USB4

USB4 is a hardware interface specification developed and released by the USB Implementers Forum. It represents a significant architectural advancement over previous standards, fundamentally integrating the Thunderbolt 3 protocol specification. The standard mandates the use of the USB-C connector and supports multiple data and display protocols simultaneously over a single connection.

Overview

The development of this specification was announced by the USB Implementers Forum in 2019, with the formal release of the specification occurring later that year. It is architecturally based on the Thunderbolt 3 protocol, a technology originally developed by Intel Corporation. A primary goal was to create a unified, high-performance connectivity standard that simplifies the user experience across a wide range of devices, from Microsoft Surface laptops to Apple Inc.'s MacBook line. The specification is managed and certified by the USB Implementers Forum, ensuring compliance and interoperability among products from various manufacturers like Dell Technologies, HP Inc., and Lenovo.

Technical specifications

The architecture utilizes a dual-lane operation built upon the existing USB-C connector and USB Power Delivery specifications. It supports a maximum aggregate bandwidth of 40 Gbit/s, achieved through the use of two-lane USB-C cables operating at 20 Gbit/s per lane. The specification natively supports tunneling of multiple protocols, including PCI Express for high-speed data and DisplayPort for video, allowing them to share the bandwidth dynamically. This tunneling capability is a direct inheritance from the Thunderbolt 3 standard. Mandatory support for USB Power Delivery enables power delivery up to 240 watts for charging compatible devices. The data encoding scheme is based on PCI Express and uses a packet-based routing system managed by a central router within the host.

Compatibility and interoperability

A key design principle is backward compatibility with several major prior standards. It maintains full compatibility with USB 3.2, USB 2.0, and Thunderbolt 3. All certified hosts, devices, and cables must support the USB-C connector. For a product to be certified, it must support a minimum of 20 Gbit/s operation, with 40 Gbit/s being an optional, higher-performance tier. The USB Implementers Forum requires rigorous testing for certification, which includes validation of DisplayPort and PCI Express tunneling. This ensures that peripherals from companies like Western Digital for storage or NVIDIA for external graphics will function correctly. The standard also defines specific logos for certified products to aid consumer identification.

Version history and development

The initial version 1.0 specification was published in 2019 by the USB Implementers Forum. This release formally incorporated the Thunderbolt 3 protocol specification, which Intel Corporation had contributed to the USB Implementers Forum royalty-free. A subsequent update, USB4 Version 2.0, was announced in 2022, promising doubled data rates and enhanced data tunneling performance. The development of these specifications is a collaborative effort involving many prominent technology companies within the USB Implementers Forum, including Microsoft, Apple Inc., Intel Corporation, and HP Inc.. The evolution of the standard is closely tied to advancements in PCI Express and DisplayPort technologies.

Applications and use cases

The high bandwidth and protocol flexibility enable a wide array of advanced applications. It is extensively used for connecting high-performance external storage devices, such as NVMe solid-state drives in enclosures from manufacturers like Samsung Electronics. The DisplayPort tunneling feature allows it to drive multiple high-resolution monitors, a common requirement for workstations from Dell Technologies or creative professionals using Apple Inc. hardware. The PCI Express tunneling is crucial for external graphics enclosures, enabling laptops to leverage powerful desktop GPUs from AMD or NVIDIA. Furthermore, its integration into docking stations from brands like CalDigit or OWC allows a single cable to provide power, network connectivity via Ethernet, peripheral connections, and video output to monitors from LG Electronics or Samsung Electronics.

Category:Computer hardware Category:Computer buses Category:USB