The Super-Speed USB Logo |
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| Type | USB | ||
|---|---|---|---|
| Production history | |||
| Designed | 12, 2008 | ||
| Manufacturer | Hewlett-Packard, NEC, Microsoft, Intel, and Agere Systems. | ||
| General specifications | |||
| Width | 3-6 mm | ||
| Data | |||
| Data signal | Yes | ||
USB 3.0 is the second major revision of the Universal Serial Bus (USB) standard for computer connectivity.
USB 3.0 has transmission speeds of up to 5 Gbit/s, which is 10 times faster than USB 2.0 (480 Mbit/s). USB 3.0 significantly reduces the time required for data transmission, reduces power consumption, and is backwards compatible with USB 2.0. 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.[1] 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 5 January 2010, at the Las Vegas Consumer Electronics Show (CES), including two motherboards by ASUS and Gigabyte Technology.[2][3]
Manufacturers of USB 3.0 host controllers include, but are not limited to, Renesas Electronics, Fresco Logic, Asmedia, Etron, VIA Technologies, Texas Instruments, NEC and Nvidia. As of November 2010, Renesas was the only company to have passed USB-IF certification, although Fresco Logic has now also 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 is working with Renesas to add its USB 3.0 implementation into its chipsets for its 2011 platforms. 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.
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In USB 3.0 dual-bus architecture is used to allow both USB 2.0 (HIGH Speed/LOW Speed/FULL 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, run USB 3 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.
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 a transfer mode at 5.0 Gbit/s additionally to the 3 existing transfer modes. The raw 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.
All data is sent as a stream of 8-bits which are scrambled and then converted into 10-bit format. This helps to reduce electromagnetic interference (EMI). The exactly opposite 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.
USB 3.0 support can be added to existing laptop computers with only USB 2.0 and Expresscard support by using an Expresscard-to-USB 3.0 adapter to supply USB 3.0 signal support. Although the PCI Express port that the Express card connects cannot supply power of itself, the Express card and hence the USB 3 ports nevertheless derive power from the USB 2 port that it additionally connects to as part of the interface. If the express card has more than one USB 3 port then only 100mA is available from each port. Additional power for multiple ports may be derived in the following ways:
USB 3.0 support can be added as an expansion card to a desktop motherboard with PCI Express. (Similar cards are available for the older PCI standard, but few are available and they are more expensive.) 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.[3] 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.[4]
On 5 January 2010, USB-IF announced the first two certified USB 3.0 motherboards, one by Asus and one by Gigabyte.[3][5] Previous announcements included Gigabyte's October 2009 list of seven P55 chipset USB 3.0 motherboards,[6] and an ASUS motherboard that was cancelled before production.[7]
Commercial controllers were expected to enter into volume production in the first quarter of 2010.[8] On 14 September 2009, Freecom announced a USB 3.0 external hard drive.[9] 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.[10][11]
Drivers are under development for Windows 7, but support was not included with the initial release of the operating system.[12] However, drivers are available for Windows through manufacturer websites. The Linux kernel has supported USB 3.0 since version 2.6.31, which was released in September 2009.[13][14][15]
Windows 8 will have inbuilt support for USB 3.0.[16]
Intel decided not to support USB 3.0 until 2011,[17] which will slow down mainstream adoption. Apple, Inc., a major manufacturer of computers still has yet to ship a single computer with USB 3.0 compatible ports. Apple computers made since switching from PowerPC to Intel processor technology have used only Intel processors and "bridge" chipsets because only Intel chipsets so-far support the newer EFI firmware technology required by the Mac OS X operating system software. Thus, Intel's lack of support for USB 3.0 proves to be a primary reason why Apple has yet to ship any computers with USB 3.0 capable ports. These delays may be due to problems in the CMOS manufacturing process,[18] a focus to advance the Nehalem platform,[19] a wait to mature all the 3.0 connections standards (USB 3.0, PCIe 3.0, SATA 3.0) before developing a new chipset,[20][21] or a tactic by Intel to favor its new Thunderbolt interface.[22] AMD road maps indicated that the new southbridges released in the beginning of 2010 would not support USB 3.0.[18]
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". This has been due 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.[23]
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. The Standard-A is used for connecting to the computer port.
The connector has the same physical configuration as its predecessor but with more pins for USB 3.0. The VBUS, D-, D+, and GND pins are required for USB 2.0 support, while for USB 3.0 Standard-A connector, five more pins are included–two differential pairs and one ground (GND_DRAIN). The two additional differential pairs are for SuperSpeed data transfer, that support dual simplex SuperSpeed signaling; while the GND_DRAIN pin is for drain wire termination, and to control EMI and maintain signal integrity. Since USB 2.0 and USB 3.0 ports may coexist on the same machine and look similar, the USB 3.0 connector is blue (Pantone 300C) in colour.
| Pin | Color | Signal name ('A' connector) |
Signal name ('B' connector) |
|---|---|---|---|
| 1 | Red | VBUS | |
| 2 | White | D− | |
| 3 | Green | D+ | |
| 4 | Black | GND | |
| 5 | Blue | StdA_SSRX− | StdA_SSTX− |
| 6 | Yellow | StdA_SSRX+ | StdA_SSTX+ |
| 7 | Shield | GND_DRAIN | |
| 8 | Purple | StdA_SSTX− | StdA_SSRX− |
| 9 | Orange | StdA_SSTX+ | StdA_SSRX+ |
| Shell | Shell | Shield | |
| PIN NO. | SIGNAL NAME | DESCRIPTIONS |
|---|---|---|
| 1 | VBUS | POWER |
| 2 | D- | USB 2.0 DIFFERENTIAL PAIR |
| 3 | D+ | |
| 4 | GND | Ground for Power Return |
| 5 | StdB_SSTX- | Superspeed transmitter differential pair |
| 6 | StdB_SSTX+ | |
| 7 | GND_DRAIN | Ground for signal return |
| 8 | StdB_SSRX- | Superspeed receiver differential pair |
| 9 | StdB_SSRX+ | |
| 10 | DPWR | Power provided by device |
| 11 | DGND | Ground return to DPWR |
| Shell | Shield | Connector metal |
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