Both USB 3.1 and USB 3.2 were introduced to increase bandwidth, and the design goals of USB4 remain unchanged. However, the release of this specification is also to integrate the USB Type-C ecology and reduce the confusion of end users.
Although the new USB4 standard introduces a new underlying protocol, it is still compatible with the existing USB3.2, USB2.0 and Thunderbolt 3. USB4 will adopt a dual-channel dual-simplex architecture, which doubles the transmission bandwidth of Type-C, with a transmission rate of at least 20Gbps and optional 40Gbps. The maximum transmission rate is twice that of the previous generation USB 3.2. For certified interfaces and cables Two different logos will also be provided. For 40Gbps USB4, the encoding method is still 128b/132b used by USB 3.2, while 20Gbps will use 64b/66b. A USB4 source provides at least 7.5W of power (5V, 1.5A) per port.
In addition, USB4 adds tunnel support to support PCie and DisplayPort1.4a, thereby achieving multi-protocol compatibility on a single physical interface. Brad Saunders pointed out that most computers equipped with USB4 will be compatible with Thunderbolt 3, but for mobile phone manufacturers, this support should not be added. As for software support, it is known that the Linux 5.6 system already supports USB4, and the USB4 driver for Microsoft Windows is said to be still under development.
Cypress announced in March 2020 the Type-C controllers for next-generation desktop and mobile computers, EZ-PD CCG6DF and EZ-PD CCG6SF. Both controllers are single-chip solutions and are compatible with USB 3.2/4.
CCG6DF/CCG6SF logic block diagram / Infineon-Cypress
CCG6DF/CCG6SF supports dual role ports (DRP) and will fully support PD3.0 specifications. The program includes 64KB of flash storage and 96KB of ROM storage, and supports fail-safe startup and firmware upgrades.