Fulfilling its 2017 promise to make Thunderbolt 3 royalty-free, Intel has given the specification for its high-speed interconnect to the USB Implementers Forum (USB-IF), the industry group that develops the USB specification. The USB-IF has taken the spec and will use it to form the basis of USB4, the next iteration of USB following USB 3.2.
Thunderbolt 3 not only doubles the bandwidth of USB 3.2 Gen 2×2, going from 20Gb/s to 40Gb/s, it also enables the use of multiple data and display protocols simultaneously. We would expect the USB4 specification to be essentially a superset of the Thunderbolt 3 and USB 3.2 specifications, thus incorporating both the traditional USB family of protocols (up to and including the USB 3.2 Gen 2×2) and the Thunderbolt 3 protocol in a single document. Down the line, this should translate into USB4 controllers that support the whole range of speeds.
Lost? Frightened? Confused? Good!
People already get the names wrong, so the USB group has doubled down on bad naming.
USB 3.0 was straightforward enough. A USB 3.0 connection ran at 5Gb/s, and slower connections were USB 2 or even USB 1.1. The new 5Gb/s data rate was branded "SuperSpeed USB," following USB 2's 480Mb/s "High Speed" and USB 1.1's 12Mb/s "Full Speed."
But then USB 3.1 came along and muddied the waters. Its big new feature was doubling the data rate to 10Gb/s. The logical thing would have been to identify existing 5Gb/s devices as "USB 3.0" and new 10Gb/s devices as "USB 3.1." But that's not what the USB-IF did. For reasons that remain hard to understand, the decision was made to retroactively rebrand USB 3.0: 5Gb/s 3.0 connections became "USB 3.1 Gen 1," with the 10Gb/s connections being "USB 3.1 Gen 2." The consumer branding is "SuperSpeed USB 10Gbps."
What this branding meant is that many manufacturers say that a device supports "USB 3.1" even if it's only a "USB 3.1 Gen 1" device running at 5Gb/s. Meanwhile, other manufacturers do the sensible thing: they use "USB 3.0" to denote 5Gb/s devices and reserve "USB 3.1" for 10Gb/s parts.
USB 3.2 doubles down on this confusion. 5Gb/s devices are now "USB 3.2 Gen 1." 10Gb/s devices become "USB 3.2 Gen 2." And 20Gb/s devices will be... "USB 3.2 Gen 2×2." Because they work by running two 10Gb/s connections along different pairs of wires simultaneously, and it's just obvious from arithmetic that you'd number the generations "1, 2, 2×2." Perhaps they're named for powers of two, starting with zero? The consumer branding is a more reasonable "SuperSpeed USB 20Gbps."
-- submitted from IRC
As the tech industry gears up for the launch of the new USB4 standard, a few more parts first need to fall into place. Along with the core specification itself, there is the matter of alternate modes, which add further functionality to USB Type-C host ports by allowing the data pins to be used to carry other types of signals. Keeping pace with the updates to USB4, some of the alt modes are being updated as well, and this process is starting with the granddaddy of them all: DisplayPort Alt Mode.
The very first USB-C alt mode, DisplayPort Alt Mode was introduced in 2014. By remapping the USB-C high speed data pins from USB data to DisplayPort data, it became possible to use a USB-C port as a DisplayPort video output, and in some cases even mix the two to get both USB 3.x signaling and DisplayPort signaling over the same cable. As a result of DisplayPort Alt Mode's release, the number of devices with video output has exploded, and in laptops especially, this has become the preferred mode for driving video outputs when a laptop doesn't include a dedicated HDMI port.
If you're willing to accept Display Stream Compression... New DisplayPort spec enables 16K video over USB-C
Previously: Forget USB 3.2: Thunderbolt 3 Will Become the Basis of USB 4
DisplayPort 2.0 Announced, Triples Bandwidth to ~77.4 Gbps for 8K Displays
Speed-Doubling USB4 is Ready -- Now We Just Have to Wait for Devices