It’s that time again—another USB standard is upon us, ready to upgrade your device’s ports and cabling in the coming years. Here we’re going to explain everything you need to know about USB4, including the speed improvements in the pipeline and the new capabilities it’s going to borrow from Thunderbolt 3, which shares the same port shape but is a different and more demanding protocol that can piggyback on top of USB-C ports.
If you’re a little confused about where we’re up to, the latest standard actually in use is USB 3.1, though you won’t find too many devices using it (the latest MacBook Pro models do). The USB 3.2 standard has been confirmed in terms of its technical aspects but isn’t actually going to appear in consumer devices until later this year.
So while we’re waiting for USB 3.2 to arrive, what better time to announce USB4? The USB Promoter Group has just pushed out details of the new technology and removed the space between the word and the version number too. To muddy the waters even further, the group is now referring to USB 3.0 as USB 3.2 Gen 1, and to USB 3.1 as USB 3.2 Gen 2. That shouldn’t make it more difficult!
The latest USB 3.2 is technically USB 3.2 Gen 2x2—that “2x2" refers to the ability to use two high-speed channels on the same cable, for a maximum throughput of 20Gbps. USB 3.1 (USB 3.2 Gen 2) tops out at 10Gbps, while USB 3.0 (USB 3.2 Gen 1) tops out at 5Gbps. Our friends at Lifehacker on more on the renaming kerfuffle here.
Note too that the actual port shape and standard is separate from the underlying USB protocol, although they’re often developed in tandem (USB 3.2 Gen 2x2 needs a USB-C connector, for example). In other words, not all USB-C plugs have the same USB tech inside them—manufacturers can make different choices about the speeds they want and the costs they want to pay.
To support a particular USB standard, you need a device (a computer or a phone, say), a USB connector port and a cable that all support it, otherwise, the speeds will drop back to a slower level.
With all of that mess and confusing preamble out of the way, what does USB4 bring us? The headline news is that bandwidth gets doubled again, so we’re talking a maximum of 40Gbps throughput. If you’re not familiar with the terms, bandwidth is like the number of lanes on a highway—its potential capacity—whereas throughput is how many cars can actually travel (or are actually traveling) at one time.
Throughput (actual speeds) will always be equal to or less than bandwidth (theoretical speeds) depending on all kinds of factors, including the devices you’re using. If you’re using USB4 ports, cables, and devices, you’ll be able to hit the maximum 40Gbps of throughput that the bandwidth allows.
On top of that, Intel is throwing in its Thunderbolt 3 standard as part of the USB4 protocol, which means the potential to daisy-chain 4K monitors and other devices together without the aid of a hub—something USB hasn’t done before.
It essentially means Thunderbolt 3 is going to be built right into USB4, leading to more versatility in terms of data transfer rates when using multiple devices together. While Apple Macs have combined Thunderbolt 3 and USB together to some extent, the technology is still relatively rare on PCs and other devices.
In the words of the official press release, USB4 “defines a method to share a single high-speed link with multiple end device types dynamically that best serves the transfer of data by type and application”—so think multiple external displays and other devices like hard drives connected over one cable or one chain of cables rather than a hub.
The good news is that everything is going to be backward compatible with USB 2, USB 3 and Thunderbolt 3—your existing devices will still be able to talk to USB4 hardware, they’ll just have to do it at a slower speed.
Daisy-chained devices, twice the bandwidth, more versatility, Thunderbolt 3 integration... USB4 looks set to earn the jump up from 3.2 in the official nomenclature (though we’re still not sure about the lack of a space).
So when will you be able to get your hands on this magical new transfer standard? The USB4 spec is expected to be formally finalized and published in the middle of 2019 (when USB 3.2 devices should start trickling out). At the same time, the USB-C standard should also see an update to match USB4. Depending on manufacturers and the sort of market demand they see, USB4 hardware should start appearing near the end of 2020.
The USB Promoter Group is made up of representatives from Apple, HP, Intel, Microsoft, Renesas Electronics, ST Microelectronics, and Texas Instruments, so there will be some big names behind the future roll out. The group is backed up by the non-profit organization the USB Implementers Forum (USB-IF), which handles certification and so on.
Still to be confirmed is the official marketing name which you might see on packaging—at the moment we have SuperSpeed USB (USB 3.0 or USB 3.2 Gen 1), SuperSpeed 10Gbps (USB 3.1 or USB 3.2 Gen 2), and SuperSpeed 20Gbps (USB 3.2 Gen 2x2). Don’t hold your breath for the naming conventions to get simpler any time soon—maybe the USB-IF should follow the lead of the Wi-Fi Alliance.