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I have two modern monitors:

  • Huawei MateView 28" (3849 x 2560)
  • Dell P2423DE 23.8" (2560 x 1440)

They are arranged as depicted below:

enter image description here

Currently I'm using a Lenovo Thinkpad T490 and a Dell XPS 9550 (from 2016). Both have USB-C output.

I was hoping to be able to use MST connecting only a USB-C from computer to the Dell monitor and then the DP out from the Dell monitor to the Huawei monitor. However, that makes the image quality of the Huawei very poor. The only way I have been able to connect both monitors to one computer is to use both USB-C outputs of the Lenovo computer, one to each monitor. That wouldn't work for the Dell computer since I only have one USB-C output there.

The ideal setup would be to only need to connect a single USB-C output from my computer (handling both energy, monitors and the USB-stuff connected to the monitors). How would I do this?

Edit 1: I was hoping a dock would not be needed since I chose the monitors with many USB ports so that they themselves could work as docks, reducing the number of devices. Also one reason for going with P2423DE was the 90W charging using USB. But maybe the built-in docks of these monitors are not powerful enough? If I need a dock: Do you know which performance (or specific device) I should look for? Would the Dell computer USB-C throughput be suffi

Edit 2: I have also tried connecting the computer USB-C to a monitor USB-C and then the monitor USB "output" to the other monitor USB-C input, but that never gets any display from the second monitor (but the keyboards etc connected to the second monitor is accessible by the computer). I guess the throughput isn't enough for display?

Edit 3: One of the USB-C ports of the Lenovo is TB3 and so is the only USB-C port of the Dell. The Dell computer is old and I have seen people experience challenges with the behavior of the TB3 port. However, based on the input from Tom Yan I tested whether the following setup would give better result. Lenovo TB3 to Dell monitor USB-C and Dell monitor DP out to Huawei DP. This didn't give any better result than using the Lenovo USB-C (gen 1) output.

nize
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    Can you be more specific on "poor image quality"? Do you mean like you are only allowed to choose a resolution of ~720p? From what I can see in the spec of your laptop, the port supports up to DP 1.2 (i.e. HBR2), so at 60Hz you probably can't get much more than 2160p + 720p anyway. You might be able to use the optimal resolution on both screens if they support displaying at 30Hz (or 24Hz, which might be slightly more common for PC screens). – Tom Yan May 13 '22 at 16:32
  • Instead of a dock (which I doubt that would help), you may also consider using a DisplayLink adapter for the secondary screen. – Tom Yan May 13 '22 at 16:35
  • @TomYan I guess you are on to something regarding the limited throughput of the computer ports. I see in https://psref.lenovo.com/syspool/Sys/PDF/ThinkPad/ThinkPad_T490/ThinkPad_T490_Spec.PDF that DP 1.2 is supported for the Lenovo. I didn't know that wasn't sufficient for driving the resolutions I want at a decent freq. So the conclusion is I need to use two ports of the laptop for full resolution and freq? A dock would not help me? – nize May 13 '22 at 16:44
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    I'd say so (but it's purely theory; I'm not very experienced in this). Btw doesn't the Dell one have an extra HDMI port? Can't you use that? – Tom Yan May 13 '22 at 16:49
  • @TomYan Regarding DisplayLink and HDMI: Given your input of the DP 1.2 limitation, I guess one of the monitors will be connected using USB-C to USB-C. For the second connection there are more alternatives: 1) Thunderbolt to USB-C, 2) Thunderbolt to DisplayPort, 3) HDMI to HDMI. Alt 1 and 2 would only work for the Lenovo laptop. Alt 3 would work for both laptops. However, for alt 3 I wouldn't get the signal from USB stuff connected to that monitor? Also, there is no benefit of using the DisplayLink I guess? – nize May 13 '22 at 16:57
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    Ah, now that you mentioned TB(3). It seems that with TB3 you can get like HBR2 x 2 (out of one port). So a *TB3 dock* (but not a *USB-C dock*) *might* (I have no idea whether that is guaranteed on every TB3 port) fulfill what you need. And yeah with HDMI you won't get any "extras". And unless there's specific reason that you can't use the HDMI port, I don't see any point to use a DisplayLink adapter instead. – Tom Yan May 13 '22 at 17:15
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    Instead of a multi-purpose dock, you might want to consider [this](https://www.amazon.com/dp/B08KFMBQ21) too. – Tom Yan May 13 '22 at 17:21
  • Thanks on the TB3 dock ideas. However, I don't fully trust my old Dell laptop TB3 port, and I believe I'll get an HDMI cable and test using the following setup: Laptop USB-C to Huawei USB-C and Laptop HDMI to Dell HDMI. – nize May 13 '22 at 17:48
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    Regarding "Edit 3", you won't be using the TB3 port as a TB3 port / in TB mode if you connect your USB-C monitor to it. There's a difference between USB-C monitor and TB3 monitor (like one from Apple or so), just like the case of docks. – Tom Yan May 13 '22 at 18:04
  • Ok, thanks for the clarification! This is SO complex. For some reason I'm led to believe that a certain physical form factor implies a certain function. That means that there still is a chance that it would work using a TB3 dock. For me the MST function of the Dell monitor makes no sense in case the computer connection anyway can't handle the summed throughput. – nize May 13 '22 at 18:11
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    Yeah, theoretically with a TB3 dock that has **two** DP ports (either in "DP DP" form or perhaps, USB-C form) you should get it working as you desire, unless either the TB3 port of your laptop or the dock is sort of "crippled". Be careful with TB3 dock with only **one** DP port though, unless that one port supports DP **1.4** (HBR**3**), like your Dell monitor (claims it) does for its USB-C port, it won't make the MST function on your monitor "better". Actually you might need a TB3 dock with two DP ports anyway because of the capability (DP **1.2**) of your laptop itself. – Tom Yan May 13 '22 at 18:33
  • From page 17 in https://stinriverstorageprod.blob.core.windows.net/images/DELL/210-BDDW/639030.pdf I gather that, even if I would use a laptop supporting DP 1.4 (HBR3), the max resolution of the second monitor connected using MST could max be a 2560x1440 @ 60 Hz. – nize May 14 '22 at 16:59
  • Well, that *might* be merely referring to the maximum/optimal resolution of the screen itself. In any case, I figure the TB3-to-2DP adapter I linked would be your *best bet*. – Tom Yan May 15 '22 at 14:31

2 Answers2

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The ideal setup would be to only need to connect a single USB-C output from my computer (handling both energy, monitors and the USB-stuff connected to the monitors). How would I do this?

A dock.

We use Lenovo USB-C Docks, which everything plugs into and then a singular USB-C connects to the computer. This chargers, provides ethernet and all USB-C and USB connected functions.

As for the poor quality on Huawei - have you tried connecting the computer to the Huawei first, and then DP to the Dell? Does that result in the Dell having poor image quality?

bce
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  • Yes, tried also the other way around: Computer USB-C to Huawei USB-C and then Huawei USB out to Dell monitor USB-C. It didn't give any image on the Dell monitor as far as I remember. – nize May 13 '22 at 15:50
  • I was hoping a dock would not be needed since I chose the monitors with many USB ports so that they themselves could work as docks, reducing the number of devices. But maybe the built-in docks of these monitors are not powerful enough? Also one reason for going with P2423DE was the 90W charging using USB. – nize May 13 '22 at 15:53
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You want to look for a USB-C dock.

I currently have one connected to my laptop. One USB cable from the dock to my laptop with 2 screens attached to it. The power is also provided through the USB-C dock via the single cable

Randomhero
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