Target Display Mode iMac mid 2011

This is demonstrating a 2009 iMac with a new iMac, which does work.

You have a 2011 iMac with a new iMac, and that does not work.

2009 and 2011 iMacs use different methods for TDM. That's why it works in the post, but it won't for you.

Cheers,

Jack

+1 on Jack-19's response.

To add to Jack's information, others have not been able to make that work even on 2009 and 2010 iMacs. Also the poster was using Catalina, not Big Sur. An Apple employee tested and confined from me that Big Sur does not support TDM.

TDM is now totally unsupported technology. Apple started the deprecation of TDM over six years ago by removing its capability starting with Late 2014 iMacs, and threw the last shovel of dirt in tis face in early 2020. They even archived the support article in Early 2020. It won't see further edit or updates.

The cost of MDP cabling alone could buy you a nice used DP monitor at the thrift store. The cost of a Thunderbolt 3 cable and adapter you would need for a 2020 Mac will buy you a new FP monitor on sale.

Hi PaoloFrega,

Unfortunately, the 2020 iMacs are not compatible with Target Display Mode. It won't work, sorry.

Cheers,

Jack

Anytime!