USB (abbreviation of Universal Serial Bus) is an industry standard that establishes specifications for cables, connectors and protocols for connection, communication and power supply between personal computers and their peripheral devices. Released in 1996, the USB standard is currently maintained by the USB Implementers Forum (USB IF). There have been three generations of USB specifications: USB 1.x, USB 2.0 and USB 3.x; the fourth called USB4 is scheduled to be published in the middle of 2019.
|Universal Serial Bus (USB)|
The certified USB logo
|Designer||Compaq, DEC, IBM, Intel, Microsoft, NEC, and Nortel|
|Produced||Since May 1996|
|Superseded||Serial port, parallel port, game port, Apple Desktop Bus, PS/2 port, and Firewire (IEEE 1394)|
|Length||2–5 m (6 ft 7 in–16 ft 5 in) (by category)|
|Signal||5 V DC|
|Data signal||Packet data, defined by specifications|
|Bitrate||1.5; 12; 480; 5,000; 10,000; 20,000 Mbit/s (depending on mode)|
|The type-A plug (left) and type-B plug (right)|
|Pin 1||VBUS (+5 V)|
USB was designed to standardize the connection of peripherals like keyboards, pointing devices, digital still and video cameras, printers, portable media players, disk drives and network adapters to personal computers, both to communicate and to supply electric power. It has largely replaced interfaces such as serial ports and parallel ports, and has become commonplace on a wide range of devices.
USB connectors have been increasingly replacing other types for battery chargers of portable devices.
This section is intended to allow fast identification of USB receptacles (sockets) on equipment. Further diagrams and discussion of plugs and receptacles can be found in the main article above.
|Available receptacles for each connector|
|Data rate||1.5 Mbit/s
(SuperSpeed+ and Thunderbolt 3)
The Universal Serial Bus was developed to simplify and improve the interface between personal computers and peripheral devices, when compared with previously existing standard or ad-hoc proprietary interfaces.
From the computer user's perspective, the USB interface improved ease of use in several ways. The USB interface is self-configuring, so the user need not adjust settings on the device and interface for speed or data format, or configure interrupts, input/output addresses, or direct memory access channels. USB connectors are standardized at the host, so any peripheral can use any available receptacle. USB takes full advantage of the additional processing power that can be economically put into peripheral devices so that they can manage themselves; USB devices often do not have user-adjustable interface settings. The USB interface is "hot pluggable", meaning devices can be exchanged without rebooting the host computer. Small devices can be powered directly from the USB interface, displacing extra power supply cables. Because use of the USB logos is only permitted after compliance testing, the user can have confidence that a USB device will work as expected without extensive interaction with settings and configuration; the USB interface defines protocols for recovery from common errors, improving reliability over previous interfaces. Installation of a device relying on the USB standard requires minimal operator action. When a device is plugged into a port on a running personal computer system, it is either entirely automatically configured using existing device drivers, or the system prompts the user to locate a driver which is then installed and configured automatically.
For hardware manufacturers and software developers, the USB standard eliminates the requirement to develop proprietary interfaces to new peripherals. The wide range of transfer speeds available from a USB interface suits devices ranging from keyboards and mice up to streaming video interfaces. A USB interface can be designed to provide the best available latency for time-critical functions, or can be set up to do background transfers of bulk data with little impact on system resources. The USB interface is generalized with no signal lines dedicated to only one function of one device.
USB cables are limited in length, as the standard was meant to connect to peripherals on the same table-top, not between rooms or between buildings. However, a USB port can be connected to a gateway that accesses distant devices. USB has a strict "tree" topology and "master-slave" protocol for addressing peripheral devices; peripheral devices cannot interact with one another except via the host, and two hosts cannot communicate over their USB ports directly. Some extension to this limitation is possible through USB On-The-Go. A host cannot "broadcast" signals to all peripherals at once, each must be addressed individually. Some very high speed peripheral devices require sustained speeds not available in the USB standard. While converters exist between certain "legacy" interfaces and USB, they may not provide full implementation of the legacy hardware; for example, a USB to parallel port converter may work well with a printer, but not with a scanner that requires bi-directional use of the data pins.
For a product developer, use of USB requires implementation of a complex protocol and implies an "intelligent" controller in the peripheral device. Developers of USB devices intended for public sale generally must obtain a USB ID which requires a fee paid to the Implementers' Forum. Developers of products that use the USB specification must sign an agreement with Implementer's Forum. Use of the USB logos on the product require annual fees and membership in the organization.
