USB 4.0

The USB Implementers Forum has announced the publication of USB4! The specification is available to download now as part of the document library of

USB Implementers Forum Announces the Publication of Its Thunderbolt 3-Based USB4 Standard article tells that USB 4 offers up to 40Gb/s throughput, PCI Express, and DisplayPort connectivity — plus compatibility back to USB 2.0.

USB4 is built around Intel’s Thunderbolt connectivity standard, which incorporates PCI Express and DisplayPort plus power delivery connectivity in a single cable.

USB4 is promised to be be fully backwards compatible with previous USB devices from the current top-end USB 3.2 Gen 2×2 standard down to USB 2.0 (though not now very rarely used USB 1.0). USB4 will be compatible with existing USB Type-C cables.


  1. Tomi Engdahl says:

    COM Express -kortit saavat nopeammat sarjaväylät

    COM Express on erittäin suosittu sulautettujen laitteiden korttiformaatti. Nyt alan standardeja kehittävä PICMG-konsortio on lanseerannut COM Expressiin uuden version 3.1. Se on ratifioitu tukemaan nopeita sarjaliitäntöjä, kuten PCIe Gen 4 ja USB4.

    Nämä uudet väylärajapinnat pidentävät COM Expressin käyttöaikaa johtavana Computer-on-Module (COM) -standardina erilaisissa suorituskykyisissä järjestelmissä. Nopeaa signalointia tukemaan on COM Expressin tyypin 6, 7 ja 10 liitäntöihin lisätty rinnalle 16 gigabitin liitin. Myös SATA Gen 3 -signaalin eheys- ja häviöbudjettitiedot on lisätty jokaiselle tyypille.

    Nämä parannukset liittyvät nastoituksen päivityksiin, mukaan lukien valinnainen USB4 (tyyppi 6), MIPI-CSI-liittimet (tyypit 6, 10), SoundWire (tyypit 6, 10) sekä ylimääräinen yleiskäyttöinen SPI-liitäntä (tyypit 6, 10). CEI-signalointia tukeva 10 GbE-liitäntä ja IPMB-hallintaliitäntä on myös nyt määritelty Type 7 -liitännässä osana COM.0 R3.1 -määritystä.

  2. Tomi Engdahl says:

    A key thing to note is that the standard is called “USB4,” not “USB 4.0″ or “USB 4,” and the USB-IF actually has two marketing names for USB4, namely “USB4 20 Gbps” and “USB4 40 Gbps.” The technical names are “USB4 Gen 2×2″ and “USB Gen 3×2,” but there’s also “USB4 Gen 2×1″ and “USB4 Gen 3×1,” both of which are fallback protocols in case of interference or a bad cable, and both rely on a single cable pair. Normally, both cable pairs are used, so using just one cable pair will cut speeds in half.

    USB4 has to support at least one display output, but unlike previous USB standards, the DisplayPort signal is tunnelled rather than using DP Alt Mode. That said, DP Alt Mode is still supported for older devices, as well as for DP 2.0 devices. The advantage of tunnelling is that a single cable can in theory transmit USB4, DisplayPort, and PCIe signals at the same time, something that wasn’t possible with previous versions of USB. This is also how Thunderbolt 4 works and why the two standards are so similar.

    Unlike DP Alt Mode, which physically takes over two wire pairs of the four pairs in a USB Type-C cable for exclusive use for DisplayPort signals, tunnelling allows the DP 1.4 signal to be transmitted simultaneously with USB4 or PCIe signals.

  3. Tomi Engdahl says:

    PICMG consortium ratifies COM Express 3.1 to support high-speed serial interfaces

    WAKEFIELD, Mass. The PICMG consortium has ratified the new COM Express 3.1 specification to support high-speed serial interfaces such as PCIe Gen 4 and USB4.

    To support this high-speed signaling, an updated 16 Gb/sec connector has been specified across the family’s Type 6, 7, and 10 pinouts and added SATA Gen 3 signal-integrity and loss budget information. These improvements join pinout-specific upgrades including optional USB4 (Type 6), MIPI-CSI connectors (Types 6, 10), SoundWire (Types 6, 10), as well as an additional general-purpose SPI interface (Types 6, 10). A CEI signaling-enabled 10 GbE interface and IPMB management interface are also now defined in the Type 7 pinout as part of COM.0 R3.1.

    Jeff Munch, CTO of Adlink Technology and chairman of the COM Express subcommittee, said of the newly ratified 3.1 standard: “In the latest release of the COM Express specification, the subcommittee has added support for PCI Express Gen 4, USB4, and newer 10G side-band interfaces while maximizing backwards compatibility.”

    PICMG® Releases Its Newest COM.0 R3.1 Spec for COM Express to Include PCIe Gen 4 and USB 4.0 Support
    COM Express R3.1 Compliant Modules — ADLINK Express-ADP Type 6 Basic size and Express-ID7 Type 7 Basic size Now Available

    Compared to R3.0, Revision 3.1 has added support for several advanced interfaces suitable for next-gen AIoT applications, such as PCIe Gen 4 support across all module types, USB4 for Type 6 and adding a second PCIe Clock while updating 10G Ethernet to support CEI side-band signaling for Type 7. Other enhancements include adding options for general purpose SPI, MIPI-CSI connectors, and SoundWire, as well as adding IPMB for Type 7.

    ADLINK Express-ADP Type 6 Basic size utilizes 12th Gen Intel® Core™ processors based on advanced hybrid architecture with up to 6 Performance-cores (P-cores) and 8 Efficient-cores (E-cores), effectively boosting productivity and fueling IoT innovation across a wide variety of deployments. It provides DDR5 memory support with up to 4800 MT/s combined with increased cache, and integrated Intel® Iris® Xe graphics with up to 96EUs, to offer four concurrent 4K60 HDR displays and Intel® Deep Learning Boost for superior AI performance. Using DDI, eDP 1.4b and USB4/TBT4, the four independent displays support Display Alternative mode, the module provides premium graphics features for superior content support, display and I/O virtualization.

  4. Tomi Engdahl says:

    USB4 is a Glorious Mess

    USB has never been easy to understand, and USB4 is no exception. How compatible is it with Thunderbolt 3? What about Thunderbolt 4? What cables can and can’t be used? Is a USB4 cable interchangeable with a Thunderbolt 4 cable?

    0:00 USB 4 is soooo confusing
    1:25 What is USB 4?
    4:47 Connecting TB devices to USB4 ports
    7:30 MacOS vs. Windows
    9:47 Older TB product compatibility
    10:32 Daisy Chaining
    12:38 External GPU
    13:17 Watch Linus break things
    15:39 Is USB4 compatible with TB3/4 devices?


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