The USB 3.0 version carries the designation SuperSpeed. After USB 1.x, which could transmit 1.5 Mbit/s as a low-speed interface, USB 1.1 with "Full Speed" and 12 Mbit/s transmission rate and USB 2.0, designated as "High Speed", with 480 Mbit/s, USB 3.0 follows as SuperSpeed with 5 Gbit/s in full duplex and thus a tenfold increase in data rate compared to USB 2.0. The next highest speed class is USB 3.1, SuperSpeed+ with 10 Gbit/s. It was introduced in 2013.
The specifications for USB 3.0 presented in 2008 by the USB 3.0 promoter group cover the mechanical, electrical and logical aspects. It is a new bus concept with its own USB connectors and USB cables that is backward compatible with USB 2.0. USB 3.0 will meet the demands of modern hard disk drives and solid-state drives( SSD), as USB 2.0's transfer rates of 30 MB/s no longer meet requirements.
A SuperSpeed configuration can be viewed as a star distribution, where distribution points are called hubs, virtual channels are called pipes, devices are called nodes, and subscribers are called functions. In such a configuration, the connections are implemented in a star configuration via USB hubs as point-to-point connections between the different hierarchy levels. The data is transferred via the USB hub only to the addressed peripheral device. This allows the peripherals to operate in different power saving modes, which helps to save energy.
As for the transmission protocol, isochronous transmission uses a portion of the available bandwidth cyclically for real-time transmissions ofvideo and audio. However, this requires buffer memories to cache the information. Other data is transmitted to the peripheral devices in asynchronous mode.
The SuperSpeed connector differs from the classic USB connector. It has nine plug contacts and uses a special USB 3.0 cable. The plug contacts 1 to 4 are on the lower plug side and correspond in position and arrangement to the plug contacts of USB 2.0, which explains the backward compatibility. The other five plug contacts 5 to 9 are located opposite each other on the upper connector side and are for the opposite- phase SuperSpeed data lines for transmitter and receiver. USB 3.0 supports USB Battery Charging( USB-BC) and USB Power Delivery( USB-PD) with an output of 4.5 W. With USB3 Vision, an interface for industrial image processing has been standardized.
Thunderbolt, which features a data rate of 10 Gbit/s, is an interesting alternative to USB 3.0 and other HS interfaces.