A group of seven companies began the development of USB in 1994: Compaq, DEC, IBM, Intel, Microsoft, NEC, and Nortel. The goal was to make it fundamentally easier to connect external devices to PCs by replacing the multitude of connectors at the back of PCs, addressing the usability issues of existing interfaces, and simplifying software configuration of all devices connected to USB, as well as permitting greater data rates for external devices. Ajay Bhatt and his team worked on the standard at Intel; the first integrated circuits supporting USB were produced by Intel in 1995.
The original USB 1.0 specification, which was introduced in January 1996, defined data transfer rates of 1.5 Mbit/s Low Speed and 12 Mbit/s Full Speed. Microsoft Windows 95, OSR 2.1 provided OEM support for the devices. The first widely used version of USB was 1.1, which was released in September 1998. The 12 Mbit/s data rate was intended for higher-speed devices such as disk drives, and the lower 1.5 Mbit/s rate for low data rate devices such as joysticks. Apple Inc.'s iMac was the first mainstream product with USB and the iMac's success popularized USB itself. Following Apple's design decision to remove all legacy ports from the iMac, many PC manufacturers began building legacy-free PCs, which led to the broader PC market using USB as a standard.
The USB 2.0 specification was released in April 2000 and was ratified by the USB Implementers Forum (USB-IF) at the end of 2001. Hewlett-Packard, Intel, Lucent Technologies (now Nokia), NEC, and Philips jointly led the initiative to develop a higher data transfer rate, with the resulting specification achieving 480 Mbit/s, 40 times as fast as the original USB 1.1 specification.
The USB 3.0 specification was published on 12 November 2008. Its main goals were to increase the data transfer rate (up to 5 Gbit/s), decrease power consumption, increase power output, and be backward compatible with USB 2.0.(3–1) USB 3.0 includes a new, higher speed bus called SuperSpeed in parallel with the USB 2.0 bus.(1–3) For this reason, the new version is also called SuperSpeed. The first USB 3.0 equipped devices were presented in January 2010.
As of 2008, approximately 6 billion USB ports and interfaces were in the global marketplace, and about 2 billion were being sold each year.
The USB 3.1 specification was published in July 2013.
In December 2014, USB-IF submitted USB 3.1, USB Power Delivery 2.0 and USB Type-C specifications to the IEC (TC 100 – Audio, video and multimedia systems and equipment) for inclusion in the international standard IEC 62680 Universal Serial Bus interfaces for data and power, which is currently based on USB 2.0.
The USB 3.2 specification was published in September 2017.
Released in January 1996, USB 1.0 specified data rates of 1.5 Mbit/s (Low Bandwidth or Low Speed) and 12 Mbit/s (Full Speed). It did not allow for extension cables or pass-through monitors, due to timing and power limitations. Few USB devices made it to the market until USB 1.1 was released in August 1998. USB 1.1 was the earliest revision that was widely adopted and led to what Microsoft designated the "Legacy-free PC".
Neither USB 1.0 nor 1.1 specified a design for any connector smaller than the standard type A or type B. Though many designs for a miniaturised type B connector appeared on many peripherals, conformity to the USB 3.x standard was hampered by treating peripherals that had miniature connectors as though they had a tethered connection (that is: no plug or receptacle at the peripheral end). There was no known miniature type A connector until USB 2.0 (revision 1.01) introduced one.
USB 2.0 was released in April 2000, adding a higher maximum signaling rate of 480 Mbit/s (60 MB/s) named High Speed or High Bandwidth, in addition to the USB 1.x Full Speed signaling rate of 12 Mbit/s.
Modifications to the USB specification have been made via Engineering Change Notices (ECN). The most important of these ECNs are included into the USB 2.0 specification package available from USB.org:
The USB 3.0 specification was released on 12 November 2008, with its management transferring from USB 3.0 Promoter Group to the USB Implementers Forum (USB-IF), and announced on 17 November 2008 at the SuperSpeed USB Developers Conference.
USB 3.0 adds a SuperSpeed transfer mode, with associated backward compatible plugs, receptacles, and cables. SuperSpeed plugs and receptacles are identified with a distinct logo and blue inserts in standard format receptacles.
