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The USB Developer Forum has released the USB4 specification, as promised, but with disappointment: Thunderbolt support is optional, which means there may be confusion about which devices can support the chosen protocol.
When the USB4 specification was announced, the revelation was to incorporate the Thunderbolt 3 specification for the display and data connectivity developed by Intel. Intel had then announced that it would bring the Thunderbolt specification to the USB developer group, and a spokesman confirmed it. Intel also said the new high-speed 40Gbps protocol would use a USB-C cable. All this seems to be true.
But the assumption that USB4 would still include Thunderbolt is, according to the specification, not always true. The published specification clearly shows that it is up to USB4 device manufacturers to support Thunderbolt.
For its part, the USB developer forum has issued a lengthy statement clarifying the problem and clearly indicating that many PC vendors would at least support a common USB / Thunderbolt implementation.
"Regarding optional support for Thunderbolt 3 through the USB4 specification, USB-IF expects PC vendors to widely support Thunderbolt 3 compatibility in their USB4 solutions, since Thunderbolt 3 compatibility is now included in the USB4 specification and therefore free of rights for formal adopters, "the USB-IF said in a statement. "That being said, Intel still retains the Thunderbolt 3 mark / certification so that consumers can search for the appropriate Thunderbolt 3 logo and brand name to ensure that the USB4 product in question has the expected Thunderbolt 3 compatibility. The decision was made not to use Thunderbolt 3 compatibility a requirement of the USB4 specification as some manufacturers (smartphone manufacturers, for example) will probably not need to add additional features provided by the compatibility Thunderbolt 3 when designing their USB4 products. "
Labeling can be a problem
Unfortunately, it does not help to understand what a USB-C port means when the consumer sees it on a laptop. Does it use USB 3.2 Gen 2×2, or just Gen 2? Or the new USB4, also called USB Gen3x2? Does this include Thunderbolt 3? Power delivery? DisplayPort?
Technically, there are some differences between USB4 and Thunderbolt, which device manufacturers have to take into account. Signaling speeds for USB devices are 10 Gbps for Generation 2 USB devices and 20 Gbps for Generation 3 devices. However, device manufacturers who choose to support Thunderbolt must support compatible bit rates. Thunderbolt 3 of 10.3125 Gbps (for Generation 2) and 20.625 Gbps (for Generation 3).
Otherwise there is really no difference between USB 3.2 and USB4, as far as the data architecture is concerned – it is still based on what the US-IF calls "Enhanced SuperSpeed USB", in accordance with the specification.
"The difference between USB4 and USB 3.2 is that USB4 is a connection-oriented tunneling architecture designed to combine multiple protocols on a single physical interface, so that the speed and total performance of the USB4 Fabric can be shared in ways that dynamic, "he says. If said. "USB4 allows USB data transfers to work in parallel with other independent protocols specific to display, load / storage, and host-to-host interfaces." In addition, USB4 extends performance beyond 20 Gbps (2 x 2 generation) USB 3.2 interfaces to 40 Gbps (3 x 2 generation) on the same dual-channel and dual-simplex architecture. "
Unfortunately, this has little consolation when we try to understand the USB-C ports that are becoming more prevalent on the side of laptops. A single-size USB-C connector seems a good thing, but hardware manufacturers will have to clearly indicate the capacity of each connector, otherwise they may frustrate customers who simply do not know what port is doing what.
This story was updated at 16:56 with an additional comment from the USB-IF.
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