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DisplayPort Alt Mode 2.0 will work with USB 4

By Ng Chong Seng - on 4 May 2020, 12:50pm

DisplayPort Alt Mode 2.0 will work with USB 4

(Image: VESA.)

As USB 3.2 and USB-C continue to confuse consumers, the USB-IF is already moving ahead with USB 4. While we know that the spec includes the Thunderbolt 3 spec and works at 40Gbps, there are still many things not set in stone, such as interoperability with other protocols and devices.

One answer we’ve just gotten is from VESA (that’s the Video Electronics Standards Association), which has announced an updated DisplayPort Alternate Mode 2.0 spec that works with new USB-C devices, including the upcoming USB 4 standard. In short, with DP Alt Mode 2.0, USB 4 with its USB-C connector can now transmit up to 80Gbps of DisplayPort video data.

But how is that possible given that USB 4 supports 40Gbps? The answer is pretty simple: USB 4’s 40Gbps bandwidth is bi-directional. Since video is typically one way, DisplayPort Alt Mode 2.0 will use all four high-speed lanes in the cable to transmit 80Gbps (77.37Gbps effective).

(Image: VESA.)

Long story short, what we already know about DisplayPort 2 doesn’t change: it supports 8K (7,680 x 4,320) displays at 60Hz with full-color 30 bpp 4:4:4 HDR resolution uncompressed and 16K (15,360 x 8,460) displays at 60Hz with 30 bpp 4:4:4 HDR resolution with compression. The news is that with DisplayPort Alt Mode 2.0, these capabilities will work over a USB 4/USB-C connection.

According to AnandTech, DisplayPort Alt Mode 2.0 should work with most USB 4-compliant cables. With this mode, displays only need DisplayPort hardware to receive the video data and can skip the USB 4 controller.

VESA expects the first products using DisplayPort Alt Mode 2.0 to arrive in 2021.

Source: VESA, AnandTech.