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. Its efficiency is dependent on a number of factors including physical symbol encoding and link level overhead. At a 5 Gbit/s (625 MByte/s) signaling rate with 8b/10b encoding, the raw throughput is 500 MByte/s. When flow control, packet framing and protocol overhead are considered, it is realistic for 400 MByte/s (3.2 Gbit/s) or more to be delivered to an application.(4–19) Communication is full-duplex in SuperSpeed transfer mode; earlier modes are half-duplex, arbitrated by the host.
Low-power and high-power devices remain operational with this standard, but devices using SuperSpeed can take advantage of increased available current of between 150 mA and 900 mA, respectively.(9–9)
USB 3.1, released in July 2013, preserves USB 3.0's SuperSpeed transfer mode under the new label of USB 3.1 Gen 1 and introduces a new SuperSpeed+ transfer mode under the label of USB 3.1 Gen 2. SuperSpeed+ doubles the maximum data signaling rate to 10 Gbit/s (1.25 GB/s), while reducing line encoding overhead to just 3% by changing the encoding scheme to 128b/132b.
USB 3.2, released in September 2017, preserves existing USB 3.1 SuperSpeed and SuperSpeed+ data modes but introduces two new SuperSpeed+ transfer modes over the USB-C connector with data rates of 10 and 20 Gbit/s (1.25 and 2.5 GB/s). The increase in bandwidth is a result of multi-lane operation over existing wires that were intended for flip-flop capabilities of the Type-C connector.
The impending release of USB4 specification was announced by USB Promoter Group in March 2019. The USB4 architecture is based on the Thunderbolt 3 protocol specification. It supports 40 Gbit/s speed and is compatible with USB 3.2, USB 2.0 and Thunderbolt 3. The architecture defines a method to share a single high-speed link with multiple end device types dynamically that best serves the transfer of data by type and application.
USB4 specification is on track to be published around the middle of 2019.
|Name||Release date||Maximum transfer rate||Note|
|USB 0.7||November 11, 1994||?||Pre-release|
|USB 0.8||December 1994||?||Pre-release|
|USB 0.9||April 13, 1995||Full Speed (12 Mbit/s)||Pre-release|
|USB 0.99||August 1995||?||Pre-release|
|USB 1.0-RC||November 1995||?||Release Candidate|
|USB 1.0||January 15, 1996||Full Speed (12 Mbit/s), Low Speed (1.5 Mbit/s)|
|USB 1.1||August 1998||Full Speed (12 Mbit/s)|
|USB 2.0||April 2000||High Speed (480 Mbit/s)|
|USB 3.0||November 2008||SuperSpeed (5 Gbit/s)||Also referred to as USB 3.1 Gen 1 and USB 3.2 Gen 1x1|
|USB 3.1||July 2013||SuperSpeed+ (10 Gbit/s)||Includes new USB 3.1 Gen 2 which is later also named USB 3.2 Gen 2x1|
|USB 3.2||September 2017||SuperSpeed+ (20 Gbit/s)||Includes new USB 3.2 Gen 1x2 and USB 3.2 Gen 2x2 multi-link modes|
|USB4||TBD Estimated Mid 2019||SuperSpeed+ & Thunderbolt 3 (40 Gbit/s)||Announced in March 2019|
|Release name||Release date||Max. power||Note|
|USB Battery Charging 2.0||2007-03-08||5 V, 1.5 A|
|USB Battery Charging 2.1||2009-04-15||?|
|USB Battery Charging 2.3||2010-12-07||5 V, 5 A|
|USB Power Delivery revision 1.0 (version 1.0)||2012-07-05||20 V, 5 A||Using FSK protocol over bus power (VBUS)|
|USB Power Delivery revision 1.0 (version 1.3)||2014-03-11||?|
|USB Type-C 2.0||2014-08-11||5 V, 3 A||New connector and cable specification|
|USB Power Delivery revision 2.0 (version 1.0)||2014-08-11||20 V, 5 A||Using BMC protocol over communication channel (CC) on type-C cables.|
|USB Type-C 4.2||2015-04-03||5 V, 3 A|
|USB Power Delivery revision 2.0 (version 1.1)||2015-05-07||20 V, 5 A|
|USB Power Delivery revision 2.0 (version 1.2)||2016-03-25||20 V, 5 A|
|USB Power Delivery revision 2.0 (version 1.3)||2017-01-12||20 V, 5 A|
|USB Power Delivery revision 3.0 (version 1.1)||2017-01-12||20 V, 5 A|
|USB Power Delivery revision 3.0 (version 1.2)||2018-06-21||20 V, 5 A|||
A USB system consists of a host with one or more downstream ports, and multiple peripherals, forming a tiered-star topology. Additional USB hubs may be included, allowing up to five tiers. A USB host may have multiple controllers, each with one or more ports. Up to 127 devices may be connected to a single host controller.(8–29) USB devices are linked in series through hubs. The hub built into the host controller is called the root hub.
