USB 3.0

The USB 3.0 Promoter Group announced on November 17, 2008, that version 3.0 of the specification had been completed and was transitioned to the USB Implementers Forum (USB-IF), the managing body of USB specifications. This move effectively opened the specification to hardware developers for implementation in future products. The first certified USB 3.0 consumer products were announced January 5, 2010, at the Las Vegas Consumer Electronics Show (CES), including two motherboards by ASUS and Gigabyte Technology.

Features
A new major feature is the "SuperSpeed" bus, which provides a fourth transfer mode at 5.0 Gbit/s. The raw throughput is 4 Gbit/s, and the specification considers it reasonable to achieve 3.2 Gbit/s (0.4 GByte/s or 400 MByte/s), or more, after protocol overhead.

When operating in SuperSpeed mode, full-duplex signaling occurs over two differential pairs separate from the non-SuperSpeed differential pair. This results in USB 3.0 cables containing two wires for power and ground, two wires for non-SuperSpeed data, and four wires for SuperSpeed data, and a shield that was not required in previous specifications.

To accommodate the additional pins for SuperSpeed mode, the physical form factors for USB 3.0 plugs and receptacles have been modified from those used in previous versions. Standard-A cables have extended heads where the SuperSpeed connectors extend beyond and slightly above the legacy connectors. Similarly, the Standard-A receptacle is deeper to accept these new connectors. On the other end, the SuperSpeed Standard-B connectors are placed on top of the existing form factor. A legacy standard A-to-B cable will work as designed and will never contact any of the SuperSpeed connectors, ensuring backward compatibility. SuperSpeed standard A plugs will fit legacy A receptacles, but SuperSpeed standard B plugs will not fit into legacy standard B receptacles, so a new cable can be used to connect a new device to an old host, but not to connect a new host to an old device; for that, a legacy standard A-to-B cable will be required.

SuperSpeed establishes a communications pipe between the host and each device, in a host-directed protocol. In contrast, USB 2.0 broadcasts packet traffic to all devices.

USB 3.0 extends the bulk transfer type in SuperSpeed with Streams. This extension allows a host and device to create and transfer multiple streams of data through a single bulk pipe.

New power management features include support of idle, sleep and suspend states, as well as link-, device-, and function-level power management.

The bus power spec has been increased so that a unit load is 150 mA (+50% over minimum using USB 2.0). An unconfigured device can still draw only one unit load, but a configured device can draw up to six unit loads (900 mA, an 80% increase over USB 2.0 at a registered maximum of 500 mA). Minimum device operating voltage is dropped from 4.4 V to 4 V.

USB 3.0 does not define cable assembly lengths, except that it can be of any length as long as it meets all the requirements defined in the specification. Although electronicdesign.com estimated cables will be limited to 3 m at SuperSpeed, cables which support SuperSpeed are already available up to 5 m in length.

The technology is similar to a single channel ("1×") of PCI Express 2.0 (5 Gbit/s). It uses 8B/10B encoding, linear feedback shift register (LFSR) scrambling for data and spread spectrum. It forces receivers to use low frequency periodic signaling (LFPS), dynamic equalization, and training sequences to ensure fast signal locking.

Availability
Consumer products became available in January 2010. To ensure compatibility between motherboards and peripherals, all USB-certified devices must be approved by the USB Implementers Forum (USB-IF). At least one complete end-to-end test system for USB 3.0 designers is on the market.

On January 5, 2010, USB-IF announced the first two certified USB 3.0 motherboards, one by Asus and one by Gigabyte. Previous announcements included Gigabyte's October 2009 list of seven P55 chipset USB 3.0 motherboards, and an ASUS motherboard that was cancelled before production.

Commercial controllers are expected to enter into volume production in the first quarter of 2010. On September 24, 2009 Freecom announced a USB 3.0 external hard drive. On January 4, 2010, Seagate announced a small portable HDD with PC Card targeted for laptops (or desktop with PC Card slot addition) at the CES in Las Vegas.

Drivers are under development for Windows 7, but support was not included with the initial release of the operating system. The Linux kernel has supported USB 3.0 since version 2.6.31, which was released in September 2009.

Intel will not support USB 3.0 until 2011, which will slow down mainstream adoption. These delays may be due to problems in the CMOS manufacturing process, a focus to advance the Nehalem platform, a wait to mature all the 3.0 connections standards (USB3, PCIe3, SATA3.0) before developing a new chip set, or a tactic by Intel to boost its upcoming Light Peak interface. Current AMD roadmaps indicate that the new southbridges released in the beginning of 2010 will not support USB 3.0. Market researcher In-Stat predicts a relevant market share of USB 3.0 not until 2011.
Source By Wikipedia | usb.org