USB has undergone a couple of big changes recently, what with the introduction of USB 3.2, the renaming of previous USB specifications, and the announcement of the USB4 standard. Let’s try to simplify them here and what it means for users.
First, here's a table that gives an overview of the new names and their old names. I'll expound on them below.
|New name||Old name||Original name||Marketing name||Maximum throughput||Connector|
|USB 3.2 Gen 1||USB 3.1 Gen 1||USB 3.0||SuperSpeed USB||5Gbps||USB-C/A|
|USB 3.2 Gen 2||USB 3.1 Gen 2||USB 3.1||SuperSpeed USB 10Gbps||10Gbps||USB-C/A|
|USB 3.2 Gen 2x2||N.A||USB 3.2||SuperSpeed USB 20Gbps||20Gbps||USB-C|
This is what used to be known as USB 3.1 Gen 1 which was previously known simply as USB 3.0 The maximum transfer speed is 5Gbps and it can use either a USB-C or USB-A connector. You will see it being marketed on devices under the name SuperSpeed USB.
This is what used to be known as USB 3.1 Gen 2. The maximum transfer speed is 10Gbps and it can use either a USB-C or USB-A connector. You will see it being marketed on devices under the name SuperSpeed USB 10Gbps or SupserSpeed+ USB 10Gbps.
USB 3.2 has been talked about since 2017 and it is finally here. This is the latest specification of the USB 3.xx group of standards and it promises transfer speeds of up to 20Gbps - the maximum attainable on a USB-C cable. It achieves this using two high-speed USB-C channels. You will see it being marketed on devices under the name SuperSpeed USB 20Gbps. USB 3.2 Gen 2x2 will only be available using a USB-C connector.
Intel promised that it would make Thunderbolt 3 open and royalty free and it has finally happened. USB4 (yes, without a space) is based on the Thunderbolt 3 protocol and it supports all the good things that Thunderbolt 3 can. This means a maximum data transfer rate of 40Gbps, power delivery of up to 100W, and the ability to drive two 4K displays or a single 5K display. On top of that, it will also be backward compatible with older USB standards such as USB 3 and 2. Finally, note that USB4 only use a USB-C connector.
There are, however, some caveats. First of all, you need a good quality cable to achieve the maximum data transfer rate of 40Gbps. That said, older cables will work but they will only operate at their maximum rated speeds. So an old USB 3.0 cable will only get 5Gbps even if it is plugged into a USB4-capable port.
While USB4 is based on the Thunderbolt 3 protocol, it is not clear at this point if all USB4 implementations will work with properly with Thunderbolt 3 devices. This is because Thunderbolt compatibility is not a requirement of the USB4 specification. Furthermore, any product that wants to market itself as Thunderbolt compatible needs to be certified by Intel. Manufacturers might choose not to do that as products need to undergo a rigorous validation process that adds cost to the product. That said, the USB Promoter Group expects most USB4 devices to work well with Thunderbolt 3. But, no guarantees.
The biggest winner out of this is Thunderbolt 3. Because Thunderbolt 3 will fully support all USB standards including USB4, USB 3, and USB 2. So if your device has a Thunderbolt 3 port, it will work with USB4 devices of the future.