DisplayPort · 2014
DisplayPort over USB-C (Alt Mode)
How most USB-C ports send video. The USB-C pairs are handed over to DisplayPort.
- data: USB 2.0 or USB 3 alongside
- video: DP 1.4 (or 2.1) over USB-C
- power: USB PD at the same time
Spec card
- How
- the USB-C high-speed pairs switch to carrying DisplayPort lanes
- 4-lane mode
- all 4 pairs carry video; USB 2.0 data only
- 2-lane mode
- 2 pairs video, 2 pairs USB 3 data
- Versions
- DP 1.2, 1.4 or 2.1, depending on the device
- Logo
- a DisplayPort 'D' icon next to the port (not always present)
- Cable
- full-featured USB-C (USB 3 / 10Gbps or better)
Also sold as DP Alt ModeDisplayPort Alt ModeUSB-C videoDP over USB-C
The cable you need
A full-featured USB-C cable (10Gbps, 20Gbps, 40Gbps or Thunderbolt). Not a USB 2.0 "charging" cable.
Watch out for
- Not every USB-C port outputs video.
- Docks with USB 3 ports often leave only 2 lanes for video, so 4K 60 Hz is the ceiling without DSC.
- USB 2.0-only USB-C cables cannot carry Alt Mode video.
A USB-C cable has four high-speed wire pairs, and Alt Mode lets the two devices agree to use some of them for something other than USB. For DisplayPort, the port can hand over all four pairs, giving full DisplayPort bandwidth with only USB 2.0 data alongside, or two pairs, giving half the video bandwidth and keeping USB 3 data on the other two.
That split explains a lot. A USB-C monitor with a USB hub, or a cheap dock with USB 3 ports, often runs 2-lane mode: with DisplayPort 1.4 that's 12.96 Gbps, enough for 4K at 60 Hz, but not 4K 120. A direct USB-C to DisplayPort cable usually uses all four lanes.
Alt Mode is optional. Many phones and cheap laptops have USB-C ports with no video at all. Look for a DisplayPort or Thunderbolt icon by the port, or check the spec sheet for "DisplayPort Alt Mode".
What it can carry
Computed from each link's usable bandwidth; 4K at 60 Hz and above assumes 10-bit HDR colour. How.
| Mode | USB-C DP 1.4 ×2 | USB-C DP 1.4 ×4 |
|---|---|---|
| 1080p 60 Hz 8-bit | Fits 3.2 Gbps | Fits 3.2 Gbps |
| 1080p 144 Hz 8-bit | Fits 8.0 Gbps | Fits 8.0 Gbps |
| 1440p 144 Hz 8-bit | With DSC 14.1 Gbps | Fits 14.1 Gbps |
| 4K 30 Hz 8-bit | Fits 6.2 Gbps | Fits 6.2 Gbps |
| 4K 60 Hz 10-bit | With DSC 15.7 Gbps | Fits 15.7 Gbps |
| 4K 120 Hz 10-bit | With DSC 32.3 Gbps | With DSC 32.3 Gbps |
| 4K 144 Hz 10-bit | Too much 39.2 Gbps | With DSC 39.2 Gbps |
| 4K 240 Hz 10-bit | Too much 68.6 Gbps | With DSC 68.6 Gbps |
| 8K 60 Hz 10-bit | Too much 62.1 Gbps | With DSC 62.1 Gbps |