Thunderbolt-based USB4: backward compatible, speed gains and more

The USB Promoter Group revealed information about the upcoming USB4 specification today in a press release.

In short: USB4 is based on Thunderbolt, backwards compatible with USB 3.2, 2.0, and Thunderbolt 3, and about twice as fast as USB 3.2 Gen2x2.

When USB 3.0 was introduced back in 2009, it was an improvement in all regards compared to the-then dominating standard USB 2.0. USB 3.1 and 3.2 were introduced in the years that followed; each a step up in terms of performance and data transfer rates over the previous standard.

Not all is golden today though. Not all new devices that come on the market support the latest USB versions. It is not uncommon, especially for low-end devices, to only support USB 2.0, or include more USB 2.0 ports than USB 3.0 ports. It does not help either that the names that the USB Promoter Group picked for the individual specifications are confusing, and that people had to deal with different cables and connectors next on top of that.

To add even more icing to the cake, it was announced recently that USB terms would be rebranded: USB 3.0 to USB 3.2 Gen 1 and the marketing term SuperSpeed USB, USB 3.1 to USB 3.2 Gen 2 and the marketing term SuperSpeed USb 10Gbps, and USB 3.2 to USB 3.2 Gen 2×2 and the marketing term SuperSpeed USB 20Gbps.


Today’s announcement adds USB4 to list of available USB versions. USB4 is based on Intel’s Thunderbolt technology. Intel made Thunderbolt 3 royalty-free and the USB Promoter Group uses the Thunderbolt specification as the base for USB4.

USB4 offers double the bandwidth of USB 3.2 Gen2x2, and the same as Thunderbolt 3 which Intel launched in 2015. The standard supports up to 40GB/s opposed to 20GB/s which USB 3.2 supported. The upcoming version features additional improvements such as efficient options to share multiple data an display protocols.

USB4 uses USB Type C which was introduced with USB 3.2 Gen2. Intel plans to integrate support for Thunderbolt 3 and USB4 natively into upcoming products. It is likely that other manufacturers will do the same eventually thanks to the royalty-free nature of USB4.

The new USB4 architecture defines a method to share a single high-speed link with multiple end device types dynamically that best serves the transfer of data by type and application. As the USB Type-C™ connector has evolved into the role as the external display port of many host products, the USB4 specification provides the host the ability to optimally scale allocations for display data flow. Even as the USB4 specification introduces a new underlying protocol, compatibility with existing USB 3.2, USB 2.0 and Thunderbolt 3 hosts and devices is supported; the resulting connection scales to the best mutual capability of the devices being connected.

Closing Words

The specification has not been released officially yet; while it is possible that things may change before that happens, it seems unlikely that this is going to happen.

The announcement leaves some questions unanswered:

  1. When will the first consumer devices with USB4 support be released?
  2. Will USB 3.2 Gen2x2 be dead on arrival?

Now You: What is your take on the USB standard and the new USB4?

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