Not All Cables Are Made the Same

This brings us to the next subject—cables. This is a very complex topic, but there is at least some good news here. For starters, the USB-IF seems to have become stricter when it comes to the labelling of certified cables, and even the base cables now have to be capable of 20 Gbps of data over four data pairs, and at least 60 W of power. There are separate logos for 40 Gbps cables as well as 240 W power delivery. As there's minimal difference between the 100 W and 240 W cables, it appears the USB-IF decided against a 100 W certification level.



Something that is less obvious and something we were unaware of until we started asking around about USB4 is that you shouldn't throw away your old USB-C cables as they might actually work better with USB4. This sounds utterly mad at first—why would an older cable work better with a new standard? Well, it's because the USB-IF has changed what is known as the link or loss budget for USB-C cables. The table below compares the signal loss budget of various USB standards. The "dB" value is how much of the original signal strength is lost. As you can see, the loss budget has been shifted. On the host and device side, there's now much less loss allowed, but the cables can have much bigger losses. This means that cables that have been edge cases previously should now work just fine at 10 Gbps speeds, and some 20 Gbps capable cables might be able to work at 40 Gbps speeds.


The dB in the graphic above refers to the loss budget, where a higher value for the cable and a lower value for the host and device is better than a higher value for the host and device and a lower value for the cable.

We should point out that cable lengths will play a big role as well, as longer cables have bigger signal loss. All things considered equal, USB4 will not require new cables for data usage if you already own quality cables, except possibly for 40 Gbps data transfers. Thunderbolt cables with USB Type-C connectors are also compatible with USB4.

Another minor and unnoticeable change is a modification to the USB-C plug and receptacle, as in rare cases there could be a short. This change was implemented alongside USB PD 3.1 and EPR mode, which means all USB4 cables should adhere to this change.