Can a USB-C to mini DisplayPort cable be used with USB-C to Thunderbolt ports? I have the above cable for my current set up of sending display from my PC laptop with a USB-C port to my 2010 iMac with a mini DisplayPort port. It works great.
I have now bought a mid-2011 iMac that does not have a mDP port. It has a Thunderbolt port. Which I guess is Thunderbolt 2.
The current cable is not working with this new set up (even though it will plug into the Thunderbolt port) and I cannot work out if the problem is trying to use the cable itself or if I am not setting it up properly.
So do I need a different cable if the only thing that is changing in the configuration is that instead of a mini DisplayPort on the iMac, I have Thunderbolt port on the iMac.
From other answers I think I might need a different cable but I still can’t quite work out what, or if I need one of those very expensive apple adapters.
Here are some basic rules about Thunderbolt and DisplayPort cables:

Any Type C Thunderbolt 3 cable is also a USB-C cable.  Only quality USB-C cables are also Thunderbolt 3 cables.  In other words, avoid cheap ones.

Thunderbolt 1 and Thunderbolt 2 cables, while they carry the mDP signal are not mini DisplayPort cables.  mDP cables are not Thunderbolt cables and vice versa.

Thunderbolt cables can only be used on Thunderbolt ports.

mDP cables can be used in either mDP ports or Thunderbolt ports


Source:  TrippLite.com



So do I need a different cable if the only thing that is changing in the configuration is that instead of a mini DisplayPort on the iMac, I have Thunderbolt port on the iMac.

Yes.  The 2011 iMac (27&quot; only) support Target Display Mode via Thunderbolt only.  You will need the following:

Thunderbolt 1/2 cable
Thunderbolt 3 to Legacy Thunderbolt Adapter

The 2011 iMac is a very different animal compared to the 2010 that uses DisplayPort.  To connect to it via Target Disk Mode, it requires a TB connection. So you'll need a proper adapter and cable to make this work.