October 20th, 2022 at 11:21 am by Andreas Link – USB 4 2.0 is here and the new standard offers up to 80 Gbit/s synchronous or 120 Gbit/s asynchronous transfer performance. USB 4 2.0 covers Displayport and PCI-Express 4.0, is backward compatible and has the same connectors as USB 4 1.0.
The USB Implementers Forum has published details on the new expansion stage for USB 4. USB 4 2.0 is now official and now supports data rates of up to 80 Gbit/s. VESA, which works closely with the USB Implementers Forum on Displayport 2.1 and certifies cables accordingly, had already anticipated this. As with Displayport, USB 4 2.0 is mechanically fully compatible with USB 4 1.0 and also fundamentally backwards compatible. But that doesn’t make it clearer. Customers must primarily pay attention to which standard is supported by the device and buy cables that are certified accordingly.
In addition to passive cables, there will also be active cables with USB 4.0 in the future, which will be equipped with Type-C connectors. These are necessary to achieve the higher transfer performance, because they are only achieved with changes to the protocol and not via electrical changes such as more lanes. In order to realize the now higher transfer powers, a pulse amplitude modulation with three states (PAM-3; -1, 0, +1) is used. An asymmetric transmission mode will also be introduced, allowing 120 Gbit/s in one direction while the other direction is throttled to 40 Gbit/s.
USB 4 2.0 to USB 3.2 is downward compatible by means of a tunnel, which now delivers twice as much as before at 20 Gbit/s. In addition to VESA Displayport 2.1, PCI-SIG is also on board and supports USB 4 with PCI-Express 4.0. And in the background, Intel is also haunting Thunderbolt. USB is thus increasingly what the name promised when it was first introduced: a universal, serial bus. In recent years, this was partly at the expense of clarity, but today you can basically operate a large number of devices and protocols with a USB connection and cable.
USB 4 2.0 key features
Operates at up to 80Gbps using a new physical layer architecture that relies on PAM3 signal encoding over existing passive 40Gbps USB Type-C cables and redefined 80Gbps USB type -C active cable.
> Optionally, the USB Type-C signal interface can be used for specific applications, such as For example, driving very high-performance USB-4 based displays, can be configured asymmetrically to deliver up to 120Gbps in one direction while maintaining 40Gbps in the other direction.Updates to data and display protocols for better use of the higher bandwidth available
> USB data architecture updates now enable Enhanced SuperSpeed USB data tunneling in excess of 20Gbps.
> Conformity to Displayport Revision 2.1 and PCI-Express Revision 4. Backward compatibility with all previous USB versions.
The aim is to help the overview by requiring the partners to name their connections according to their speed. For example USB 20 Gbit/s. This makes it clear what transfer performance can be expected from this socket and what transfer performance is required for the cable. Which type of connector is present, nowadays increasingly USB Type-C, can be seen with the eye. Unfortunately, the specifications of the USB IF are not binding and devices will not always be properly labeled. But as soon as official logos are used, you will see the speed. However, it will probably take another 12 to 18 months before the first products based on the new standard appear.