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USB 3.0 (renamed to ''USB 3.1 Gen 1'' in 2015) is the third major version of the Universal Serial Bus (USB) standard for interfacing computers and electronic devices. Among other improvements, USB 3.0 adds the new transfer mode ''SuperSpeed'' (SS) that can transfer data at up to 5 Gbit/s (625 MB/s), which is about ten times faster than the USB 2.0 standard. USB 3.0 connectors are usually distinguished from their USB 2.0 counterparts by blue color-coding of the receptacles and plugs, and the initials ''SS''. A successor standard, USB 3.1 (renamed to ''USB 3.1 Gen 2'' in 2015〔), was released in July 2013 with the new transfer mode ''SuperSpeed+'' that can transfer data at up to 10 Gbit/s (1.25 GB/s, twice the rate of USB 3.0), bringing its theoretical maximum speed on par with the first version of the Thunderbolt interface. == Overview == The USB 3.0 specification is similar to USB 2.0 but with many improvements and an alternative implementation. Earlier USB concepts like endpoints and 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 added 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 instead of one-way communication, USB 3.0 uses two unidirectional data paths: one to receive data and the other to transmit * Power management U0 through U3 link power management states are defined * Improved bus utilization a new feature is added (using packets NRDY and ERDY) to let a device asynchronously notify the host of its readiness (no need for polling) * Support to rotating media 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, which is about ten times faster than USB 2.0 (480 Mbit/s) before taking into account that USB 3.0 is full duplex whereas USB 2.0 is half duplex, giving USB 3.0 the potential total bandwidth if utilized both ways to twenty times that of USB 2.0. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「USB 3.0」の詳細全文を読む スポンサード リンク
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