USB 3.0

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USB 3.0
The Super-Speed USB logo
The Super-Speed USB logo
DesignedNovember 2008
ManufacturerUSB 3.0 Promoter Group (Hewlett-Packard, Intel, Microsoft, NEC, ST-Ericsson, and Texas Instruments)[1]
Width12 mm (A plug), 8 mm (B plug), 12.2 mm (Micro-A & Micro-B plugs)
Height4.5 mm (A plug), 10.44 mm (B plug), 1.8 mm (Micro-A & Micro-B plugs)
Max. current900 mA
Data signalYes
Bitrate5 Gbps
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USB 3.0
The Super-Speed USB logo
The Super-Speed USB logo
DesignedNovember 2008
ManufacturerUSB 3.0 Promoter Group (Hewlett-Packard, Intel, Microsoft, NEC, ST-Ericsson, and Texas Instruments)[1]
Width12 mm (A plug), 8 mm (B plug), 12.2 mm (Micro-A & Micro-B plugs)
Height4.5 mm (A plug), 10.44 mm (B plug), 1.8 mm (Micro-A & Micro-B plugs)
Max. current900 mA
Data signalYes
Bitrate5 Gbps

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 5 Gbit/s; over 10 times faster than the 480 Mbit/s top speed of USB 2.0.


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:

USB 3.0 has transmission speeds of up to 5 Gbit/s, which is 10 times faster than USB 2.0 (480 Mbit/s).

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.

Data encoding

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.[3]

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.[3]

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).[4]


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.[5] 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.[6][7]

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[8] 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. Also the new Asus laptops like the X501A. 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. However, the ExpressCard standard cannot supply power for tasks such as charging phones or powering external hard drives. Therefore, the ExpressCard (and hence the USB 3 ports) must derive power from a USB 2 port. If the ExpressCard has more than one USB 3 port then only 100 mA (milliamperes) is available from each port (contrast to typical desktop PC's being able to supply a full 0.9 A (or 900 mA) to each USB 3.0 port).[9] Additional power for multiple ports on a laptop PC may be derived in the following ways:

On the motherboards of desktop PC's which have PCI Express (PCI-e) slots (or the older PCI standard, but few are available and they are more expensive), USB 3.0 support can be added as a PCI-e expansion card. In addition to an empty PCI-e slot on the motherboard, many "PCI-e 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 amps (4.5 watts) of power that each USB 3.0 port is capable of (whilst also transmitting data), whereas the PCI-e slot itself cannot supply the 0.9 amps.

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.[7] 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.[10]

Side connectors on a laptop. Left to right: USB 3.0 host, VGA connector, DisplayPort connector, USB 2.0 host. Note the additional pins on the top side of the USB 3.0 port.


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.[7][11] Previous announcements included Gigabyte's October 2009 list of seven P55 chipset USB 3.0 motherboards,[12] and an ASUS motherboard that was cancelled before production.[13]

Commercial controllers were expected to enter into volume production in the first quarter of 2010.[14] On 14 September 2009, Freecom announced a USB 3.0 external hard drive.[15] 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.[16][17]

Drivers are under development for Windows 7, but support was not included with the initial release of the operating system.[18] 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.[19][20][21]

Windows 8 was the first operating system to offer built in support for USB 3.0.[22]

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.[23] These delays may be due to problems in the CMOS manufacturing process,[24] a focus to advance the Nehalem platform,[25] a wait to mature all the 3.0 connections standards (USB 3.0, PCIe 3.0, SATA 3.0) before developing a new chipset,[26][27] or a tactic by Intel to favor its new Thunderbolt interface.[28] Apple, Inc. announced laptops with USB 3.0 ports on June 11, 2012, nearly four years after USB 3.0 was finalized. Because Apple computers use only Intel processors and "bridge" chipsets, Intel's lack of integrated support for USB 3.0 may have proved to be a primary reason why the company didn't add support sooner.

AMD began supporting USB 3.0 with its Fusion Controller Hubs in 2011. Samsung Electronics announced support of USB 3.0 with its ARM-based Exynos 5 Dual platform intended for handheld devices.

Speed issues

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.[citation needed] All major test-equipment vendors offer electrical-compliance test-tools meeting USB 3.0 electrical compliance. Electrical testing requires USB 3.0 test board[29] 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.[30]



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 has a blue insert (Pantone 300C).

