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I have a 2017 Macbook Pro connected to an HP Thunderbolt hub. From that hub, I have two USB-C -> DVI cables going into two monitors. For my third monitor, I have a DisplayPort cable from the hub to the monitor.

The two DVI monitors work correctly and show up in System Preferences > Displays > Arrangement. The third monitor (the DisplayPort one) does not show up in the displays. Additionally, it is always mirroring one of my DVI monitors.

What's interesting is that if I unplug one of the DVI monitors, the third monitor starts working correctly and shows up in the Arrangement tab.

Is it not possible to have 3 monitors running where two are DVI and one is DP?


Edit: The resolutions of the two monitors using DVI are 1920 x 1080 and the resolution of the monitor using DP is 2560 x 1440.

3

The problem with your setup does not have to do with the resolution, as others have hypothesized. The problem is that the dock you're using is not supported on macOS for a 3-display configuration.

In practice, the HP Thunderbolt docks require MST-support for multiple displays from the system before they can enable 3 separate displays connected to the dock. MST is not supported on macOS for this purpose(in contrast to Windows), as thus it simply won't work.

You can connect two of the displays to the dock (as you have already figured out). The third display you'll need to connect directly to the MacBook Pro in order to get it as a separate display.

  • Got it, thanks a lot. I'll try it out and see if it works! – saadq Aug 29 '19 at 21:02
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As shown on Apple's website, there is a restriction on the number of monitors that can be used at the same time. If you want a more specific answer, could you post the resolutions of your monitors.

  • Up to two displays with 5120-by-2880 resolution at 60Hz at over a billion colors.
  • Up to four displays with 4096-by-2304 resolution at 60Hz at millions of colors.
  • Up to four displays with 3840-by-2160 resolution at 60Hz at over a billion colors.

Additionally, it is possible (yet very unlikely) that your MacBook could not supply enough power to send all those bytes to your monitors (especially if you have other peripherals plugged in to your MacBook)

  • Edited question to include resolutions, basically two monitors are 1920 x 1080 and one is 2560 x 1440. – saadq Aug 29 '19 at 20:43
  • @saadq What size is your MacBook's screen (13.3" or 15")? – ds_secret Aug 29 '19 at 20:54
  • It is 13.3". I am going to try out the other answer though. – saadq Aug 29 '19 at 21:01
  • Ahh, unfortunately there seems to be a different issue now. So now, I have 1 usb c -> DisplayPort going from my laptop to the third monitor and I have the same 2 usb-c -> DVI from the hub going to the other monitors. Now, only one of the DVI monitors can be on at once. The other one will only turn on if I unplug the other DVI monitor, and vice-versa. :/ – saadq Sep 4 '19 at 22:47

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