What Thunderbolt 4 Means and How It Could Change Computing

There's still confusion over how Thunderbolt 3 and USB-C fit together. (Image: Thunderbolt)
There's still confusion over how Thunderbolt 3 and USB-C fit together. (Image: Thunderbolt)

Technology standards don’t stay still for very long, whether it’s USB, DisplayPort, or wifi, they’re constantly gaining new abilities and a new number tacked to the end of their names. The latest protocol to edge its way to the consumer masses is Thunderbolt 4. Its arrival is likely to have a big impact on the laptop and desktop computer market, and here’s everything you need to know about it.

If you’re completely new to Thunderbolt, a quick-ish recap: It’s a hardware interface formally launched on a device in 2011 by Intel and Apple, a standard for connecting two devices together, and one which incorporates other standards like PCI Express (PCIe), DisplayPort, and (with the arrival of Thunderbolt 3) USB-C for the actual end connector.

As we’ve explained before, USB-C is a physical connector type, not a standard for shifting 1s and 0s (in fact it supports several of these standards, including USB and DisplayPort). These connectors are often developed in tandem with USB technology (such as USB 3.0), which is where confusion can quickly set in — and even more so when Thunderbolt 3 decides to make use of USB-C connections as well.

There's still confusion over how Thunderbolt 3 and USB-C fit together. (Image: Thunderbolt)

Actually, it’s a bit more complicated than that, because not all USB-C ports are Thunderbolt 3 ports, though all Thunderbolt 3 ports support USB-C (we know, we know). While any USB-C device will work with a Thunderbolt 3 port, not every Thunderbolt 3 device will work with a USB-C port that lacks the Thunderbolt 3 extras.

When it comes to the connector at least, Thunderbolt 3 is like USB-C enhanced. Top-end laptops like the MacBook Pro and the Dell XPS 13 use USB-C enhanced with Thunderbolt 3, so that they can support both Thunderbolt and USB peripherals — the XPS 13 actually has two standard USB-C ports and two USB-C-with-Thunderbolt-3 ports, which shows you just how complicated this can get for the average consumer.

You could plug any USB or Thunderbolt drive or display into one of the Thunderbolt 3 ports on your Dell XPS 13, and it would work; however, only drives and displays using USB would be guaranteed to work with the standard USB-C port without Thunderbolt 3, though some Thunderbolt devices would work, with certain limitations (slower speeds, for example). Hopefully that’s now crystal clear…

Image: Thunderbolt

This is all a rather long preamble but it’s important to cover it to properly understand Thunderbolt 4. Confusion and multiple standards aren’t really benefiting anyone at the moment, and so Thunderbolt 4 brings Thunderbolt and USB (both the connector type and the transfer protocol) closer than ever before. Long-winded explainers like the one we’ve just gone through should soon be consigned to history, hopefully.

USB 4 is borrowing a lot of standards from Thunderbolt 3, which means Thunderbolt 4 can borrow them back again and bring the two technologies even closer together. In fact, one of main improvements in Thunderbolt 4 is the adoption of USB 4 standards — the maximum bandwidth remains the same as it is in Thunderbird 3, 40Gbps.

Some of the minimum requirements are changing though, requirements that must be in place to earn the Thunderbolt 4 badge. That 40Gbps figure is now a minimum requirement rather than a potential maximum, so laptops can’t have different Thunderbolt ports with different speeds, and all Thunderbolt 4 ports must be able to power two 4K displays simultaneously (previously optional with Thunderbolt 3).

There's still confusion over how Thunderbolt 3 and USB-C fit together. (Image: Thunderbolt)

The theoretical limit for PCIe data transfer in particular is 32Gbps, while Thunderbolt 4 will also be able to maintain its maximum performance in cables up to two meters (six-and-a-half feet) in length. Thunderbolt 3, performance levels can change depending on the length of the cabling used.

A Thunderbolt 4 laptop must have at least one port capable of charging the device at 100W capacity, while Intel’s VT-d virtualization technology (which protects against direct memory attacks by isolating certain sections of the memory) must now be built in as a requirement; in the Thunderbolt 3 spec, it’s an option. Another Thunderbolt 4 requirement will be that laptops must be able to be charged by a Thunderbolt dock, and wake up from sleep when connected to one.

The USB-C connector is being retained of course, and Thunderbolt 4 products will work when plugged into Thunderbolt 3 ports, even if the performance isn’t quite what it would be with a fully Thunderbolt 4-compliant chain of ports, cables, and devices. In addition, Thunderbolt 4 docks will be capable of a few extra tricks in terms of how many different devices they can connect to in the same configuration.

Image: Thunderbolt

While the Thunderbolt 3 vs Thunderbolt 4 comparison doesn’t look all that exciting, wrapping in more seamless compatibility with USB and upping the minimum requirements justify the new number bump — it should finally take some of the confusion and guesswork out of using Thunderbolt.

Thunderbolt 4 compatibility will arrive on laptops with the introduction of the Tiger Lake processors from Intel, which are expected to hit the market in the very near future. If manufacturers want to, they should be able to incorporate Thunderbolt 4 into their devices before the end of the year. In other words, watch this space.

And where does this leave Macs and the move to Apple Silicon? As you’ll have noticed, the iPad Pro USB-C ports use USB rather than Thunderbolt, though Thunderbolt 3 is standard on the MacBook Pros and MacBook Air. Even as Apple moves away from Intel processors, it said in a statement given to The Verge and others that it remains committed to “the future of Thunderbolt” — which we’re hoping means Thunderbolt 4 as well as Thunderbolt 3.