to bring them in line with other USB specifications, where the nominal bit rate matches the raw bit rate. USB4 also added support for USB3 tunnels and use of the USB2 wires for improved backward compatibility with previous USB standards and to allow for simpler USB4 devices without support for PCIe. USB4 also added support for hub topologies compared to Thunderbolt's previous restriction to daisy-chaining topology.

In July 2020 Intel announced Thunderbolt 4 as an implementation of USB4 40 Gbit/s with additional requirements, such as mandatory