The Universal Serial Bus 3.0 Specification Revision 1.0 was released in November 2008, with the first USB 3.0 device-controller hardware expected to follow about a year later. Windows will likely support USB 3.0 sometime after the release of Windows 7, the successor to Windows Vista.
USB 3.0 defines a new dual-bus architecture with two physical buses that operate in parallel. USB 3.0 provides a pair of wires for USB 2.0 traffic and additional wires to support the new SuperSpeed bus at 5 Gbps. SuperSpeed offers a more than 10× increase over USB 2.0’s high speed. Plus, unlike USB 2.0, SuperSpeed has a pair of wires for each direction and can transfer data in both directions at the same time.
USB 3.0 also increases the amount of bus current devices can draw and defines protocols for more aggressive power saving and more efficient transfers.USB 3.0 is backwards compatible with USB 2.0. USB 3.0 hosts and hubs support all four speeds. USB 2.0 cables fit USB 3.0 receptacles.USB 3.0 supplements, but doesn’t replace, USB 2.0. Low, full, and high-speed devices continue to comply with USB 2.0 and can’t take advantage of USB 3.0’s features such as higher bus-current limits and larger data packets.
As USB became the interface of choice for all kinds of peripherals, developers began to ask for a way for USB peripherals to access other USB devices. For example, a user might want to attach a printer to a camera or a keyboard to a PDA. The On-The-Go (OTG) Supplement to the USB 2.0 Specification defines a limited-capability host function that devices can implement to enable communicating with USB peripherals.
Tags: device-controller, USB 3.0, Windows 7, Windows Vista
