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I have the following set-up:

  1. Laptop with:
    • USB-C with Thunderbolt 3
    • HDMI
  2. Monitor 1 with:
    • USB-C
    • DP in and out (with MST support)
    • HDMI
  3. Monitor 2 with:
    • HDMI

Currently I have my first monitor connected via USB-C, and my second monitor via HDMI. I'm considering two options to connect the two monitors using only a single connector to my laptop. The first option is to simply buy a USB-C to dual HDMI (plus optional USB-C PD) hub, connect both monitors using HDMI and connect the hub using USB-C.

Would it also be possible to link the HDMI port of monitor 2 to the DP port of monitor 1, and then use the USB-C cable from Monitor 1 to my laptop, or would that only work if I also used the DP out from monitor 1?

So, in essence: would it work to buy a DP to HDMI cable to complete this setup, is the hub the only viable solution, or is there yet another way I'm overlooking?

EDIT: I'm aiming for Full HD 1080p resolution on both screens with a refresh rate of 60Hz

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  • You have in/out switched entirely. // DisplayPort over USB-C often has limited bandwidth to allow for USB 3.0 alongside it. You don’t mention any display resolutions and refresh rates you want to achieve.
    – Daniel B
    Commented Aug 23, 2021 at 10:17
  • Not aiming for spectecular resolutions / refresh rates, I've edited my post to include them
    – konewka
    Commented Aug 23, 2021 at 11:00

1 Answer 1

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With DisplayPort over USB-C, there is an important limitation to be aware of. Unlike with Thunderbolt, the USB and DisplayPort signals are not muxed and each requires dedicated wires. This means the following configurations are possible:

  • 1 DP Lane + SuperSpeed USB
  • 2 DP Lanes + SuperSpeed USB
  • 4 DP Lanes + High Speed USB

In many adapters/hubs/docks, you don’t get to select the configuration. It’s typically 2 DP Lanes + SuperSpeed USB. I’m aware of one adapter from StarTech (DK30C2DAGPD) that has a switch to select the configuration.

Depending on the DisplayPort version, a lane has more or less bandwidth. Starting from DisplayPort 1.2, one lane offers enough bandwidth for 1080p60. If the display uses lanes accordingly, you can connect two 1080p60 displays to one DisplayPort over USB-C output.

Your display’s DP-out will most likely not be a DP++ output. As such, you need an active DP-to-HDMI converter. It may be easier to get an integrated MST hub + dual HDMI converter. Getting one that works may be a little hit-or-miss though.

Apple MacBooks apparently have limitations regarding MST so all this may not work. I haven’t confirmed this myself though.

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