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USB4 converges the Thunderbolt and USB protocols as part of Intel’s goal to make Thunderbolt available on a royalty-free basis, which should result in wider and cheaper availability of Thunderbolt accessories like docks and eGPUs.
As USB4 is based on Thunderbolt 3, it offers data transfer speeds up to 40 Gbps, which is twice as fast as the bandwidth of the latest USB 3.2 Gen 2×2 specification. USB4’s underlying Thunderbolt 3 protocol also means the specification supports up to two 4K displays or one 5K display over a single cable.
The simplest way to view USB4 is as Thunderbolt 3, but royalty free for manufacturers. Intel will continue to offer Thunderbolt 3 on a standalone basis with a few advantages over USB4, including more support with reference designs and technical issues for manufacturers, according to The Verge.
USB4 will use the USB-C connector design and will be backwards compatible with USB 3.2 and USB 2.0 specifications.
The USB4 specification is on track to be published around the middle of 2019. Over 50 companies are actively participating in the final stages of review of the draft specification, which should include Apple, Intel, and Microsoft, but it might take a few years until the first USB4 devices are released.
