USB4 Spec Published

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The USB Implementer's Forum (USB-IF), responsible for creating USB specifications, today published the USB4 spec. Besides removing the space from its naming system, USB4 offers twice as much bandwidth as USB 3.2, resulting in a maximum throughput of 40 Gbps when using appropriately certified cables.

USB-IF announced the USB4 spec in March. In addition to increased throughput, USB4 offers "the ability to optimally scale allocations for display data flow," which makes it possible to daisy chain devices even if they're a mix of external displays and data-driven devices, like external storage. The next-generation USB interface will also be backwards compatible with USB 2, USB 3.2 and Thunderbolt 3.

Swipe to scroll horizontally
SpecificationThroughputPrevious TermTechnical TermMarketing Term
USB 440 GbpsN/AUSB 4.0Not Announced
USB 3.220 GbpsN/AUSB 3.2 Gen 2x2SuperSpeed USB 20Gbps
USB 3.110 GbpsUSB 3.1 Gen 2USB 3.2 Gen 2SuperSpeed USB 10Gbps
USB 3.05 GbpsUSB 3.1 Gen 1USB 3.2 Gen 1SuperSpeed USB

The backwards compatibility with Thunderbolt 3--along with some of the improvements made to USB4 as a whole--results from Intel contributing its Thunderbolt technology to the USB specification. That means Thunderbolt-compatible products will no longer have to pay the company a licensing fee, too, which should incentivize manufacturers to adopt Thunderbolt in their products sooner than later.

USB-IF plans to announce a new specification for the USB Type-C connector to handle USB4 bus delivery (the backwards compatibility wouldn't mean that much to most people if they had to deal with yet another connector type). The group plans to reveal more about its plans for USB4, USB Type-C, USB Power Delivery and "new USB-IF branding strategies" at the USB Developer Days conferences in Seattle and Taipei later this year.

Check out our summary of everything we know about USB4 for more information.

Nathaniel Mott
Nathaniel Mott
Freelance News & Features Writer

Nathaniel Mott is a freelance news and features writer for Tom's Hardware US, covering breaking news, security, and the silliest aspects of the tech industry.

8 Comments Comment from the forums
  • daglesj
    I kind of lost interest after USB Superspeed came out. Until we can transfer modern softwares need for tens of thousands of microfiles at 500MBps instead of 5KBps, any increment is largely just garnish.

    Funny how no one bothers to address this issue. Sure I can shift 4K video files at 1000MBps all day long but real world mixed micro data...crawl!
    Reply
  • InvalidError
    If the Type-C spec has to be updated to make it compatible with TB3 and require TB3 cables to work, then we're back to the hellish place of cables not being anywhere near universal.

    How many different permutations of Type-C do we have now?
    power only
    USB1.x/2 only
    USB3 (singe set of high-speed pairs)
    USB3.2x2 (two sets of pairs)
    USB4.0 (double 2x2 speed)
    alt-modes
    I bet I'm missing a few. Better not get your type-C cables mixed up if you don't want to hamstring your higher-speed devices. I'm quite disappointed with how non-universal and cluttered type-C has turned out. I think we're due for a clean slate dedicated to high-speed data bus. I'm thinking along the line of PnP PCIe over fiber. Displays could still connect to this, just need to make them PCIe data sinks and point the GPU's display engine to the monitor's PCIe address, no need for DP encapsulation.
    Reply
  • daglesj
    InvalidError said:
    If the Type-C spec has to be updated to make it compatible with TB3 and require TB3 cables to work, then we're back to the hellish place of cables not being anywhere near universal.

    How many different permutations of Type-C do we have now?
    power only
    USB1.x/2 only
    USB3 (singe set of high-speed pairs)
    USB3.2x2 (two sets of pairs)
    USB4.0 (double 2x2 speed)
    alt-modesI bet I'm missing a few. Better not get your type-C cables mixed up if you don't want to hamstring your higher-speed devices. I'm quite disappointed with how non-universal and cluttered type-C has turned out. I think we're due for a clean slate dedicated to high-speed data bus. I'm thinking along the line of PnP PCIe over fiber. Displays could still connect to this, just need to make them PCIe data sinks and point the GPU's display engine to the monitor's PCIe address, no need for DP encapsulation.


    Yeah it's a mess. All I want to do with it is push as much data through it as possible. I don't want to run 4K video, a 2080 GPU, mining cluster or fridge freezer off the damn thing.
    Reply
  • regs01
    Looks like they keep smoking a lot with this nomenclature. Or they do it intentionally. Either they hate people, so they trying to do worse for us, or either they intentionally helping manufacturers to trick customers with this numbers, pushing people into buying 10 gbit when they need 20 gbit or 20 gbit when they need 40 gbit.
    Reply
  • GetSmart
    Should be preferably 40Gbps (such as in Thunderbolt 3 specifications), otherwise its pretty pointless. And making the USB4 devices Thunderbolt 3 compatible (with dual mode) will also help.
    Reply
  • InvalidError
    regs01 said:
    they intentionally helping manufacturers to trick customers with this numbers, pushing people into buying 10 gbit when they need 20 gbit or 20 gbit when they need 40 gbit.
    Downselling? It usually goes the other way around: trick people into buying overpriced next-gen stuff they aren't going to need within the system's useful life. It does not work anywhere near as well the other way around since the slower stuff isn't a distinguishing feature that companies can charge extra for anymore.
    Reply
  • regs01
    Menufacturers would save costs on manufacturing. 3.2 is cheaper than 4.0 and 3.1 is cheaper than 3.2, kind of.
    Reply
  • joevt1
    InvalidError said:
    If the Type-C spec has to be updated to make it compatible with TB3 and require TB3 cables to work, then we're back to the hellish place of cables not being anywhere near universal.

    How many different permutations of Type-C do we have now?
    power only
    USB1.x/2 only
    USB3 (singe set of high-speed pairs)
    USB3.2x2 (two sets of pairs)
    USB4.0 (double 2x2 speed)
    alt-modesI bet I'm missing a few.
    I don't think "USB3 (single set of high-speed pairs)" is an option. A cable requires all four pairs because USB-C is reversible.

    Some other options: I believe there are different cables for 5 Gbps and 10 Gbps per lane. And different cables for different power delivery options.

    The only alt modes I know that require special cables are Thunderbolt (40Gbps) and VirtualLink. I think USB4 (40Gbps) should be able to work with existing Thunderbolt 40Gbps cables (they both use 20 Gbps per lane). VirtualLink is interesting because it changes the USB2 lines to be capable of transmitting USB3 gen 2.

    The cable variations allow the consumer to to choose the least capable (therefore least expensive) cable for their need.
    Reply