There has been a lot of talk about Thunderbolt 3 displays like the LG UltraFine 5K, and while it is an impressive display, there are a few things you'll want to know if you’re planning to connect one of these displays to an M1 Mac computer along with a USB-C Alt-Mode or a Thunderbolt 3 docking station.

One thing to understand is that the Thunderbolt 3 connection extends a display using DisplayPort. These displays tend to support USB-C Alt-Mode DisplayPort connections. That works very well for Thunderbolt 3 and USB-C Alt-Mode supporting computers, but issues arise when you connect the display to a DisplayLink-based docking station or display adapter. Currently, there is no way to go from a DisplayLink adapter or dock to a Thunderbolt 3 or Alt-Mode display. While there are Thunderbolt 3 to HDMI/DVI/DP/VGA display cables that can work both ways, they can not do so for DisplayLink devices.

The other side of this scenario comes from display limitations on M1 Mac-based computers. Specifically, M1-based computers can only support one external display connection via Thunderbolt/Alt-Mode. There is no way to extend past one native display using the Thunderbolt/USB4 ports on any M1-based Mac.

If you’ve seen our video showing how you can connect multiple displays to the M1 Mac, you may be asking why this display can’t do the same thing. The way docking stations like the UD-3900PDZ or UD-ULTC4K work, is they have one Alt-Mode connection to the M1 Mac, but the other two display connections are made using DisplayLink over USB. Displaylink connects to the computer’s Central Processing Unit (CPU) using the DisplayLink Manager to process display information and send it via USB 3.0 to the DisplayLink chip to be rendered on the display. This process bypasses the M1 single display capability and allows for more displays to be added. It should be said that while DisplayLink is very powerful for most productivity applications, there are some limitations compared to the Thunderbolt/Alt-Mode connected display.

At this point you may have connected the dots to see why connecting more than one Thunderbolt 3 display, like the LG UltraFine 5K, to an M1 Mac will not work.

  • Most Thunderbolt 3 displays like the LG UltraFine 5K only have a Thunderbolt 3 Input.
  • Mac M1 computers can only extend a single display via Thunderbolt/Alt-Mode
  • Currently, we do not know of a cable that will work to connect a DisplayLink-powered docking station or adaptor to a Thunderbolt/Alt-Mode display.

To put it simply, Thunderbolt 3 displays like the LG UltraFine 5K are excellent monitors, but it would not be worth getting more than one of these if you’re planning to connect them to an M1 Mac.

One setup that we can recommend with the LG UltraFine 5K display, is to add one of our DisplayLink docking stations or display adaptors, this allows extending HDMI, DisplayPort, DVI, or even VGA displays to add more desktop real estate to your M1 Mac.

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