not work with macOS Mojave or later.
I wasn't aware Apple killed TDM in later versions.
To the OP...have you tried Command-Fn-F2 instead of Command-F2?
Seems it doesn't show up on system information, but I could connect them in Target Disk Mode. So I doubt it's the cable or adapter, as both are brand new. I suspect it's the iMac but not sure what the actual issue is?
For Graphics/Displays it lists "Intel HD Graphics 630" and "Radeon Pro 555".
Yeah doesn't change at all. I also tried launching both in Safe Mode and in that case there's a slight flash when I press command+F2, but nothing else.
The iMac is 21.5-inch, Mid 2011.
On my 2011 iMac with no TB cable connected I get no result using CMD+F2, so could it be the cable?
If target display mode doesn't work
If your iMac doesn't show the desktop of your other Mac, try these steps first:
Restart your iMac.
Restart the other Mac.
Unplug the Thunderbolt or Mini DisplayPort cable from the other Mac, then plug it back in.
Press Command-F2 on the iMac.
If that doesn't work, try these other solutions:
If you're currently logged in to the iMac that you want to use as a display, choose Apple menu > Log Out to return to the login window. Then press Command-F2 again.
Choose Apple menu > System Preferences, then click Keyboard. If ”Use F1, F2, etc. keys as standard function keys” is selected, target display mode uses Command-Fn-F2 instead of Command-F2. It might also help to use the keyboard that came with your iMac. Some third-party keyboards and older Apple keyboards don't support target display mode.
Make sure that your iMac is using macOS High Sierra 10.13.6 or earlier. You can't use target display mode with later versions of macOS, or with Boot Camp and Windows.
Please disconnect all the connections and then restart both computers with a NVRAM reset per the directions in NVRAM Reset and then re-connect and re-test.
actually it does now for some reason say device connected, just not "iMac"
Just checking, you're using Command + F2 on the older iMac?
Might require an MDP cable... Mini Display Port.
Yeah on the old one. Hmm I was told thunderbolt was the way to go. Thoughts on any other solutions...?
Good shout, tried this on both but didn't work unfortunately! Any other ideas?
But I'd think that requirement would apply to the Target Mac that is to appear as a Monitor to the other Mac!?
But I haven't heard back from anyone in this situation yet.
I also assumed that requirement was applied to the target Mac, but not sure...! And yeah I've tried both, on different keyboards.
On your System Info on the MBP what does it say for Graphics/Displays?
iMac's screen doesn't change using the key combos?
The iMac is a 27" 2011 right?
Using iMac as external display not working