A USB device may consist of several logical sub-devices that are referred to as device functions. A composite device may provide several functions, for example, a webcam (video device function) with a built-in microphone (audio device function). An alternative to this is a compound device, in which the host assigns each logical device a distinct address and all logical devices connect to a built-in hub that connects to the physical USB cable.
USB device communication is based on pipes (logical channels). A pipe is a connection from the host controller to a logical entity within a device, called an endpoint. Because pipes correspond to endpoints, the terms are sometimes used interchangeably. Each USB device can have up to 32 endpoints (16 in and 16 out), though it is rare to have so many. Endpoints are defined and numbered by the device during initialization (the period after physical connection called "enumeration") and so are relatively permanent, whereas pipes may be opened and closed.
There are two types of pipe: stream and message.
When a host starts a data transfer, it sends a TOKEN packet containing an endpoint specified with a tuple of (device_address, endpoint_number). If the transfer is from the host to the endpoint, the host sends an OUT packet (a specialization of a TOKEN packet) with the desired device address and endpoint number. If the data transfer is from the device to the host, the host sends an IN packet instead. If the destination endpoint is a uni-directional endpoint whose manufacturer's designated direction does not match the TOKEN packet (e.g. the manufacturer's designated direction is IN while the TOKEN packet is an OUT packet), the TOKEN packet is ignored. Otherwise, it is accepted and the data transaction can start. A bi-directional endpoint, on the other hand, accepts both IN and OUT packets.
Endpoints are grouped into interfaces and each interface is associated with a single device function. An exception to this is endpoint zero, which is used for device configuration and is not associated with any interface. A single device function composed of independently controlled interfaces is called a composite device. A composite device only has a single device address because the host only assigns a device address to a function.
When a USB device is first connected to a USB host, the USB device enumeration process is started. The enumeration starts by sending a reset signal to the USB device. The data rate of the USB device is determined during the reset signaling. After reset, the USB device's information is read by the host and the device is assigned a unique 7-bit address. If the device is supported by the host, the device drivers needed for communicating with the device are loaded and the device is set to a configured state. If the USB host is restarted, the enumeration process is repeated for all connected devices.
The host controller directs traffic flow to devices, so no USB device can transfer any data on the bus without an explicit request from the host controller. In USB 2.0, the host controller polls the bus for traffic, usually in a round-robin fashion. The throughput of each USB port is determined by the slower speed of either the USB port or the USB device connected to the port.
High-speed USB 2.0 hubs contain devices called transaction translators that convert between high-speed USB 2.0 buses and full and low speed buses. There may be one translator per hub or per port.
Because there are two separate controllers in each USB 3.0 host, USB 3.0 devices transmit and receive at USB 3.0 data rates regardless of USB 2.0 or earlier devices connected to that host. Operating data rates for earlier devices are set in the legacy manner.
The functionality of a USB device is defined by a class code sent to a USB host. This allows the host to load software modules for the device and to support new devices from different manufacturers.
