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Tech Talk: Using USB-C and DisplayPort over Alt Mode

Continuing our discussion on display technologies, let’s turn our attention to USB-C and DisplayPort. The DisplayPort protocol, which used to have a unique connector, is now transferred by way of the USB-C connector. The Type-C connector delivers DisplayPort technology via an Alternative Mode (Alt Mode).

With USB-C you get:

Even though USB-C is capable of supporting all of these features, not all of them are present all the time. Users will need to know the specifications of their devices to understand the display protocols supported.

What is Alt Mode?

Alt Mode is a term you will come across frequently when investigating USB-C.

Alt Mode is a functional extension of USB-C which enables the USB connection to carry non-USB signals. Alt Mode(s) are optional capabilities that are unique to the USB-C connector or port that allow technologies, like DisplayPort and Thunderbolt 3, to be transmitted. Knowing what devices and ports support the various Alt Modes may be confusing and, at times, frustrating.

DisplayPort over Alt Mode

DisplayPort Alt Mode (DP Alt Mode) allows a USB-C equipped computer to connect directly to a display or monitor. The monitor will need to have a USB-C port for you to make this connection. You can still use a USB-C equipped laptop with monitors that have more traditional video ports, such as VGA, DVI, HDMI, and DisplayPort but you will need to get a USB-C video adapter.

What do I need to know before using DisplayPort over Alt Mode?

  • Confirm your computer’s USB-C port supports DP Alt Mode
  • Read the tech specs on the USB-C video adapter to ensure it supports the resolutions and refresh rates you want
  • If you are interested in a USB-C MST video adapter or laptop docking station, make sure your video card also supports MST

Our next and final display technology post will offer tips for using Thunderbolt 3 and MST.

Catch up on Display Technology 101 and tips and tricks for using MST and DisplayPort.

Stay tuned!

4 Comments

  1. Horst Wischnat 5 months ago

    How to check •whether my computer’s USB-C port supports DP Alt Mode

    • Susan Mutterback
      Susan Mutterback 5 months ago

      Hi Horst,
      Thanks for reading this post! The best place to find this information is your laptop’s manual or website.

  2. anilroy 2 months ago

    thanks for information of usb-c it is quite interesting for me to learn the new technology and their generations

  3. Paulus 4 weeks ago

    Thanks for this, it is nice to know someone else understands this. Indeed it is frustrating dealing with parts suppliers to confim the adaptors actually work!

    I have a Zenfone 3 deluxe that supposed to support USB-C Alt Mode, but I am having a terrible time getting a port replicator. I ended up just buying a Miracast dongle instead, and casting the phone to the monitor, then using usb-c for charging, keyboard and mouse, but still I want a docking station.

    Hopefully more adaptors and port replicators will come out, and the people selling them will actually know if they work or not!

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