We all know that the USB-C protocol is confusing and far from the one size fits all approach that was envisaged in its early days. The USB-C ports and cables are capable of supporting a wide variety of speeds, power capabilities, and other features, which depends on the specification used.
Today, USB-C is capable of supporting a range of data transmission rates, from 0.48Gbps (USB 2.0) to 40Gbps (USB4, Thunderbolt 3, and Thunderbolt 4). The USB4 Version 2.0 spec was launched recently by the USB Implementers Forum (USB-IF), which means the situation is about to get worse. It also includes the option to transmit data at up to 120Gbps and optionally enable 80Gbps bi-directional bandwidth.
A new physical layer architecture (PHY) based on PAM-3 signal encoding, announced by the USB-IF in September, will enable data transfer rates of up to 80Gbps in either direction (40Gbps per lane, four lanes total). To be fair, Intel also demonstrated Thunderbolt at 80Gbps, but the company hasn’t yet published an official spec.
A great improvement over the original USB4 specification, which included optional capability for 40Gbps operation, is provided by USB4 Version 2.0. To know what kind of performance you’re receiving, just be sure to look at the specifications list. When USB4 Version 2.0 items are released, USB-C passive cables that now run at 40Gbps will be able to reach 80Gbps; however, another cable will need to be purchased by you in case you want a longer, active 80Gbps transfer connection.
A USB4 Version 2.0 port that may operate at 120 Gbps typically transmits and receives data at 80 Gbps. When a device attaches to the port, “The preferred mode of operation will be identified by the USB4 discovery process controlled by system software. The port would initially establish a connection at 80Gbps before switching to 120Gbps operation” CEO and Board Chair of the USB-IF, Brad Saunders, explained to Ars Technica.
However, the most likely application will see data being delivered from a computer to a high-performance monitor at 120Gbps, with a 40Gbps lane left available for sending data to the system. The new specification permits both transmitting and receiving data at 120Gbps.
