USB 4.0 - The Next Generation of USB

26-08-2020 |   |  By Robin Mitchell

USB has been one of the best examples of a standardised system that has brought convenience and compatibility. A new version, 4.0, is in the works, but what is USB 4.0, how does it differ from previous versions of USB, and will it support previous versions of USB?

What is USB?

USB is an acronym and stands for Universal Serial Bus. As the name suggests, USB is a serial connection meaning that all data is transmitted bit by bit (whereas parallel busses transmit multiple bits at the same time). 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 that USB devices can be connected, disconnected, and connected again without needing to restart hardware or the operating system.

An interesting fact about USB, data is transmitted on a pair of wires, called D+ and D-. These make up a differential signal and helps USB to operate at high speeds by removing common-mode noise in cables. 

What is USB 4.0?

USB 4.0 is the latest iteration of USB that was announced in August of 2019. While the standard is now a year old, it often takes time for the industry to react to the announcement, and to produce hardware for. While USB 3.0 has been around since 2008, USB 3.0 ports are not common (these can be identified with their blue colouring instead of the usual black which represents USB 2.0), and this demonstrates how long it takes for modern hardware to adapt to new protocols. USB 4.0 is aimed at providing significantly faster transfer speeds, better port usage, and ability to provide tunnelling of display ports and PCIe to external devices. This allows USB 4.0 devices to operate as PCIe devices, graphics display ports, and much more.

How does USB 4.0 compare to previous USB versions?

The first major change of USB 4.0 is the requirement of 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 superposition). The second is that USB-C connectors, utilising more connections, can provide greater power than their earlier counterparts (up to 3A per port). USB 4.0 increases data rates up to a minimum of 20Gbps (40Gbps is also supported), while USB 2.0 supports up to 480Mbits. USB 4.0, which is compatible with Thunderbolt 3, supports all previous version of USB (down to 2.0). Besides the use of the USB-C connector and increased speeds, USB 4.0 is virtually identical in protocol and thus retaining backwards compatibility with older devices. However, devices that do not have a USB-C connector require an adaptor to work with new USB 4.0 ports.


What is Intel doing with USB 4.0?

With USB 4.0 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 USB 4.0 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, and thus any designs based off said controller would have to omit USB Type-A connectors. The documentation also makes no mention of USB 2.0 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 into 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. The use of USB-C not only allows for greater transfer speeds but provides more power. Type-A connectors will always hold a place in my heart, but its time to move on from old 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.

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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.

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