USB 4.0!? Well, this can only get more confusing… again. Fortunately, USB4 (official name, but interchangeable) is set to become a truly universal protocol with an easy to understand lineup. Recently, the USB Implementers Forum (USB-IF) announced USB4 2.0 which launched the updated specification into the public market. The differences between USB 4.0 vs 3.0 are primarily speed and compatibility. There are a lot of other important updates as well, but USB 4.0 is an up to 80Gbps version of the USB interface that previously only went up to 20Gbps.
USB 4.0 vs 3.0 Updates
When the USB-IF was developing USB4, the goals they came up with were to address some problems with previous generations that had come about with industry changes, and focus on converging the USB-C connector ecosystem. In addition, they stated the desire to increase bandwidth to address some desires for PCI express tunneling. This particular go around at USB4, the USB-IF was able to gather partnering companies to help unify the project including HP, Microsoft, and connection competitors Intel and Apple.
At this point in technology history, the “universal connection world” is getting very complicated. For a while, USB was the premiere specification with USB-A rising to the top of universally compatible ports. Then, in collaboration with Apple, Intel designed the Thunderbolt connection. With the help of adopting the USB-C shaped connection, the Thunderbolt 3 interface became very prominent since it was faster than the USB-C shaped USB interface. That catches us up to where we are today. You can look at a USB-C port and not know if it’s USB or Thunderbolt. Of course, this causes compatibility issues when using peripheral devices.
Needless to say, compatiblity with Thunderbolt and previous generations of USB were the biggest goals of USB4. The public has become frustrated and confused at what peripheral devices are compatible with what host devices. Unifying the USB-C ecosystem was a major project. It’s important to note that USB4 is only on USB-C. But, with the help of the Thunderbolt creators Intel and Apple, the USB-IF was able to develop USB4 to work across platforms! However, the frustrating part is that the USB-IF doesn’t require all compatibility options to be present on official USB4 devices. This chart lays out what USB4 is compatible with and what is required to claim USB4.
|USB 1.0 or 2.0||X||X||X|
|USB4 20 Gbit/s||X||X||Not Required|
|USB4 40 Gbit/s||Not Required||X||Not Required|
|Tunneled USB 3.2 10Gbit/s||X||X||X|
|Tunneled USB 3.2 20Gbit/s||Not Required||Not Required||Not Required|
|Tunneled Display Port||X||X||Not Required|
|Tunneled PCIe||Not Required||X||Not Required|
So, for example, if a laptop were to be USB4 certified, it would only have to have backwards compatibility with USB 1 and 2, USB4 20Gbit/s, Tunneled USB3.2 10Gbit/s, and Tunneled Display Port. Although the newfound compatibility is amazing news for the community and the technology world as a whole, the optional components of USB4 opens the doors to more incompatibility, since you don’t have to have all of the compatible boxes checked off to qualify. You could have a USB4 certified computer and attempt to use a 40Gbit/s peripheral but never see those speeds because that is optional on host devices. Unfortunately, this variation reintroduces incompatibility into a platform that was designed to unify the environment.
With any new technology, there’s growth in regular areas of performance. USB 4.0 is no different, boasting up to 15GB/s. This is achieved through a triple channel configuration where each channel can deliver 5GB/s. For perspective, a standard USB 3.2 Gen 2×2 exteranal SSD transfers at 2GB/s. This makes USB4 ideal for many cases of use for large volume data transfers that require incredible speeds. The chart below lays out the speeds by classification with conversions.
|USB4 Generation Name||Max Speed in GB/s||Max Speed in Gbit/s|
|USB4 Gen 2×1||1.25 GB/s||10 Gbit/s|
|USB4 Gen 2×2||2.5 GB/s||20 Gbit/s|
|USB4 Gen 3×1||2.5 GB/s||20 Gbit/s|
|USB4 Gen 3×2||5 GB/s||40 Gbit/s|
|USB Gen 4 Single||5 GB/s||40 Gbit/s|
|USB Gen 4 Dual||10 GB/s||80 Gbit/s|
|USB Gen 4 Triple||15 GB/s||120 Gbit/s|
New Features of USB4
Now, the best part, taking the newfound compatibility and super fast speeds of USB 4.0 vs 3.0, to incredible new features and opportunities. The most exciting is the PCIe tunneling. In case you don’t know, inside your computer are PCIe slots. Otherwise known as PCI express, these are super fast connections that your motherboard uses to interface with expansion cards that need virtually zero latency and instant data transfer to your computer’s main bus. There are many kinds of PCIe, and USB4 is now fast enough to compete with some of the slower versions! That’s incredible news for people with laptops that want to use desktop PCIe cards with their system. The options are beginning to be developed: external desktop graphics cards, sound cards, NVME M.2 SSDs, and more! Things you could never have with a mobile laptop workstation are now available with expandable PCIe tunneling from USB4.
The problem with USB 4.0 vs 3.0 names
Confusion seems to be a byproduct of every new name that the USB-IF develops. However, unlike the previous naming schemes, the last generation names are not lumped into the new generation names. Here’s a chart to help you identify where the older products fit into the new USB4 naming format.
|USB4 Generation Name||Marketing Name||Legacy Name|
|USB 3.2 Gen 1×1||SuperSpeed USB 5Gbps||USB 3.0, USB 3.1 Gen 1|
|USB 3.2 Gen 1×2|
|USB 3.2 Gen 2×1||SuperSpeed USB 10Gbps||USB 3.1 Gen 2|
|USB 3.2 Gen 2×2||SuperSpeed USB 20Gbps|
|USB4 Gen 2×1|
|USB4 Gen 2×2||USB4 20Gbps|
|USB4 Gen 3×1|
|USB4 Gen 3×2||USB4 40Gbps|
|USB Gen 4 Symmetric||USB4 80Gbps|
|USB Gen 4 Asymmetric||USB4 80Gbps|
USB 4.0 vs 3.0 Wrap-Up
There are certainly some mixed results. I think overall this is going to be huge for the technology industry. Being able to use Thunderbolt 3/4 devices with USB4 compatible devices opens the doors to so many cross platform possibilities. The key thing to keep an eye out for is what manufacturers opt in to on the optional qualifications chart. Because the USB-IF is keeping around the USB 3.2 names with USB4, it will be harder to get scammed with a slower speed product. However, this won’t stop companies from doing what they can to sell you a product that is less than what a full USB4 feature-packed device could be. Refer back to this article as a resource in your USB4 product journey.
Linus Tech Tips made a very helpful video to try and clarify some of the optional features and even tested the forwards and backwards compatibility of USB4 and Thunderbolt. You can find that video here.