The Super-Speed USB logo
|Manufacturer||USB 3.0 Promoter Group (Hewlett-Packard, Intel, Microsoft, NEC, ST-Ericsson, and Texas Instruments)|
|Superseded||USB 2.0 Hi-Speed|
|Superseded by||USB 3.1 (July 2013)|
|Width||12 mm (A plug), 8 mm (B plug), 12.2 mm (Micro-A & Micro-B plugs)|
|Height||4.5 mm (A plug), 10.44 mm (B plug), 1.8 mm (Micro-A & Micro-B plugs)|
|Max. current||900 mA|
USB 3.0 is the second major revision of the Universal Serial Bus (USB) standard for computer connectivity. First introduced in 2008, USB 3.0 adds a new transfer mode called "SuperSpeed," (distinguishable from USB 2.0 by either the blue colour of the port or the initials SS) capable of transferring data at up to 5Gbit/s—more than ten times as fast as the 480 Mbit/s top speed of USB 2.0.
- 1 Implementation differences compared to USB 2.0
- 2 Availability
- 3 Speed issues
- 4 Radio frequency interference
- 5 Connectors
- 6 See also
- 7 References
- 8 External links
Implementation differences compared to USB 2.0
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 Super Speed or SS – 5 Gbit/s (electrically it is more similar to PCIe Gen2 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 10 times as fast as 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 20 times that of USB 2.0.
Architecture and features
In USB 3.0, dual-bus architecture is used to allow both USB 2.0 (Full Speed, Low Speed, or High Speed) and USB 3.0 (Super Speed) operations to take place simultaneously, thus providing backward compatibility. Connections are such that they also permit forward compatibility, that is, running USB 3.0 devices on USB 2.0 ports. The structural topology is the same, consisting of a tiered star topology with a root hub at level 0 and hubs at lower levels to provide bus connectivity to devices.
Data transfer and synchronization
The SuperSpeed transaction is initiated by the host making a request followed by a response from the device. The device either accepts the request or rejects it. If accepted then device sends data or accepts data from the host. If the endpoint is halted, the device shall respond with a STALL handshake. If there is lack of buffer space or data, it responds with a Not Ready (NRDY) signal to tell the host that it is not able to process the request. When the device is ready then, it will send an Endpoint Ready (ERDY) to the host which will then reschedule the transaction.
The use of unicasting and the limited multicasting of packets, combined with asynchronous notifications, enables links that are not actively passing packets to be put into reduced power states, allowing for better power management.
The "SuperSpeed" bus provides for a transfer mode at a nominal rate of 5.0 Gbit/s, in addition to the three existing transfer modes. Accounting for encoding overhead, the raw data throughput is 4 Gbit/s, and the specification considers it reasonable to achieve 3.2 Gbit/s (0.4 GB/s or 400 MB/s) or more in practice.
All data is sent as a stream of eight bits (one byte segments) which are scrambled and then converted into a 10-bit format. This helps to reduce electromagnetic interference (EMI). The inverse process is carried out at the receiving end. Scrambling is implemented using a free running linear feedback shift register (LFSR). The LFSR is reset whenever a COM symbol is sent or received.
Unlike previous standards, the USB 3.0 standard does not directly specify a maximum cable length, requiring only that all cables meet an electrical specification: for copper cabling with AWG 26 wires the maximum practical length is 3 meters (9.8 ft).
The USB 3.0 Promoter Group announced on 17 November 2008 that the specification of version 3.0 had been completed and had made the transition 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 USB 3.0 consumer products were announced and shipped by Buffalo Technology in November 2009, while 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.
Manufacturers of USB 3.0 host controllers include, but are not limited to, Renesas Electronics, Fresco Logic, ASMedia Technology, Etron, VIA Technologies, Texas Instruments, NEC and Nvidia. As of November 2010, Renesas and Fresco Logic have passed USB-IF certification. Motherboards for Intel's Sandy Bridge processors have been seen with Asmedia and Etron host controllers as well. On October 28, 2010, Hewlett-Packard released the HP Envy 17 3D featuring a Renesas USB 3.0 host controller several months before some of their competitors. AMD worked with Renesas to add its USB 3.0 implementation into its chipsets for its 2011 platforms.[dated info] At CES2011, Toshiba unveiled a laptop called "Toshiba Qosmio X500" that included USB 3.0 and Bluetooth 3.0, and Sony released a new series of Sony VAIO laptops that will include USB 3.0. As of April 2011, the Inspiron and Dell XPS series are available with USB 3.0 ports, and, as of May 2012, the Dell Latitude laptop series, yet the USB root hosts fail to work at super-speed under Windows 8. On June 11, 2012, Apple announced new MacBook Airs and MacBook Pro with USB 3.0.
Adding to existing equipment
In laptop computers that lack USB 3.0 ports but have an ExpressCard slot, USB 3.0 ports can be added by using an ExpressCard-to-USB 3.0 adapter. Although the ExpressCard port itself is powered from a 3.3 V line, the connector also has a USB 2.0 port available to it (some express cards actually use the USB 2.0 interface rather than the true express card port). However, this USB 2.0 port is only capable of supplying the power for one USB 3.0 port. Where multiple ports are provided on the express card, additional power will need to be provided.
