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connect 3 monitors to a new

Have just bought the latest iMac (1TB) and have a Thunderbolt Display screen as a second monitor.

Can I use my old 2015 iMac as a third monitor screen?

the new iMac has two Thunderbolt ports, and the old IMac also has a Thunderbolt port. To connect the two do I just need a thunderbolt cable with an adaptor to make this work?

Posted on Oct 25, 2021 1:33 PM

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Question marked as Top-ranking reply

Posted on Oct 25, 2021 2:43 PM

If you're using a Mac with Apple silicon:


  • You can connect one external display to your Mac using either of the
  • Thunderbolt / USB 4 ports. On iMac and Mac mini, connect your display
  • to either of the ports with the Thunderbolt symbol .
  • On Mac mini (M1, 2020), you can connect a second display to the HDMI port.
  • Using docks or daisy chaining devices doesn't increase the number of displays you can connect.


8 replies
Question marked as Top-ranking reply

Oct 25, 2021 2:43 PM in response to DurksD

If you're using a Mac with Apple silicon:


  • You can connect one external display to your Mac using either of the
  • Thunderbolt / USB 4 ports. On iMac and Mac mini, connect your display
  • to either of the ports with the Thunderbolt symbol .
  • On Mac mini (M1, 2020), you can connect a second display to the HDMI port.
  • Using docks or daisy chaining devices doesn't increase the number of displays you can connect.


Oct 25, 2021 3:12 PM in response to Mal-S

Thank you. I’m still perplexed as to why there would be two thunderbolt ports in the iMac if only one additional display can be used?

As you can tell, I’m pretty low on technical knowledge.

is a 24” iMac M1 with 2 x thunderbolt ports and 2 x usb 3 ports.

I was hoping to connect a display in each thunderbolt port.

Oct 25, 2021 3:23 PM in response to DurksD

The ports are primarily for connecting devices such as external drives. It is not the number of ports which determines the number of monitors it is the hardware, which in the case of the M1(Apple Silicon) Macs is two (includes the internal monitor of iMac and MacBooks) the Mac mini doesn't have a built-in monitor hence the additional HDMI port. Who knows, when Apple expands their chip designs in the future they may make an Apple Silicon Mac which supports more monitors, we wait and see.

Oct 26, 2021 1:48 AM in response to Mal-S

Hi Mal-S

I've found this online which suggests that it is possible to connect 3 (Dell) monitors.

https://youtu.be/u0GbrZVDXLk

I'd be grateful for your thoughts please as it appears to support 3 screens via a different connector.

Though I think I'd still need to buy an additional thunderbolt cable plus an adaptor to use my 2015 iMac as an extra screen? Which would be an expensive experiment!

All the best for now David


Oct 26, 2021 3:32 AM in response to DurksD

Hi Mal-S. I've now found the information you kindly showed me about Apple Silicon so I'm restricted to one display though have just connected my iPad using 'sidecar' which gives me an (albeit) smaller third screen view of my calendar & 'to do' lists.

I'm also going to try using my old iMac just for one single application, either e-mails or diary as they update across all my devices.

Thanks for sharing your views and information which has helped me progress my thinking to this point, and avoided buying another thunderbolt cable & adaptor unnecessarily.

Kind regards David

connect 3 monitors to a new

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