How many displays on a single USB4 connection (FW13 AMD 7040)?

Framework Laptop 13
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1

Hello,

I have 3 screen on my desk :

  • 1 ultra wide Dell U4025QW - 5120x2160 @ 60 Hz - main display
  • 1 small ultra wide Asus PA147CDV - 1920x550 @ 60 Hz
  • 1 small Magedok T089B - 1920*1200 @ 60 Hz

The Dell display is certified Thunderbolt 4, with daisy chaining possible.

I also have a Caldigit Element Hub 5.

I tried different setups:

  • FW13 (rear left port, USB4) –> Dell U4025QW –> Caldigit Element Hub 5 (Thunderbolt ports of the hub) –> Magedok + Asus displays
  • FW13 (rear left port, USB4) –> Caldigit Element Hub 5 (Thunderbolt ports of the hub) –> Magedok, Asus & Dell displays

No matter what, I could only get two displays out of three working.

When I tried this setup :

  • FW13 (rear left port, USB4) –> Dell U4025QW

    FW13 (rear right port, USB4) –> Caldigit Element Hub 5 (Thunderbolt ports of the hub) –> Magedok, Asus displays

All three displays worked !

Is there a limitation on the number of displays streams that I can get over a single USB4 port ?

In case it matters : Fedora Linux 42 on KDE Plasma 6

2

There are certainly bandwidth limitations. As far as I can find, TB4 may be able to handle dual 4K max and your Dell ultrawide is more than standard 4K. So I wouldn’t be surprised if there are problems negotiating two more monitor signals through the same connections (even though they are not so super high res).

It’s nice that when split between two interfaces, they all work! I’d expect that as soon as you throw a 4K in the mix, it’s going to be tight for the rest.

You could try and see if you can get them all running through a single connector by setting a lower resolution (are they even recognized if you chain them together?)

1 Like
3

When there are 3 monitors on the same USB4 port, 2 out of 3 are recognized.

I don’t even get a chance to lower the resolution, the third monitor is not shown in the Display Settings of KDE.

Unplugging the second monitor makes the third one to appear…

4

What interface/port you’re using for the displays? HDMI? DisplayPort? Both?

I’ve had issues when I was running both HDMI and DisplayPort.