Additional power for multiple ports on a laptop PC may be derived in the following ways:
- Some ExpressCard-to-USB 3.0 adapters may connect by a cable to an additional USB 2.0 port on the computer, which supplies additional power.
- The ExpressCard may have a socket for an external power supply.
- If the external device has an appropriate connector, it can be powered by an external power supply.
- USB 3.0 port provided by an ExpressCard-to-USB 3.0 adapter may be connected to a separately-powered USB 3.0 hub, with external devices connected to that USB 3.0 hub.
On the motherboards of desktop PCs which have PCI Express (PCIe) slots (or the older PCI standard), USB 3.0 support can be added as a PCI Express expansion card. In addition to an empty PCIe slot on the motherboard, many "PCI Express to USB 3.0" expansion cards must be connected to a power supply such as a Molex adapter or external power supply, in order to power many USB 3.0 devices such as mobile phones, or external hard drives that have no power source other than USB; as of 2011, this is often used to supply two (2) to four (4) USB 3.0 ports with the full 0.9 A (4.5 W) of power that each USB 3.0 port is capable of (whilst also transmitting data), whereas the PCI Express slot itself cannot supply the 0.9 A.
If faster connections to storage devices are the reason to consider USB 3.0, an alternative is to use instead storage devices using eSATAp and add an inexpensive bracket adding an eSATAp port to the motherboard. Some external drives support both USB (2.0 or 3.0) and eSATAp with an exchangeable adapter, so the same drive can be used with a USB 3.0 laptop. 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.
The USB Promoter Group announced the release of USB 3.0 on November 2008. On 5 January 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 were expected to enter into volume production in the first quarter of 2010. On 14 September 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 Nevada.
Windows 8 was the first Microsoft operating system to offer built in support for USB 3.0. Drivers are under development for Windows 7, but support was not included with the initial release of the operating system. However, drivers are available for Windows through manufacturer websites enable support.
Intel released its first chipset with integrated USB 3.0 ports in 2012 with the release of the Panther Point chipset. Some industry analysts have claimed that Intel was slow to integrate USB 3.0 into the chipset, thus slowing 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 (USB 3.0, PCIe 3.0, SATA 3.0) before developing a new chipset, or a tactic by Intel to favor its new Thunderbolt interface. Apple, Inc. announced laptops with USB 3.0 ports on June 11, 2012, nearly four years after USB 3.0 was finalized.
There have been many reports of USB 3.0 equipment only transferring data at USB 2.0 speed, usually with a message "This USB Mass Storage Device can transfer information faster if you connect it to a Super-Speed USB 3.0 port" on Microsoft Windows. This has been attributed to several causes, including drivers, certain cables specified as USB 3.0 (problems disappeared when a different cable was used), order of starting equipment, equipment needing to be disconnected and reconnected, and overclocked computers.
All major test-equipment vendors offer electrical-compliance test-tools meeting USB 3.0 electrical compliance. Electrical testing requires USB 3.0 test board provided type A, B, mini AB electrical compliance test breakout adapters.
Radio frequency interference
USB 3.0 devices and cables may interfere with wireless devices operating in the 2.4 GHz ISM band. This may result in a drop in throughput or complete loss of response with Bluetooth and WiFi devices.
A USB 3.0 Standard-A receptacle accepts either a USB 3.0 Standard-A plug or a USB 2.0 Standard-A plug. Conversely, it's possible to plug USB 3.0 Standard-A plug into a USB 2.0 Standard-A receptacle. Similar principle of backwards compatibility applies to connecting USB 2.0 Standard-A plug into a USB 3.0 Standard-A receptacle. The Standard-A is used for connecting to a computer port, as the host side.
Since USB 2.0 and USB 3.0 ports may coexist on the same machine and they look similar, the Standard-A USB 3.0 connector has a blue insert (Pantone 300C color). The same color-coding applies to the USB 3.0 Standard-A plug.
USB 3.0 also introduced a new Micro-B cable plug; see photo on the right. It consists of a standard USB 1.x/2.0 Micro-B cable plug, with additional 5-pin plug "stacked" on side of it. That way, USB 3.0 Micro-A host connector preserved its backwards compatibility with the USB 1.x/2.0 Micro-B cable plugs.
The connector has the same physical configuration as its predecessor but with five more pins.
The VBUS, D-, D+, and GND pins are required for USB 2.0 communication. The additional USB 3.0 pins are two differential pairs and one ground (GND_DRAIN). The two additional differential pairs are for SuperSpeed data transfer; they are used for dual simplex SuperSpeed signaling. The GND_DRAIN pin is for drain wire termination and to control EMI and maintain signal integrity.
- Computer bus
- List of computer peripheral bus bit rates
- Extensible Host Controller Interface (XHCI)
- Mobile High-Definition Link
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|Wikimedia Commons has media related to USB 3.0.|
- USB 3.0 Standard-A, Standard-B, Powered-B connectors pinouts, Pinouts guide.