USB-IF publishes official USB 4 . specifications

By admin On Sep 3, 2019

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The USB Implementers Forum has published the official USB 4 specifications. The new USB generation is based on the Thunderbolt specification and supports a bandwidth of up to 40Gbit/s with certified USB type-c cables.

Usb 4 was already announced earlier this year, but the official specifications are now concrete and released. The USB 4 architecture is based on Thunderbolt 3. This is possible because Intel has made the technology available royalty free. With a speed of 40Gbit/s, USB 4 doubles the maximum bandwidth compared to SuperSpeed 20Gbit/s, or the USB 3.2 2×2 specification. Incidentally, the specification refers to the 20Gbit/s processing with ‘usb4 gen 2×2’ and to the 40GBit/s processing with ‘usb4 gen 3×2’.

The available bandwidth can be used flexibly for multiple data and display protocols at the same time. According to the USB-IF, this is an important difference compared to USB 3.2. The organization describes usb4 as a tunneling architecture designed to combine multiple protocols on a single physical interface. The total speed and bandwidth of usb4 can therefore be dynamically distributed. In addition to USB 3.2 tunneling, tunneling based on displayport and PCI-e is possible.

A component that the USB-IF calls “router” is a fundamental building block of usb4. This component, not to be confused with a ‘usb4 hub’, routes the tunneled traffic and resides in every host, hub and device based on the next generation USB. Hosts and hubs must have displayport alt mode support; a hub must have a pci-e switch, with a host a pci-e controller is optional.

Thanks to the integration with Thunderbolt, USB-C cables certified for the Thunderbolt speed of 40Gbit/s can also be used with the new USB specification. USB 4 will also be backwards compatible with USB 3.2, USB 2.0 and Thunderbolt 3. The full specifications can be found on the USB-IF site. More information about the USB 4 specification will be announced at the USB Developer Days 2019 in Seattle. These will take place on 17 and 18 September.

It will probably take a few more years before USB 4 is incorporated into hardware. USB 3.2 will come first, for which the first controllers will be released this year and integration into hardware is expected next year. The USB 3.2 specification was already published in September 2017.