USB4 vs. USB4 2.0

USB4, released August 2019, is built on Intel's Thunderbolt 3 protocol, donated to USB-IF as the new foundation -- up to 40 Gbit/s, a mandatory USB-C connector, and tunneling that lets a single port carry USB, DisplayPort, and PCIe traffic at once. Thunderbolt 3 compatibility is required; Thunderbolt 4 compatibility is optional for device makers.

USB4 2.0, released September 2022, doubles USB4's ceiling to 80 Gbit/s symmetric -- or an asymmetric 120/40 Gbit/s split favoring one direction for high-bandwidth uses like external displays. It requires new cables explicitly rated for the higher speed; existing USB4 v1 cables aren't guaranteed to reach it.