Add USB-C with DP ALT-mode to your Desktop PC

[Updated April 2021 with latest Thunderbolt 4 add-in boards]

Recently I’ve received several requests from customers who want to share a Docking station with monitor/mouse/keyboard between a Desktop PC and a modern Laptop without using a software solution like Mouse without borders

Many modern laptops feature USB-C or Thunderbolt-3 which makes Docking connectivity simple with a single connector providing power, data, and monitors. But most Desktop PCs lack these ports. A variety of inexpensive PCI express -> USB-C add-in-boards available, but most are not compatible with monitors connected to Docks because they lack DisplayPort Alt mode support. So collected below are a set of solutions to upgrade your Desktop PC to have either a USB-C with DisplayPort alternate-mode OR a Thunderbolt 3 output.

USB-C+DP-ALT-mode PCIe add-in-boards

  • Sunix upd2018
  • Delock 89582 (re-brand of Sunix for EU market)
  • Dell re-brands of the Sunix board – check ebay! Different worldwide regions have different part numbers, but they are all the same board.
    • Dell YF1YR ($140 USD order direct from Dell)
    • Dell 1H0Y3 ($65 list for Enterprise bulk ordering – SFF bracket only)
    • Dell M0W58 ($65 list for Enterprise bulk ordering – Full-size bracket)
    • Dell WYY76 ($65 list for Enterprise bulk ordering – Half height bracket)

Notes:

  • The board only supports a single DisplayPort signal – so only works with 1 monitor.
  • To connect yoru GPU output to the board’s input, you’ll need a 1 foot DisplayPort -> DisplayPort cable.
  • If you don’t have a spare PCIe slot but you have a spare M.2 NVME slot (not SATA) you can use a M.2 nVME -> PCIe x4 adapter cable
  • Depending on the mainboard PCI slot topology, you may need to place the add-in card in the first slot that is typically used for a GPU. You may also need to change UEFI/BIOS settings to enable PCI lane bifurcation mode (x8/x8). This will ensure that both boards are connecting directly to the CPU rather than via the mainboard chipset. This arrangement may limit GPU throughput and on-board M.2 connector functionality.

Thunderbolt PCIe add-in-boards

Notes:

  • There are several older Alpine-Ridge based boards by Asus, GigaByte, ASRock, etc. but with dubious compatibility across USB-C accessories and mainboard brands.
  • Depending on the mainboard PCI slot topology, you may need to place the add-in card in the first slot that is typically used for a GPU. You may also need to change UEFI/BIOS settings to enable PCI lane bifurcation mode (x8/x8). This will ensure that both boards are connecting directly to the CPU rather than via the mainboard chipset. This arrangement may limit GPU throughput and on-board M.2 connector functionality.
  • If you don’t have a spare PCIe slot but you have a spare M.2 NVME slot (not SATA) you can use an M.2 nVME -> PCIe x4 adapter cable

GPU add-in-boards

External DP+USB -> USB-C multiplexers

Integrated mainboard graphics

Most mainboards using integrated graphics from Intel or AMD don’t have DisplayPort and only include HDMI. In order to use these with any of the aforementioned solutions, you need to convert the HDMI signal to DisplayPort using a reverse HDMI -> DP adapter.

References: 

Special thanks to /u/chx_ for research on the Sunix board and inspiring the article.

14 thoughts on “Add USB-C with DP ALT-mode to your Desktop PC

  1. There now are a few hdmi to USB-C DP-alt mode adapters based on the Lontium LT6711A. For example from UGreen and Delock.

    https://m.nl.aliexpress.com/item/1005001459544376.html
    https://www.delock.com/produkte/N_63251/merkmale.html

    The UGreen can also combine USB 2.0 with up to 4K@60Hz over 4 lanes DP1.2 speeds.
    I have that adapter en seems to work fine with my Raspberry pi 4.

    The chip also supports combining 2 lanes for USB 3 and 2 lanes for DP-alt mode, so that might also become available on other products.

    Like

    • The Delock looks great, but.. only 5V usb? it usually means 1.5A, so 7.5W, nowhere near the 60W common for usb-c power delivery.. I’m perplexed! Am I missing something?

      Like

      • Yes it is surprising that all these are not offering 5V@3A since pulling 15W from the PCI express slot is no big deal (bucking 12V down to 5V is simple enough).

