USB4: What are the Advantages of USB 4.0?

What are the Advantages of USB4

What is USB4?

USB4, also known as USB 4.0, was introduced by the USB Implementers Forum (USB-IF) on August 29, 2019. It is based on the Thunderbolt 3 protocol contributed by Intel. USB4 uses a Type-C connector exclusively and requires USB Power Delivery (PD). With a minimum speed of 20 Gbit/s and a maximum of 40 Gbit/s, USB4 can achieve higher effective data rates through dynamic tunnelling of data types.

In comparison to earlier USB standards, USB4 supports tunnelling of DisplayPort and PCI Express and ensures compatibility with Thunderbolt 3 devices. Thunderbolt 4 devices are mandated to support USB4.

The USB4 2.0 specification was released on October 18, 2022 by the USB Implementers Forum.

USB4 40Gbps

USB4 doubles the bandwidth to extend USB-C performance

What are the Main Advantages of USB 4.0?

The new USB 4 standard has three main benefits over prior versions of USB.

  • 40 Gbps Maximum Speed: By using two-lane cables, devices are able to operate at up to 40 Gbps, the same speed as Thunderbolt 3. The data is transmitted in two sets of four bidirectional lanes.
  • DisplayPort Alt Mode 2.0: USB 4 supports DisplayPort 2.0 over its alternative mode. DisplayPort 2.0 can support 8K resolution at 60 Hz with HDR10 colour.
    • DisplayPort 2.0 can use up to 80 Gbps, which is double the amount available to USB data, because it sends all the data in one direction (to the monitor) and can thus use all eight data lanes at once.
  • Better Resource Allocation for Video, PCIe: In lieu of alternative mode where the other interface takes over the connection, USB4 devices can use a process called “protocol tunnelling” that sends DisplayPort, PCIe and USB packets at the same time while allocating bandwidth accordingly.
    • So, if the video only needs 20 percent of the bandwidth to drive your 1080p monitor that’s also a hub, the other 80 percent will be free for transferring files from your external SSD which can operate over either USB protocol or PCIe.

USB4 Will Use Type-C Ports?

USB 4 exclusively functions via the Type-C connector and won’t support older Type-A ports. This aligns with other modern standards like USB Power Delivery that also require Type-C. Using an adapter to connect to a Type-A USB 3 port limited to 5 Gbps will reduce performance to the lowest supported levels of speed and power.

USB4 Data Transfer Modes

USB4 doesn’t offer its own data transfer mechanisms unlike USB 3.x, instead primarily tunneling existing protocols such as USB 3.2 and DisplayPort, with optional PCIe support. It includes a native Host-to-Host protocol used for IP Networking between two hosts. When PCIe tunnelling isn’t supported, maximum non-display bandwidth drops to USB 3.2’s limit of 20 Gbit/s; a 10 Gbit/s rate is the mandatory minimum.

USB4 specifies tunnelling of:

  • USB 3.2 (“Enhanced Super speed”) Tunnelling
  • DisplayPort 1.4a-based Tunnelling
  • PCI Express (PCIe)-based Tunnelling
  • USB4 also supports DisplayPort Alternate Mode. This means DP can be sent via USB4 tunnelling or DP Alternate Mode.
  • DisplayPort Alt Mode 2.0: USB 4 supports DisplayPort 2.0 over its alternative mode. DisplayPort 2.0 can support 8K resolution at 60 Hz with HDR10 colour and can use up to 80 Gbit/s which is same amount available to USB data, but just unidirectional.
  • Legacy USB (1–2) is always supported using the dedicated wires in the USB-C connector.

Data transfer modes

Some transfer modes are supported by all USB4 devices, support for others is optional. The requirements for supported modes depend on the type of device.

ModeHostHubPeripheral device
Legacy USB (1–2) (max. 480 Mbit/s)YesYesYes
USB4 20 Gbit/s TransportYesYesOptional
USB4 40 Gbit/s TransportOptionalYesOptional
Tunnelled USB 3.2 (10 Gbit/s)YesYesYes
Tunnelled USB 3.2 (20 Gbit/s)OptionalOptionalOptional
Tunnelled DisplayPortYesYesOptional
Tunnelled PCI ExpressOptionalYesOptional
Host-to-Host communicationsYesYes
DisplayPort Alternate ModeYesYesOptional
Thunderbolt Alternate ModeOptionalYesOptional
USB-C Alternate ModesOptionalOptionalOptional
USB4 Ports
  • USB4 Power Delivery: USB4 mandates USB Power Delivery (USB PD), initiating connections only after negotiating a PD contract, with sources providing a minimum of 7.5 W (5 V, 1.5 A) per port. Sinks initially demand less than 250 mA before negotiation, but with USB PD, power can extend up to 240 W. The ‘Standard Power range’ offers up to 100 W.
  • Thunderbolt 3 Compatibility: USB4 aims to maintain compatibility with USB and Thunderbolt devices, mandating Thunderbolt 3 compatibility for hubs, but not for all devices. This includes implementing 40 Gbit/s data transfer and supplying at least 15 W.
  • USB4 Hardware Support: Announced during CES 2020, USB-IF and Intel promoted USB4 alignment with Thunderbolt 4 standards. The first USB4 compatible devices were Intel’s 11th generation Tiger Lake processors, followed by Apple’s 2020 M1 devices including MacBook Air, MacBook Pro (13-inch), and Mac mini.
  • USB4 Software Support
    • Windows 11, released on 5 October 2021
    • Linux kernel 5.6, released on 29 March 2020
    • macOS Big Sur (11.0), released on 12 November 2020

Products with USB4 Support

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