Defined interface of USB 3.0 Standard-A in blue (Pantone 300C)
USB 3.0 Standard-A and Standard-B[31]
PinColorSignal name
('A' connector)
Signal name
('B' connector)
USB 3.0 Micro-B connector
USB 3.0 Powered-B[31]
4GNDGround for Power Return
5StdB_SSTX-Superspeed transmitter differential pair
7GND_DRAINGround for signal return
8StdB_SSRX-Superspeed receiver differential pair
10DPWRPower provided by device
11DGNDGround return to DPWR
ShellShieldConnector metal

See also


  1. ^ "Intel Universal Serial Bus (USB) Frequently Asked Questions (FAQ)". Retrieved 2013-01-31.
  2. ^ Engbretson, Mike (January 2009). "USB 3.0 Physical Layer Measurements". Evaluation Engineering. Retrieved 2013-01-31.
  3. ^ a b "Universal Serial Bus Revision 3.0 Specification". Retrieved 2013-01-31.
  4. ^ Axelson, Jan. "USB 3.0 Developers FAQ". Retrieved 2013-01-31.
  5. ^ "USB‐IF" (PDF). Retrieved 2010-06-22.
  6. ^ "First Certified USB 3.0 Products Announced". PC World. 2010-01-07. Retrieved 2010-06-22.
  7. ^ a b c (PDF) SuperSpeed USB Consumer Cert Final 2, USB‐IF,
  8. ^ "USB-IF ANNOUNCES SECOND CERTIFIED USB 3.0 HOST CONTROLLER" (Press release). USB Implementers Forum, Inc.. 2010-11-16. Retrieved 2012-06-13.
  9. ^ "The Must-Know Benefits of USB 3.0". Retrieved 2013-01-10.
  10. ^ "USB 3". Lecroy. Retrieved 2010-06-22.
  11. ^ Both Gigabyte and Asus claimed the "first" USB 3.0 motherboard, Gigabyte, USA, 2010-01-04,[dead link] and Asus, USA, 2010-01-06,, while the official announcement, USB-IF, 2010-01-05,
  12. ^ Gibabyte, TW,[dead link].
  13. ^ "Asus cancels its first usb 3.0 motherboard". The Inquirer. Retrieved 2010-06-22.
  14. ^ "Digitimes". 2009-04-15. Retrieved 2010-06-22.
  15. ^ "". Retrieved 2010-06-22.[dead link]
  16. ^ Ngo, Dong (2010-01-05). "Seagate ships USB 3.0-based external hard-drive kit for laptops | CES". CNET. Retrieved 2010-06-22.
  17. ^ "BlackArmor PS 110 with USB 3.0 | Portable Hard Drive for Business with Backup Software". Seagate. Retrieved 2010-06-22.[dead link]
  18. ^ "USB in MS Windows 7 more reliable, but no 3.0 speed boost". APC Mag. Retrieved 2010-06-22.
  19. ^ "Kernel newbies". 2009-09-09. Retrieved 2010-06-22.
  20. ^ "Erste USB 3.0 Treiber [First USB 3 drivers coming with Linux 2.6.31]". DE: Heise. 2009-12-03. Retrieved 2010-06-22.
  21. ^ "First driver for USB 3.0". Linux magazine. 2009-06-09. Retrieved 2010-06-22.
  22. ^
  23. ^
  24. ^ (in German) Spekulationen über Verzögerungen bei USB 3.0, DE: Heise,
  25. ^ Paul Mah (2009-10-23). "". Retrieved 2010-06-22.
  26. ^ "FAQ — PCI Express 3.0". PCI SIG. 2009-07-01. Retrieved 2010-06-22.
  27. ^ "PCIe 3.0 Specification Coming Soon". Enterprise storage forum. 2010-05-05. Retrieved 2010-06-22.
  28. ^ "Intel delays USB 3.0 support until 2011". Techspot. 2009-10-22. Retrieved 2010-06-22.
  29. ^ USB 3.0 test board,
  30. ^ USB 3.0* Radio Frequency Interference Impact on 2.4 GHz Wireless Devices,
  31. ^ a b "USB 3.0 Interface Bus, Cable Diagram". 100806

External links