        Pulling 60W from the 12V line and boost converting it to 15V is a bigger deal and rather expensive so that’s why you don’t see it on these boards. Plus implementing multi-voltage PD is a lot more complex than single voltage.

        Like

  2. Hey @danchar thanks for replying! I was talking about the adapters that Bernard linked, though.. those are not cards! And yet, they boast USB PD specs.. I googled a bit and the USB PD specs seems to mandate a wattage that neither the pci-e cards, much less the adapters, could ever sustain. So how the hell are these suppposed to work with anything requiring more than 5V??

    Like

    • Ok I understand the confusion. PD is 100% optional as part of the USB-C spec. And even if a vendor does claim PD support, all they really need to do is 5V @ 1A. In the case of these adapters, the HDMI and DIsplayPort only provide 5V or 3.3v @ 300mA or thereabouts So the power is coming from an separate micro-usb port which is limited to 5V @ 1A or thereabouts. So these adapters are really not well suited to VR goggles or USB-C portable monitors that consume more than 5W

      Like

  3. Ooooh I see! So they’re for the unfortunate soul who let’s say bought a desktop monitor that only has usb-c as its video input.. I was so hoping for the miracle adapter! I mean in theory the Lontium LT6711A does support PD so it would be a matter of having a usb-in that accepted some real power xD I guess we’ll have to wait

    Like

    • The usecase for the lontium chip is to connect a monitor through either DisplayPort or usb-c to a HDMI output device at 4K@60Hz. A good example device would be a Raspberry Pi 4, that only has a HDMI output (Usb-c to DisplayPort adapters are very simple and cheap and work when chained with the UGreen adapter with the Lontium chip).
      There also is a USB-C to Dual-Link DVI adapter sold with Club3d, StarTech and other branding that works when chained to the UGreen. Allowing users to connect a Dual-Link DVI monitor to the Raspberry Pi 4 through HDMI at the native 2560×1600@60Hz.

      Like

  4. Hi Dan, thanks for the article. I have a scenario for this. Currently I have 2 Thunderbolt 3 laptops and a NUC, and my keyboard and mouse are plugged into a 4K USB-C monitor. This is really nice because I can switch what computer I’m using just by unplugging the USB-C cable and plugging it into the Thunderbolt 3 port on the computer I want. But the NUC is not a super powerful computer. Whatever I get or build to replace the NUC, I want to keep this convenience. I think I understand this article but I want to be sure: using the Sunix upd2018, I can build a PC or buy one and add that card, then it will “play nice” with that monitor and the stuff plugged into it? Does it matter if the DisplayPort signal going into the card comes from integrated or discrete graphics? Does this consume a lot of power (could be a problem if I buy a prebuilt that doesn’t have a lot of juice from some non-upgradeable power supply)? If it all looks good for my case, that’s awesome! It seems a lot easier, cheaper, and more flexible than finding a Thunderbolt 3 card and a compatible motherboard. And it seems like I can also add the card to a pre-built as long as it has the space for the card.

    Like

    • Hi – you have it exactly right. Integrated vs discrete GPU doesn’t matter as long as it is DisplayPort. If integrated only has HDMI, you may be able to use a bi-directional HDMI->DP cable (see my separate article on this), but there are potential compatibility issues with this approach and you may need to plug/un-plug a few times after reboots to get it to sync.

      The Sunix card itself consumes negligible power – unless the downstream USB-C device (like a portable monitor) consumes power over the wire. In that case, the card will draw up-to 15-20 watts. No need for a beefy power supply here. Some of the TB3 / TB4 cards will draw up to 35W when 2 TB3 power-consuming devices are plugged in – still not a big deal. If you’re plugging into a powered USB-C hub, or hub built-into a monitor, you’ll have no issues regarding power.

      Like

  5. This is very useful im going to try the newer wacom display link adapter since the old one is discontinued.

    I need something that has its own power because i am trying to use the nreal light ar headset on my pc.

    I just wanted to say thanks for this post. It was extremely dificult finding devices that supported video from hdmi or displayport out over usb-c.

    Then add the fact that the nreal uses only usbc for audio video and camera with a usbc male plug for input… It’s like the devs were afraid of someone using it on anything other than a phone.

    Liked by 1 person

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