U3417W, Windows 11, MST from USB-C source

Question

I've had these two U3417W for a while and was working off a MacBook Pro, which did not support MST.

I'm now primarily working off a Windows computer, and when reorganizing my desk this weekend, was excited by the possibility of being able to daisy chain my two U3417W.

I've got a USB-C to DP cable running to U3417W 1, then the provided DP to mDP cable from U3417W 1 to U3417W 2. I've enabled DP1.2 on both U3417W (I think. The menu doesn't quite work as indicated in the instructions), and turned MST on U3417W 1 ON (MST on U3417W 2 is off, I had to connect it directly to get the menu, but I did check!)

U3417W 2 doesn't display anything at all. U3417W 1 works as expected. But the weird part is that U3417W 2 DOES recognize it has something plugged in (it displays the "No image on this input" message, not the "No mDP Cable" message).

The computer recognizes there are two external U3417W hooked up, in Dell Display Manager as well as System display settings.

It feels like I'm SO close to getting this working. But I have to work tomorrow and if it's not a quick fix, I'll just go back to two separate outputs, one to each U3417W.

hdsheena · Answer

In the interest of troubleshooting, I reversed the monitors, and the image showed up on both (but the computer only recognizes a single display). Then I enabled MST on Monitor 2 (now the one directly connected to the computer), and Monitor 1 went blank with the "No mDP signal from your device" message.

I thought the computer wasn't recognizing the second monitor in this config, but when I changed the system settings to "Extend" vs "mirror", it seemed to find the other one, so it's the same as in the first configuration now.

DELL-Chris M · Answer

Is the Windows PC a Desktop or Laptop? If a Laptop, is the Laptop power adapter attached?

The online U3417W User's Guide for these 2017 released U3417W monitors does not specifically show dual DP MST setup using a PC source USB-C. It shows the PC source as DP out port. But in theory using PC source USB-C out to #1 U3415W DP in port could work.

hdsheena · Answer

Laptop, and yes to power supply. The fact that the computer recognizes the third display (native, plus monitors 1 and 2) is what gives me hope but the lack of picture is obviously not going to help.

hdsheena · Answer

Is there a specific cable I need? The one I have, I'm pretty sure it said it supported MST, but it's not any official brand. Or should I just give up?

Monitors

U3417W, Windows 11, MST from USB-C source

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