To USB or Not to USB


DisplayPort and USB Type-C (Part 1 of a series)

DisplayPort became a associated USB when USB Type-C was launched. The Type-C connector provides additional pin/signals/wires to run  simultaneous lanes of more data.  The additional lanes are called Alternate Mode or “Alt-Mode” for short.  It is possible to run both USB on the USB lines and and DisplayPort in Alt Mode.

The physical connector as shown below has both the Tx+/Tx- and Rx+/Rx- wires for the USB 3.1 traffic, and D+/D- for the USB 2.0 traffic. Only one group/set needs to be used for actual traffic.  The remaining ones will be use for Alt-Mode.


VESA announced a compliance program for using USB Type-C with DisplayPort back on December.


My hope is that the DisplayPort compliance test program is run with the formality and rigidity of the USB program. I’m simply not yet familiar with the compliance process. I’m learning..


What is DisplayPort?

DisplayPort is standard for moving video content from a source to a display (TV, PC Monitor, or projector).

  • It is like HDMI, except HDMI is completely standard in the consumer world.
    • HDMI is a closed, proprietary standard that requires royalties.
    • It is standard everywhere and will be around forever. (Until wireless gets it’s act together)
    • HDMI was/is standard on most consumer laptops and many business laptops
  • DisplayPort is royalty free.
  • It’s supported by the PC chipset makers.
  • It was most widely used in Apple computers in the minDisplayPort format (mDP).
  • Apple adopted Thunderbolt, a proprietary standard that included DP and PCIe. So the same physical port could support a normal mDP connection or a Thunderbolt connection. The advantage to the use is they could buy a new PC, connect it to an existing DP monitor (OR) buy a fance new DP and Thunderbolt monitor, and use it with an old PC supporting only mDP. Pretty cool
  • Business laptops over the past few years have had full-size DisplayPorts on business PCs. (More PCs have HDMI). Those will likely go away in the next few years to be replaced by USB Type C recepticles supporting both USB and Displayport.


Overview of DisplayPort Standards

The current DisplayPort standard shipping in volume is DisplayPort 1.3a. Some Business PCs and Gaming computers have it. It supports 4k, and maybe 5k monitors.  It uses a larger connector.

(Most PCs have a full HDMI connector).


The full size DP connector is used on laptops, monitors, and docking stations for Windows based PCs.


Mini DisplayPort (mDP) is the small form factor connector used on almost exclusively on Apple Laptops. (I don’t know why.)


Now, on both PCs and Apples It’s the USB Type-C connector.  For the Apple it usually uses a Thunderbolt 2 chip supporting multiplexed PCIe and DisplayPort and USB.

For PCs, its usually just USB 3.1 and sometimes DisplayPort if it’s using a Thunderbolt chip.

In the future, all DisplayPort will be USB Type-C connectors. Because everything will be Type-C.


USB Type-C supports both DisplayPort 1.3a and 1.4a. It’s actually transparent to the connector. The connector is designed to be scalable to higher speeds.

I’ve watched this video 20 times without sound.


Here’s the follow-up with the family who took the whole thing with a sense of humor.–252072

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