USB 3, also known as USB 3.1 Gen 1, offers several improvements over previous USB standards:
- Higher Speed - USB 3 has a maximum throughput of up to 5 Gbit/s, nearly 10 times faster than USB 2
- Increased Power - USB 3 supports increased maximum power output up to 900mA, 50% more than USB 2
- Full Duplex Transmission - USB 3 allows simultaneous transmission of data in both directions
- Backward Compatibility - USB 3 is fully compatible with USB 2 devices
- New Connector - USB 3 introduces a new connector type with additional pins, but retains backwards compatibility
- Superspeed USB Branding - USB 3 is marketed under the SuperSpeed USB brand name
The major advantages of USB 3 over its predecessors are significantly faster data transfer speeds, increased power delivery, and full duplex data transmission while remaining backwards compatible.
On August 13, 2008, Intel announced the availability of the Extensible Host Controller Interface (xHCI) draft specification revision 0.9 in support of the USB 3.0 architecture, also known as SuperSpeed USB. The xHCI draft specification provides a standardized method for USB 3.0 host controllers to communicate with the USB 3.0 software stack. Interoperability among devices from multiple manufacturers is important for consumer adoption of SuperSpeed USB products. The Intel xHCI draft specification revision 0.9 supports compatibility among various implementations of USB devices and will make it easier to develop software support for the industry.
The specification describes the registers and data structures used to interface between system software and the hardware, and are developed to be compatible with the USB 3.0 specification being developed by the USB 3.0 Promoter Group. Intel plans to make available a revised xHCI 0.95 specification in the fourth quarter. The updated revision of the specification will also be released under RAND-Z licensing terms via an xHCI adopter's agreement.