When you want more performance from your USB cables and ports, the only way to get significant gains is to upgrade your hardware. New cables, new ports… new motherboard, new laptop. It gets expensive, fast.
That is, unless you’re using USB4 v2, which, in the right circumstances, can double its speed without much effort at all.
How USB4 v2 doubles its speed without a new cable
You might be leaving performance on the table
When the USB Implementers Forum (USB-IF) published the USB4 Version 2.0 specification in October 2022, it introduced support for data transfer speeds of up to 80Gbps.
That’s double the 40Gbps maximum bandwidth supported by the original USB4 specification, but, interestingly, USB4 Version 2.0 can achieve this improvement using existing 40Gbps passive USB-C cables, provided the connected hardware supports the newer standard.
Normally, doubling the data speeds needs a big upgrade to the hardware, but this speed upgrade changes how compatible hardware transmits data rather than requiring an entirely new physical connection.
It all comes down to how information is encoded between two different systems, with USB4 v2 using a new architecture compared to the old version.
In most cases, data travels down a cable as a stream of electrical signals, effectively working like a light switch, in that it’s on or off, and it works. It’s called non-return-to-zero (NRZ), where each signal carries about 1 bit.
USB4 v2 introduces a third position using a technique known as Pulse Amplitude Modulation, 3-level (PAM3), which allows three voltage levels instead of two. That allows more data per signal, increasing from 1 bit to a theoretical ceiling of 1.58 bits, but all using the same cables as before. It’s basically doing more with the same hardware and wires using some behind-the-scenes upgrades to deliver better speeds.
That difference in Pulse Amplitude Modulation is what enables a 40Gbps USB4 cable to magically jump to 80Gbps.
That sounds great, but not every cable can pull off the magic
Unfortunately, your cable drawer is still full of duds
Now, I’d love to tell you that every USB4 cable in your house is capable of this wondrous feat, but that’s simply not the case. The range of cables that can actually pull this off isn’t as broad as you may think, and is confined to USB4 cables. You can’t upgrade a USB 2.0 cable to suddenly support 80Gbps; that’s not how it works. It’s not how anything works, for that matter.
First, you need a passive USB4 cable specifically built for 40Gbps. This definition is important because a variety of USB4 cables exist, and the one that came bundled with another device may not be up for the task. That’s because sometimes, knowing that a device doesn’t really need the full 40Gbps that USB4 can deliver, manufacturers ship lower-quality cables only capable of 20Gbps.
If you already own a suitable 40Gbps passive USB-C cable, it may be capable of supporting the higher bandwidth available through USB4 Version 2.0. The connected devices must also support the newer standard, however, and the cable must meet the relevant requirements. Simply connecting an older USB4 device to a newer one won’t magically double its performance.
There is another limit to be aware of: cable length. Passive cables are typically shorter to allow the signal to transmit properly. If your passive cable is longer than one meter, it’s unlikely to be able to hit the 80Gbps mark as the signal becomes too weak.
How to check the USB4 cables you already own
Cables don’t scream capabilities
So, what you’re looking for is a USB4 cable marked for 40Gbps under one meter in length. If you’ve already specifically bought one, you can give that a try.
Otherwise, to find out, you need a USB testing tool and a couple of hours to go through all your cables. Time-consuming, but at least you know where you stand.
There is also the option of using software like WhatCable, a tool designed to read e-marker data to identify cables and their capabilities. That said, given we’re looking for passive 40Gbps cables, they won’t contain an active e-marker, so that could also be a bust.
Head back to Amazon, or other retailers where you bought the cable to see the full specs, and work from there. Alternatively, pick up a USB-C Tester Power Meter for around $10-15, and get your sticky label machine out.
Extra bandwidth is great, but I wouldn’t rely on this technique
On the one hand, this shows that there is performance left on the table that you can tap into with the right cable combination. On the other, it could mean several hours plugging in cables to your devices and figuring out which one delivers the goods.
My techy-man inner-vibe, with a box full of cables, yearns for the testing. My busy work and life schedule pretty much says get online and just buy a cable that does the job to begin with. Still, it’s an option in a pinch!