Device classes include:
|Class||Usage||Description||Examples, or exception|
|00h||Device||Unspecified||Device class is unspecified, interface descriptors are used to determine needed drivers|
|01h||Interface||Audio||Speaker, microphone, sound card, MIDI|
|02h||Both||Communications and CDC Control||Modem, Ethernet adapter, Wi-Fi adapter, RS-232 serial adapter. Used together with class 0Ah (CDC-Data, below)|
|03h||Interface||Human interface device (HID)||Keyboard, mouse, joystick|
|05h||Interface||Physical Interface Device (PID)||Force feedback joystick|
|06h||Interface||Image (PTP/MTP)||Webcam, scanner|
|07h||Interface||Printer||Laser printer, inkjet printer, CNC machine|
|08h||Interface||Mass storage (MSC or UMS)||USB flash drive, memory card reader, digital audio player, digital camera, external drive|
|09h||Device||USB hub||Full bandwidth hub|
|0Ah||Interface||CDC-Data||Used together with class 02h (Communications and CDC Control, above)|
|0Bh||Interface||Smart Card||USB smart card reader|
|0Dh||Interface||Content security||Fingerprint reader|
|0Fh||Interface||Personal healthcare device class (PHDC)||Pulse monitor (watch)|
|10h||Interface||Audio/Video (AV)||Webcam, TV|
|11h||Device||Billboard||Describes USB Type-C alternate modes supported by device|
|DCh||Both||Diagnostic Device||USB compliance testing device|
|E0h||Interface||Wireless Controller||Bluetooth adapter, Microsoft RNDIS|
|FEh||Interface||Application-specific||IrDA Bridge, Test & Measurement Class (USBTMC), USB DFU (Device Firmware Upgrade)|
|FFh||Both||Vendor-specific||Indicates that a device needs vendor-specific drivers|
USB mass storage device class (MSC or UMS) standardizes connections to storage devices. At first intended for magnetic and optical drives, it has been extended to support flash drives. It has also been extended to support a wide variety of novel devices as many systems can be controlled with the familiar metaphor of file manipulation within directories. The process of making a novel device look like a familiar device is also known as extension. The ability to boot a write-locked SD card with a USB adapter is particularly advantageous for maintaining the integrity and non-corruptible, pristine state of the booting medium.
Though most personal computers since mid-2004 can boot from USB mass storage devices, USB is not intended as a primary bus for a computer's internal storage. However, USB has the advantage of allowing hot-swapping, making it useful for mobile peripherals, including drives of various kinds.
Several manufacturers offer external portable USB hard disk drives, or empty enclosures for disk drives. These offer performance comparable to internal drives, limited by the current number and types of attached USB devices, and by the upper limit of the USB interface. Other competing standards for external drive connectivity include eSATA, ExpressCard, FireWire (IEEE 1394), and most recently Thunderbolt.
Media Transfer Protocol (MTP) was designed by Microsoft to give higher-level access to a device's filesystem than USB mass storage, at the level of files rather than disk blocks. It also has optional DRM features. MTP was designed for use with portable media players, but it has since been adopted as the primary storage access protocol of the Android operating system from the version 4.1 Jelly Bean as well as Windows Phone 8 (Windows Phone 7 devices had used the Zune protocol—an evolution of MTP). The primary reason for this is that MTP does not require exclusive access to the storage device the way UMS does, alleviating potential problems should an Android program request the storage while it is attached to a computer. The main drawback is that MTP is not as well supported outside of Windows operating systems.
Joysticks, keypads, tablets and other human-interface devices (HIDs) are also progressively migrating from MIDI, and PC game port connectors to USB.
USB mice and keyboards can usually be used with older computers that have PS/2 connectors with the aid of a small USB-to-PS/2 adapter. For mice and keyboards with dual-protocol support, an adaptor that contains no logic circuitry may be used: the USB hardware in the keyboard or mouse is designed to detect whether it is connected to a USB or PS/2 port, and communicate using the appropriate protocol. Converters also exist that connect PS/2 keyboards and mice (usually one of each) to a USB port. These devices present two HID endpoints to the system and use a microcontroller to perform bidirectional data translation between the two standards.
Device Firmware Upgrade (DFU) is a vendor- and device-independent mechanism for upgrading the firmware of USB devices with improved versions provided by their manufacturers, offering (for example) a way to deploy firmware bug fixes. During the firmware upgrade operation, USB devices change their operating mode effectively becoming a PROM programmer. Any class of USB device can implement this capability by following the official DFU specifications.
In addition to its intended legitimate purposes, DFU can also be exploited by uploading maliciously crafted firmware that causes USB devices to spoof various other device types; one such exploiting approach is known as BadUSB.
The USB Device Working Group has laid out specifications for audio streaming, and specific standards have been developed and implemented for audio class uses, such as microphones, speakers, headsets, telephones, musical instruments, etc. The DWG has published three versions of audio device specifications: Audio 1.0, 2.0, and 3.0, referred to as "UAC" or "ADC".
