Using the 23.7-inch LG UltraFine 4K Display over USB-C

Discussion in 'Mac Accessories' started by Aiwi, May 25, 2019.

  1. Aiwi macrumors newbie


    Oct 21, 2010
    The previous 21" 4K Ultrafine was connected to your computer using the USB standard. According to the following support document over at Apple, the new 24" monitor not only has Thunderbolt 3 but also USB as display input.

    Has anyone been able to confirm this? I am curious whether I can connect it to my RTX GPU using the GPU USB-C connector and a USB-C-USB-C cable. On the previous Ultrafine 4K 21" this is fully possible. Albeit not really useful in macOS just yet due to the lack of drivers.
  2. chrfr macrumors 604

    Jul 11, 2009
    Why would Apple put out a technical document detailing the connections and compatibility and then lie about it?
  3. changguangyu macrumors newbie


    Sep 15, 2017
    Yes. You can. USB c of RTX is VirtualLink standard, which is DP1.4 + USB 3.1 Gen2 + 27w power delivery.
  4. joevt macrumors 6502

    Jun 21, 2012
    VirtualLink is a new USB-C alt mode.

    The new LG display uses either DisplayPort alt mode (with USB 2.0) or Thunderbolt (which is basically another USB-C alt mode). Thankfully, the RTX cards also support DisplayPort alt mode. The new LG display is able to use USB-C or Thunderbolt because it uses the new Titan Ridge Thunderbolt 3 controller.

    DisplayPort alt mode has a couple different versions:
    - USB 3.1 gen 2 with two lanes of DisplayPort (allows 4K 30 Hz when using DisplayPort 1.2).
    - USB 2.0 with four lanes of DisplayPort. I believe this is the mode used by the new LG display (like the older LG display) otherwise it wouldn't be able to support 4K 60Hz with older Macs.

    VirtualLink is similar to the latter mode, but can transmit USB 3.1 gen 2 over the lines that are normally used for USB 2.0. This requires a new cable spec to beef up those lines.

    The support page says 4K 60 Hz is supported by the MacBook (Retina, 12-inch, Early 2016) but the technical specifications say that that MacBook only supports 4K 30 Hz. Maybe the 10.14.5 version of Mojave (that the support page says is required) unlocks that resolution for the MacBook?

    The support page does not mention computers that don't have Thunderbolt or USB-C ports. Does this mean the display can't work with a Moshi USB-C to DisplayPort Cable (it's supposed to be bi-directional)? If that's true, then these computers would require a DisplayPort to USB-C converter such as a Sunix UPD2018 or a Delock 89582 or a GC-ALPINE RIDGE or a GC-TITAN RIDGE.

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3 May 25, 2019