Hi folks,

TL;DR, I’m trying to wrap my head around how MST-enabled docks work. To my knowledge, they’re fully fledged computers, so it would make sense it’s using a completely different protocol than the DisplayPort tunneled through USB-4 (which AMD has gimped to 1 instead of 2). which would mean that the FW13-Ryzen should be able to utilize the numbers of displays an MST-enabled dock offers.

I keep trying to find information on this. I find the wiki-stickied post on the framework forum is not really helping since they bungle both Intel and AMD framework toghether in the support matrix…

Anyway,

Here’s what I figured out so far. Everything below is only about the two upper USB4-ports, since the limitations of the other ports are well documented.

  • No MST controller on dock?
    • Needs display port through USB4.
    • AMD gimped the usb4 controller and only supports ONE attached display per USB-C ports
    • On Intel-based laptop, it would be supporting two displays on non-MST docks, since Intel TB4 has two display channels in a single connection.
  • MST Controller on dock?
    • With intel, does it multiplex each of the two channels or it’s a different beast?
    • Macbooks don’t support MST, stuck with SST, so with certain docks that supports MST, that cuts the numbers of external displays down to half + 1 mirrored.
    • WHAT ABOUT FRAMEWORK??? Is it like a MBP? Is MST a completely different beast?

When you have a TB4 dock that supports 4 displays WITH MST, like these insanely expensive Satechi ones, does it matter if it’s AMD or not?

What I’m trying to wrap my head around is, does MST needs the two DisplayPort channels to output on 4 different monitors, or it’s negotiating a completely different protocol to tunnel the pixels to the attached displays?

I currently got a triple screen configuration. I love it. However, it’s going through an external GPU and I’d like to get rid of it. It’s an ‘old’ vega64 that I could repurpose for other things, would make my desk cleaner, etc. OTOH, I love the idea of having just one cable plugged in to my laptop.

So, would a dock with MST, that says is supporting TB4 and 4 displays, works with more than two displays on the Framework Ryzen 13?

  • locomoka@alien.topBEnglish
    1·
    1 year ago

    I tried so hard understanding and following the usb-c situations and I am always kept surprised. Take for example my current setup, I have a thinkpad e16 amd that only had usb-c 3.2 gen 2. In theory, this laptop connected to my WD19TB should not be able to output more than 4k 60hz. However, I am able to drive more than that by having a second QHD screen.

    I dont know if you already own the laptop or not, but your best bet is to try the setup out by taking advantage of return policies.

    Tell me what are you screen monitor resolutions? Do you already have the laptop with an e-GPU? Are you just looking to buy the dock? I might suggest you get a second hand wd19tb. I bought mine for 80$ and has been working on every laptop I connect to for the last 3 years.

    • deranged_furby@alien.topOPBEnglish
      1·
      1 year ago

      I might keep my egpu tbh. I’m just bummed my GPU got dropped from AMDVLK, but it seems it’s still supported by RADV.

      As for the setup, 1x 4k @60, 2x 1080p@60.

      • locomoka@alien.topBEnglish
        1·
        1 year ago

        you will be fine connecting a wd19tb to a usb4 with those screens. I think the dock can supply 2x4k @ 60hz. wt19tb can be bought very cheaply and they are quiet while supplying 90W of power to the laptop.

        • rayddit519@alien.topBEnglish
          1·
          1 year ago

          3x 4K60 directly would be easily possible. In terms of bandwidth 4x 4K60 would be possible. 2x 4K60 + 1x4K100 would even be possible directly attached to a WD19TB (or any other dock based around a VMM53xx MST-Hub with access to a full 4xHBR3 DP connection and up-to-date firmware.

            • rayddit519@alien.topBEnglish
              1·
              1 year ago

              It launched before DSC was popular or available from most hosts. But the MST-hub is very much capable of DSC and with current firmware it has no problems with that.

              In fact the WD22TB4, which officially does support DSC is using the exact same chip on exact same firmware (the big part of the dock is identical across all WD19 and WD22 docks apart from the missing audio ports). You can even upgrade the WD19TB to WD22TB4 by simply replacing only the TB controller, the MST-Hub remains the same.

              ​

              Edit: have I mentioned I own 2 WD19TB?

              • locomoka@alien.topBEnglish
                1·
                1 year ago

                Ohhhh now I undetermined how come I can have two 4k 60hz on a usb-c 3.2gen2 laptop connected to my wd19tb. I never heard of DSC before. Thanks for sharing

    • rayddit519@alien.topBEnglish
      1·
      1 year ago

      We did not go over DSC. If the GPU supports DSC, each stream for a specific monitor inside an MST-connection could be individually compressed. And MST-Hubs, like the 3-Port VMM53xx hub inside your dock can uncompress that to a DP SST connection on every output.

      This allows you to achieve a total bandwidth across all displays on the MST-Hub of roughly 250% of the raw bandwidth of the available DP connection to the host. Which for example means you can typically get to 2x4K60 + 1x 4K30 on a 2xHBR3 DP Alt mode connection (i.e. half a modern DP connection).