USB Implementers Forum Announces the Publication of Its Thunderbolt 3-Based USB4 Standard

Offers up to 40Gb/s throughput, PCI Express, and DisplayPort connectivity — plus compatibility back to USB 2.0.

Gareth Halfacree
2 months agoHardware 101
USB4 will be compatible with existing USB Type-C cables (top). (📷: USB-IF)

The USB Implementers Forum (USB-IF), the cross-vendor organization in charge of the Universal Serial Bus (USB) standard, has announced the publication of USB4 — the next-generation interconnect based on Intel's Thunderbolt protocol.

Formally announced as USB4 — a shift from the naming convention used up to the current USB 3.2 standard — back in March last year, USB4 is built around Intel's Thunderbolt connectivity standard, which incorporates PCI Express and DisplayPort plus relatively high-wattage power delivery connectivity in a single cable. While Thunderbolt has previously stood in competition to USB, Intel donated the standard to the USB Promoter Group in order for it to form the underpinnings of USB4.

"Releasing the Thunderbolt protocol specification is a significant milestone for making today's simplest and most versatile port available to everyone," claimed Intel's Jason Ziller at the time. "By collaborating with the USB Promoter Group, we're opening the doors for innovation across a wide range of devices and increasing compatibility to deliver better experiences to consumers."

The shift to Thunderbolt doesn't mean a lack of backwards-compatibility, though: USB4 will, USB-IF has confirmed, be fully backwards compatible with previous USB devices from the current top-end USB 3.2 Gen 2x2 standard down to USB 2.0 - though not USB 1.0, the original variant which is rarely seen in modern hardware. Being based, as it is, on Thunderbolt 3 also means USB4 will work with existing Thunderbolt devices, the organization has confirmed.

As published, USB4 offers up to 20Gb/s throughput on a dual-lane connection using existing USB Type-C connectivity; an as-yet unreleased high-speed cable will increase this peak throughput to 40Gb/s. Both versions will be capable of carrying DisplayPort and PCI Express lanes, allowing for easy connectivity to external display devices and other hardware - and, in a shift from current standards, allows for multiple data and display protocols to be used simultaneously.

The specification is available to download now as part of the document library of USB.org.

Gareth Halfacree
Freelance journalist, technical author, hacker, tinkerer, erstwhile sysadmin. For hire: freelance@halfacree.co.uk.
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