USB4: What You Need to Know About the Latest USB Technology

26-08-2020 | By Robin Mitchell

USB has been one of the best examples of a standardised system that has brought convenience and compatibility, featuring various connectors like Type A Connector, USB-C Connectors, and high-speed connector options. A new version, 4, is in the works, but what is USB4, how does it differ from previous versions of USB, and will it support earlier versions of USB?

What is USB?

USB stands for Universal Serial Bus, which is an acronym. As the name suggests, USB is a serial connection meaning that all data is transmitted bit by bit (whereas parallel busses transmit multiple bits simultaneously). USB was devised in 1995, and ever since has provided devices with a common standardised bus that has massively helped computing. While the first operating systems that supported USB required drivers, modern systems can often automatically identify devices (such as Windows 10), making USB an extremely convenient protocol.

USB is plug-and-play, meaning USB devices can be connected, disconnected, and connected again without needing to restart hardware or the operating system. An interesting fact about USB is that data is transmitted on a pair of wires called D+ and D-, which make up a differential signal and help USB operate at high speeds by removing common-mode noise in cables.

What is USB4?

USB4 is the latest iteration of USB that was announced in August 2019. While the standard was announced in 2019, it often takes time for the industry to react to the announcement and produce hardware. USB 3 has been around since 2008. USB 3 ports have become more prevalent in recent years (these can be identified with their blue colouring instead of the usual black, which represents USB 2), and this demonstrates how long it takes for modern hardware to adapt to new protocols. 

USB4 is aimed at providing significantly faster transfer speeds, better port usage, and the ability to provide tunnelling of display ports and PCIe to external devices. This allows USB4 devices to operate as PCIe devices, graphics display ports, and much more.

Features of USB4

USB-C connectors

The first major change of USB4 is the requirement for USB-C connectors. USB C connectors are very different from other USB connectors for several reasons. The first is that USB-C connectors can be inserted in any orientation and still work (whereas traditional USB Type-A ports suffer from the orientation problem).  USB4 also offers more connection options than previous versions of USB, and supports power delivery of up to 100W, which is made possible through the use of USB-C connectors.

The second is that USB-C connectors, utilising more connections, can provide greater power than their earlier counterparts (up to 3A per port). USB4 supports power delivery of up to 100W, making it capable of powering most laptops and other high-powered devices.

Faster transfer speeds

USB4 supports data rates of at least 20Gbps and up to 40Gbps, whereas USB 2 offers a maximum data transfer rate of 480Mbps. USB4 achieves these high data transfer rates through a new encoding scheme called Pulse Amplitude Modulation with 2 symbols (PAM-2), which allows for two bits of data to be transmitted per clock cycle, doubling the data transfer rate compared to previous versions of USB.

Better port usage

USB4, being compatible with Thunderbolt 3, supports all previous versions of USB, down to 2. USB4 is based on the Thunderbolt 3 protocol, which was developed by Intel. This means that USB4 supports all of the features of Thunderbolt 3, including the ability to transfer data, video, and power over a single cable. USB4 also supports multiple data and display protocols, including USB 3.2, Thunderbolt 3, DisplayPort 1.4, and PCIe, making it versatile and capable of supporting a wide range of applications, such as external storage, displays, and graphics cards.

USB4 vs. Previous Versions

Besides the use of the USB-C connector and increased speeds, USB4 is virtually identical in protocol and thus retains backward compatibility with older devices. However, devices that do not have a USB-C connector require an adaptor to work with new USB4 ports. Keep in mind that not all devices may fully utilise USB4's enhanced power delivery capabilities, and adapters might be necessary for some older devices to function with USB4.  

Additionally, while USB4 is backwards compatible with previous versions of USB, some older devices may not be able to take advantage of the faster transfer speeds offered by USB4. It is also worth considering the potential drawbacks and limitations of USB4, as not all devices may be able to fully utilise its capabilities. Despite this, the future of USB technology is promising, and there is room for continued innovation and improvement.

Key Differences Between USB4 and Previous Versions:

  1. USB4 requires the use of USB-C connectors, which offer more connection options and support power delivery of up to 100W.
  2. USB4 provides faster data transfer rates of up to 20Gbps (minimum) and 40Gbps (maximum) through a new encoding scheme called PAM-2.
  3. USB4 is based on the Thunderbolt 3 protocol and is compatible with all previous versions of USB (down to 2), as well as multiple data and display protocols.
  4. USB4's increased power delivery capabilities may not be fully utilised by all devices, and some older devices may require adapters to work with USB4.
  5. USB4 retains backward compatibility with older devices, but devices without USB-C connectors will require an adapter to work with USB4 ports.

What is Intel doing with the newest USB type?

With USB4 around the corner, there are concerns that manufacturers will begin to phase out older USB ports. According to a leak from a well-known leaker on Twitter (_rogame), an internal document at Intel shows multiple USB4 controllers that make no mention of other connectors besides USB-C. If so, this would suggest that the new controllers will not support older USB Type-A connectors; thus, any designs based on the said controller would have to omit USB Type-A connectors. The documentation also makes no mention of USB 2 or USB 1.1 support, which is widely used by hardware, including cameras, printers, scanners, and other office hardware.

While other companies such as Apple have not included USB Type-A ports in their laptops for several years now, the supposed move by Intel to scrap the USB Type-A port shows an industrial attempt to move away from them.

However, is this a bad thing? Backwards compatibility is vital for the longevity of hardware, but there has to be a point where old hardware is decommissioned. For example, the parallel port was a key connector in computers of the past, but as time progressed, the port became antiquated as most moved towards USB. 

Fast forward to today's world, the size of files and the speed of external hardware have increased so much that the type-A USB connector is now the modern parallel port.

Future USB Technology (What Does The Future Hold?)

Utilising USB-C connectors not only enables higher transfer speeds but also delivers increased power capacity. While Type-A connectors have been widely used, it is time to move on from older technology and start to introduce 40Gbps technology, where files transfer to a flash drive in seconds instead of hours, and additional displays can be added using an external port instead of getting a new motherboard to support a second graphics card.


In conclusion, USB4 represents a significant advancement in USB technology, offering improved transfer speeds, power delivery capabilities, and enhanced versatility with the use of USB-C connectors. This latest iteration of USB not only maintains backward compatibility but also paves the way for future innovations in computing and device connectivity. As the industry continues to adapt to and adopt USB4, consumers can expect to see the benefits of faster data transfers, more efficient power delivery, and streamlined connections across a wide range of devices and applications. While the transition to USB4 may necessitate the use of adapters for some older devices, the long-term benefits of embracing this new technology far outweigh the short-term inconveniences. As USB technology continues to evolve, it will remain a crucial component in shaping the future of computing and device connectivity.


By Robin Mitchell

Robin Mitchell is an electronic engineer who has been involved in electronics since the age of 13. After completing a BEng at the University of Warwick, Robin moved into the field of online content creation, developing articles, news pieces, and projects aimed at professionals and makers alike. Currently, Robin runs a small electronics business, MitchElectronics, which produces educational kits and resources.