USB 3.0, released in November 2008, is the third major version of the Universal Serial Bus (USB) standard for interfacing computers and electronic devices. The USB 3.0 specification defined a new architecture and protocol, named SuperSpeed, which included a new lane for a new signal coding scheme (8b/10b symbols, 5 Gbps; also known later as Gen 1) providing full-duplex data transfers that physically required five additional wires and pins, while preserving the USB 2.0 architecture and protocols and therefore keeping the original four pins and wires for the USB 2.0 backward-compatibility, resulting in nine wires in total and nine or ten pins at connector interfaces (ID-pin is not wired). The new transfer rate, marketed as SuperSpeed USB (SS), can transfer signals at up to 5 Gbit/s with nominal data rate of 500 MB/s after encoding overhead, which is about 10 times faster than High-Speed (maximum for USB 2.0 standard). USB 3.0 Type-A and B connectors are usually blue, to distinguish them from USB 2.0 connectors, as recommended by the specification. and by the initials SS.
USB 3.1, released in July 2013, is the successor specification that fully replaces the USB 3.0 specification. USB 3.1 preserves the existing SuperSpeed operation mode (8b/10b symbols, 5 Gbps), giving it the new label USB 3.1 Gen 1. USB 3.1 introduced an Enhanced SuperSpeed System to the SuperSpeed architecture and protocol, and providing a new coding schema (128b/132b symbols) and protocol named SuperSpeedPlus (sometimes marketed as SuperSpeed+ or SS+) while defining a new transfer mode called USB 3.1 Gen 2 with a signal speed of up to 10 Gbit/s and a nominal data rate of 1212 MB/s over existing Type-A, Type-B, and USB-C connections, more than twice the rate of USB 3.0 (aka Gen 1).. Backward-compatibility is still given by the parallel USB 2.0 implementation. USB 3.1 Gen 2 Type-A and Type-B connectors and plugs are usually teal-colored.
USB 3.2, released in September 2017, fully replaces the USB 3.1 specification. The USB 3.2 specification added a second lane to the Enhanced SuperSpeed System besides other enhancements, so that SuperSpeedPlus USB implements the Gen 2x1 (aka USB 3.1 Gen 2), and the two new Gen 1x2 and Gen 2x2 operation modes while operating on two lanes. The SuperSpeed architecture and protocol (aka SuperSpeed USB) still implements the one-lane Gen 1x1 operation mode (aka USB 3.1 Gen 1). Therefore, two-lane operations, namely USB 3.2 Gen 1x2 (10 Gbit/s with nominal data rate of 1 GB/s after encoding overhead) and USB 3.2 Gen 2x2 (20 Gbit/s, 2.422 GB/s), are only possible with Full-Featured USB Type-C Fabrics (24 pins). As of 2023, USB 3.2 Gen 1x2 and Gen 2x2 are not implemented on many products yet. On the other hand, USB 3.2 Gen 1(x1) (5 Gbit/s) and Gen 2(x1) (10 Gbit/s) implementations are quite common now for some years. Again, backward-compatibility is given by the parallel USB 2.0 implementation.
Overview
The USB 3.0 specification is similar to USB 2.0, but with many improvements and an alternative implementation. Earlier USB concepts such as endpoints and the four transfer types (bulk, control, isochronous and interrupt) are preserved but the protocol and electrical interface are different. The specification defines a physically separate channel to carry USB 3.0 traffic. The changes in this specification make improvements in the following areas: Transfer speed USB 3.0 adds a new transfer type called SuperSpeed or SS, 5 Gbit/s (electrically, it is more similar to PCI Express 2.0 and SATA than USB 2.0) Increased bandwidth USB 3.0 uses two unidirectional data paths instead of only one: one to receive data and the other to transmit Power management U0 to U3 link power management states are defined Improved bus use a new feature is added (using packets NRDY and ERDY) to let a device asynchronously notify the host of its readiness, with no need for polling Support for rotating media the bulk protocol is updated with a new feature called Stream Protocol that allows a large number of logical streams within an Endpoint
USB 3.0 has transmission speeds of up to 5 Gbit/s or 5000 Mbit/s, about ten times faster than USB 2.0 (0.48 Gbit/s) even without considering that USB 3.0 is full duplex whereas USB 2.0 is half duplex. This gives USB 3.0 a potential total bidirectional bandwidth twenty times greater than USB 2.0. Considering flow control, packet framing and protocol overhead, applications can expect 450 MB/s of bandwidth.