While specifications won’t be finalized until later this year, USB 4 should support speeds of 40 Gbps. The USB-IF is using Thunderbolt 3 as the foundation for USB 4.
Intel originally developed the Thunderbolt interface with Apple back in 2011. It was supposed to be a faster and more versatile interface that supports multiple protocols. For instance, you can use Thunderbolt cables and devices to connect displays and hard drives. You can daisy-chain your peripherals, which can be useful for external graphics cards, for instance.
With Thunderbolt 3, Intel added USB 3.1 Gen 2 support, which means that you can plug a device to a Thunderbolt port. And Intel adopted the USB-C port. In other words, Thunderbolt ports became USB ports with Thunderbolt capabilities on top. It means that any USB device can be used with a Thunderbolt port. If you’re using a MacBook Pro, you’ve probably taken advantage of that feature.
But USB devices plugged into Thunderbolt ports don’t magically become Thunderbolt devices. If you plug an external USB 3.0 hard drive in a Thunderbolt port, you’re limited to USB 3.0 speeds.
Even though Thunderbolt is technically superior, it hasn’t been as popular as USB devices. Device manufacturers had to pay royalty fees to Intel (Correction: Thunderbolt 3 has always been royalty-free, but specifications weren’t public). Making a Thunderbolt device is also more expensive in general.
A couple of years ago, Intel announced that it would make Thunderbolt available to everyone without any royalty fee. So the USB-IF is taking advantage of that by integrating Thunderbolt 3 specifications into USB 4.
USB 4.0 will support charging speeds of 100W of power, transfer speeds of 40 Gbps and enough video bandwidth for two 4K displays or one 5K display. USB 4 should also be backward-compatible with USB 3.x, 2.x and 1.x devices.
If you have a USB 3.x cable with Type-C connectors, you may have to upgrade to USB 4 cables. But Thunderbolt 3 should work fine, as they’re essentially the same thing as USB 4 cables. I hope there will be a way to distinguish USB 3.x ports from USB 4 ports though.
Intel won’t drop the Thunderbolt name altogether. Thunderbolt devices are certified by Intel, while you don’t need any certification to release a USB device.
USB 4 sounds like a great way to start from a clean slate. One port and one cable type to rule them all. But let’s hope manufacturers follow the official specifications and don’t try to cut corners.