The USB Implementers Forum (USB-IF), the industry consortium behind the development of the Universal Serial Bus (USB) specification, announced this week it has finalized the technical specifications for USB4, the next generation of the spec.
One of the most important aspects of USB4 (they have dispensed with the space between the acronym and the version number with this release) is that it merges USB with Thunderbolt 3, an Intel-designed interface that hasn’t really caught on outside of laptops despite its potential. For that reason, Intel gave the Thunderbolt spec to the USB consortium.
Unfortunately, Thunderbolt 3 is listed as an option for USB4 devices, so some will have it and some won’t. This will undoubtedly cause headaches, and hopefully all device makers will include Thunderbolt 3.
USB4 will use the same form factor as USB type-C, the small plug used in all modern Android phones and by Thunderbolt 3. It will be backwards compatible with USB 3.2, USB 2.0, as well as Thunderbolt. So, just about any existing USB type-C device can connect to a machine featuring a USB4 bus but will run at the connecting cable’s rated speed.
USB4: Less bulk, more speed
Because it supports Thunderbolt 3, the new connection will support both data and display protocols, so this could mean the small USB-C port replacing the big, bulky DVI port on monitors, and monitors coming with multiple USB4 ports to act as a hub.
Which gets to the main point of the new standard: It offers dual-lane 40Gbps transfer speed, double the rate of USB 3.2, which is the current spec, and eight times that of USB 3. That’s Ethernet speed and should be more than enough to keep your high-definition monitor fed with plenty of bandwidth for other data movement.
USB4 also has better resource allocation for video, so if you use a USB4 port to move video and data at the same time, the port will allocate bandwidth accordingly. This will allow a computer to use both an external GPU in a self-contained case, which have come to market only because of Thunderbolt 3, and an external SSD.
This could open up all kinds of new server designs because large, bulky devices, such as GPUs or other cards that won’t go easily into a 1U or 2U case, can now be externally attached and run at speeds comparable to an internal device.
Of course, it will be a while before we see PCs with USB4 ports, never mind servers. It took years to get USB 3 into PCs, and uptake for USB-C has been very slow. USB 2 thumb drives are still the bulk of the market for those devices, and motherboards are still shipping with USB 2 on them.
Still, USB4 has the potential to be a unifying interface that gets rid of bulky cables that have oversized plugs and provides throughput that can satisfy everyone from a laptop user to a server administrator.