Definition - DP Alt Mode

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:

  • USB 3.1 Gen 2 data transfer rates of 10Gbps
  • USB Power Delivery 2.0 – Up to 100W of bi-directional power delivery
  • DisplayPort Alternate Mode (DP Alt Mode) with DP 1.3 support


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

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