Back in 2017, Intel announced that Thunderbolt 3 would be a royalty-free standard, to encourage wider adoption and improve availability. TB3 was a significant step forward for Intel and its high-speed protocol in another sense as well — it offered USB-C compatibility, simplifying the number of cables and adapters people had to carry. Now, Intel has followed through on its promise to make the standard royalty-free and the USB-IF has announced (obliquely) why it used such confusing terminology for the upcoming USB 3.2. Going forward, Thunderbolt 3 will become USB 4.
The immediate implications of this are a further doubling of bus performance, up to 40Gbps. TB3 also allowed for the use of multiple devices and protocols simultaneously.
Past this point, there are questions about what, exactly, it means for USB to absorb Thunderbolt. Unlike USB, Thunderbolt functions as a physical extension of the PCIe bus. There are certain applications and capabilities that run significantly better as a result, either because they benefit from decreased latency and higher bandwidth available in that mode, or because USB doesn’t support certain functions natively. We’re less concerned with backward compatibility — the report indicates this will be preserved for both previous USB devices and older Thunderbolt hardware — but curious about what this will mean for future USB4 devices. It’s possible we’ll see some feature improvements linked to enhancements gained from shifting from USB to Thunderbolt as well.
There’s a certain irony in all of this, to be sure. When Thunderbolt shipped, it was generally dismissed because USB 3 would provide as much performance as people needed at a fraction of the price. Instead, Thunderbolt 3 will essentially become the next version of the USB standard. Intel intends to start integrating TB3 more widely with Ice Lake. With the standard coming out now, it’s likely that we’ll see product integration in ~2021.
This raises an interesting point of its own. USB 3.2 support isn’t even expected until 2020, so the lifespan of USB 3.2, specifically, is likely to be very short. We may see only a handful of motherboards even bother to bring that feature to market. Intel and AMD will both have good reason to bring USB4 out as quickly as possible — Intel, of course, is positioning its own standard as front-and-center in the market, while AMD will be able to position its own implementation for the first time. Given that AMD is also expected to update its own compute platforms in 2021 for the first time since Ryzen, it would make sense for the company to tackle USB4, DDR5 (maybe) and any other I/O changes it wants to make all at once, top-to-bottom.
The USB-IF hasn’t yet acknowledged if we’ll see a new round of renamed USB 3.x products once USB4 drops. Given the organization’s behavior to-date, we wouldn’t be surprised.