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USB4: everything you need to know

USB-C port on Apple MacBook 2016
(Image credit: Future)

USB4 is a new standard of connectivity, which at the time of writing has just had its specification officially confirmed by the USB Implementers Forum (USB-IF), the tech standards non-profit which is guardian and cheerleader of all things USB (Universal Serial Bus).

So what are the specs, how fast is USB4, what else does it do, and what will it really mean for you going forward? In this article, we’re going to cover all the essentials you need to know about this latest USB standard.

Starting off with the observation that the road to USB4 has been a long and confusingly signposted one. If you’ve been following the previous shenanigans of USB-IF, you’ll likely be all too familiar with the baffling naming schemes which have crazily-paved this particular avenue.

We had USB 3.1 Gen 1 (offering data transfer speeds of 5Gbps) and USB 3.1 Gen 2 (10Gbps), which recently became USB 3.2 Gen 1 and USB 3.2 Gen 2 respectively, following the introduction of a new USB 3.2 Gen 2x2 standard early in 2019 which boosted speeds to 20Gbps.

It’s all rather messy on the chopping and changing of names with ‘Gen’ suffixes, then, but the basic gist is that these cables represent 5Gbps, 10Gbps, and 20Gbps speeds, and USB-IF has suggested they are referred to as SuperSpeed USB, SuperSpeed USB 10Gbps and SuperSpeed USB 20Gbps respectively.

There are other nuances to bear in mind, such as the fact that SuperSpeed USB 20Gbps (USB 3.2 Gen 2x2) requires a USB Type-C connector (the previous incarnations don’t), but let’s not get too wrapped up in the old standards here.

USB4 moves things on from USB 3.2 Gen 2x2 in a big way, doubling speeds up again to 40Gbps – data transfer levels previously only available to those using Thunderbolt 3 technology, which the new USB standard is built on – but there’s more to this picture than just pure speed, as we’ll explore below.

Cut to the chase

  • What is it? Next-gen USB standard that follows on from USB 3.2
  • When is it out? The first USB4 devices should emerge later in 2020
  • What will it cost? Unknown as yet – but cables won’t be cheap

USB4 release date

The new standard was first announced back in March 2019, and at the time of writing, has just had the spec officially confirmed by USB-IF. So manufacturers can now begin work on producing devices, but obviously that process will take time – and at this point, we don’t have any exact timeframe. It’s a bit of a case of: how long is a USB lead?

All we can really do is point to the broad expectation that the first USB4 kit will be pitching up in around a year, at some point later in 2020, although that could slide to the following year.

(Image credit: USBIF)

USB4 spec and performance

As we mentioned at the outset, USB4 is based on the Thunderbolt protocol which Intel made freely available to the USB Promoter Group (which it’s a member of, along with many other tech giants), allowing USB4 to offer Thunderbolt 3 equivalent speeds of 40Gbps; twice that of the preceding USB 3.2 Gen 2x2 standard.

So, USB4 is bringing this much faster level of performance to all vendors across the board, whereas previously, this could only be achieved by those manufacturers willing to work directly with Intel (and pay royalties) to incorporate Thunderbolt 3 into their hardware. That’s obviously a majorly beneficial stride forward in opening up the world of super-speedy 40Gbps connectivity.

However, it isn’t quite as simple as everyone suddenly being able to benefit from 40Gbps data transfer speeds going forward. More on that later, but first let’s concentrate on detailing the rest of the spec, speed levels aside.

In terms of compatibility with older standards, USB4 will be backward compatible with USB 3.2 and devices going back to USB 2.0 (although you will need an adapter to plug the USB4 cable – which exclusively uses a Type-C connector, like USB 3.2 Gen 2x2 – into old USB ports, of course).

USB4 is also designed to be compatible with Thunderbolt 3, although we should note it’s up to the device manufacturer to implement that compatibility – a decision made because the likes of smartphone makers won’t want to. So while this isn’t a hard-and-fast rule, it’s expected that PC vendors will include Thunderbolt 3, although that doesn’t have to be the case – and thus there could be a bit of confusion therein.

As we’ve said, the new standard isn’t just about speed, and USB-IF has further clarified that USB4 will involve “multiple data and display protocols that efficiently share the maximum aggregate bandwidth”. With USB4, you will be able to hook up a pair of 4K monitors (at 60Hz) to your PC (or one 5K display), for example, and it’s fast enough to connect an external GPU. For power delivery, like Thunderbolt 3, we’re looking at 100W of juice.

Also note that the mentioned more ‘efficient sharing’ means that USB4 doesn’t waste any bandwidth when sending multiple signals down the cable. So if you’ve got a monitor plugged in and a video signal being sent, alongside data, the former will only use the bandwidth it needs (whereas previously with USB 3, that video signal could hog more bandwidth than it actually required, effectively robbing you of data transfer speed when performing multiple operations).

Overall, the broad idea is to deliver everything Thunderbolt 3 has been offering, and a bit more, except unified across all PCs, devices and accessories, with one standard – albeit with slight variances such as whether Thunderbolt 3 compatibility is incorporated – using one connector (USB Type-C).

MacBook Pro (13-inch, 2019)

(Image credit: Future)

USB4 pricing issues

That overarching plan to eventually transition all devices across to using Type-C connectors and USB4 is a laudable goal, but obviously that won’t happen anytime soon. While the first USB4 devices should emerge in 2020, widespread adoption of the standard will be a lot further away, and likely a very slow process for price-related reasons.

Naturally, to drive adoption, device manufacturers will have to produce hardware which has USB4 ports, and these cost more than the previous-gen tech to implement.

This cost issue – which will doubtless be more pronounced in the early stages of USB4 development – means that older USB ports will likely hang around for some time yet (as we’ve already seen since the introduction of USB Type-C). Remember that the fancy new (more expensive) USB4 connectors won’t be needed for all use cases, such as hooking up a simple keyboard – which doesn’t need great chunks of bandwidth – so older-gen USB ports will still be included, probably in the majority, on desktop PCs and laptops; at least in the nearer future.

The other cost issue with USB4 is the cables. These will be considerably more expensive than previous USB leads, as they need to be higher quality ‘40Gbps certified’ cables to successfully carry all that bandwidth.

So this is how pricing issues on the manufacturer’s side are going to be something of a drag on that grand vision of an all-USB4 computing world, where all connectivity is uniform.

The positive point regarding pricing is that at least USB4 represents a new, open and royalty-free way forward, compared to Thunderbolt 3 with its Intel tax which made implementation an even costlier proposition (and indeed truly widespread adoption impossible due to being tied in with Intel technology).

The USB4 switchover will take time – and a lot of it, no doubt – but it will eventually start to gain serious momentum. However, in this prolonged transitional phase, further confusion is likely to come into play in terms of the capabilities of any particular given USB Type-C connector (although there’s nothing new there), which might be USB4, USB4 without Thunderbolt 3 compatibility, or a previous-gen technology.