What is USB4? – How USB4 Works | Synopsys
Table of Contents

Definition

A specification released in August 2019 by the USB Implementers Forum, USB4 is not a faster version of USB 3.x. Rather, USB4 tunnels USB 3.x, DisplayPort, PCIe®, and optional host-to-host traffic in one transport. USB4 docks and devices extract tunneled USB, PCIe, or DisplayPort traffic as needed.

Host-to-host tunneling enables 10Gbps network connection between two USB4 hosts. Tunneled PCIe enables “out-of-the-box” PCIe devices like NVMe storage, external graphic cards, AI accelerators, etc. to be easily connected to any USB4 host.

USB4 uses Type-C connector and cables, and allows power, data, video, and audio to co-exist, enabling a simple, one-cable docking station solution for laptops, etc. In addition, any legacy USB or DisplayPort product with a USB-C connector or the appropriate adapter cable will work with any USB4 port. 

Implementation options for USB4 | Synopsys

How Does USB4 Work?

USB4 has its own protocol and error correction,  and removes some of the legacy transport protocol overhead to increase available bandwidth. The USB4 host router manages bandwidth needs for the various tunneled traffic.

USB4 allows multiple tiers or layers for complex device trees. The USB4 device router routes tunneled traffic to the appropriate downstream ports and extracts tunneled traffic for its own use as needed. 

Based on Thunderbolt technology that has been successfully deployed for more than a decade, USB4 has now become mainstream for most mid- and high-end laptops and desktops. 


Benefits of USB4

USB4 enables single cable, single connection for power, data, video, and audio. Here are some key benefits of the specification:

  • It enables a simple, standardized docking station that works with any USB4 host 
  • There is no need for a ‘matching’ docking station and laptop, reducing cost and complexity for large IT departments
  • USB4 docking stations last for many years and can easily be re-purposed, which reduces e-waste
  • USB4-compatible docking stations have multiple price points depending on complexity; a USB4 laptop can connect to a low-cost USB/HDMI mini-dock at home, as well as to a more expensive and higher functionality USB4 docking station in the office

USB4 tunnels USB, DisplayPort, PCIe and optional host-to-host traffic.

  • Tunneled PCIe allows connectivity between NVMe storage, external graphics, AI accelerators, etc.; there is no need for bulky plug-in boards and PCIe slots in the USB4 host
  • Any legacy DisplayPort sink or monitor can be connected to a USB4 port; available, affordable DisplayPort-to-HDMI adapter cables allow any TV or HDMI monitor to connect to a USB4 port
  • Any legacy USB device can be connected to a USB4 port; This enables all existing USB devices to be used even if they are not USB4 compatible
  • Host-to-host traffic allows 10Gbps network connection between two hosts using standard USB-C cables; There is no need for advanced network cards, dongles, etc. or complex configuration and management to enable and maintain the connection

USB4 and Synopsys

Synopsys offers compliant USB4 PHY, USB4 host router, and USB4 device router IP along with USB4 Verification IP to ensure interoperability and successful adoption of the USB4 specification.  

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