UAC 2.0 introduced support for High Speed USB (in addition to Full Speed), allowing greater bandwidth for multi-channel interfaces, higher sample rates, lower inherent latency, and 8× improvement in timing resolution in synchronous and adaptive modes. UAC2 also introduces the concept of clock domains, which provides information to the host about which input and output terminals derive their clocks from the same source, as well as improved support for audio encodings like DSD, audio effects, channel clustering, user controls, and device descriptions.
UAC 3.0 primarily introduces improvements for portable devices, such as reduced power usage by bursting the data and staying in low power mode more often, and power domains for different components of the device, allowing them to be shut down when not in use.
UAC 1.0 devices are still common, however, due to their cross-platform driverless compatibility, and also partly due to Microsoft's failure to implement UAC 2.0 for over a decade after its publication, having finally added support to Windows 10 through the Creators Update on 20 March 2017. UAC 2.0 is also supported by MacOS, iOS, and Linux, however Android also only implements a subset of UAC 1.0.
While the USB spec originally described asynchronous mode being used in "low cost speakers" and adaptive mode in "high-end digital speakers", the opposite perception exists in the hi-fi world, where asynchronous mode is advertised as a feature, and adaptive/synchronous modes have a bad reputation. In reality, all the types can be high-quality or low-quality, depending on the quality of their engineering and the application. Asynchronous has the benefit of being untied from the computer's clock, but the disadvantage of requiring sample rate conversion when combining multiple sources.
The connectors the USB committee specifies support a number of USB's underlying goals, and reflect lessons learned from the many connectors the computer industry has used. The female connector mounted on the host or device is called the receptacle, and the male connector attached to the cable is called the plug.(2–5 – 2–6) The official USB specification documents also periodically define the term male to represent the plug, and female to represent the receptacle.
By design, it is difficult to insert a USB plug into its receptacle incorrectly. The USB specification requires that the cable plug and receptacle be marked so the user can recognize the proper orientation. The type-C plug is reversible. USB cables and small USB devices are held in place by the gripping force from the receptacle, with no screws, clips, or thumb-turns as some connectors use.
The different A and B plugs prevent accidentally connecting two power sources. However, some of this directed topology is lost with the advent of multi-purpose USB connections (such as USB On-The-Go in smartphones, and USB-powered Wi-Fi routers), which require A-to-A, B-to-B, and sometimes Y/splitter cables.
USB connector types multiplied as the specification progressed. The original USB specification detailed standard-A and standard-B plugs and receptacles. The connectors were different so that users could not connect one computer receptacle to another. The data pins in the standard plugs are recessed compared to the power pins, so that the device can power up before establishing a data connection. Some devices operate in different modes depending on whether the data connection is made. Charging docks supply power and do not include a host device or data pins, allowing any capable USB device to charge or operate from a standard USB cable. Charging cables provide power connections, but not data. In a charge-only cable, the data wires are shorted at the device end, otherwise the device may reject the charger as unsuitable.
The USB 1.1 standard specifies that a standard cable can have a maximum length of 5 meters (16 ft 5 in) with devices operating at full speed (12 Mbit/s), and a maximum length of 3 meters (9 ft 10 in) with devices operating at low speed (1.5 Mbit/s).
USB 2.0 provides for a maximum cable length of 5 meters (16 ft 5 in) for devices running at high speed (480 Mbit/s).
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 ft 10 in).
USB supplies power at 5 V ± 5% to power USB downstream devices.
Low-power devices (such as a typical USB keyboard) may draw at most 1 unit load (1 unit load is 100 mA for USB devices up to USB 2.0, while USB 3.0 defines a unit load as 150 mA), and all devices must act as Low-power devices when starting out as unconfigured.
High-power devices (such as a typical 2.5-inch USB Hard Drive) draw at least 1 unit load and at most 5 unit loads (500 mA) for devices up to USB 2.0 or 6 unit loads (900 mA) for SuperSpeed devices.
|Low-power device||100 mA||5 V[a]||0.50 W|
|Low-power SuperSpeed (USB 3.0) device||150 mA||5 V[a]||0.75 W|
|High-power device||500 mA[b]||5 V||2.5 W|
|High-power SuperSpeed (USB 3.0) device||900 mA[c]||5 V||4.5 W|
|Multi-lane SuperSpeed (USB 3.2 Gen x2) device||1.5 A[d]||5 V||7.5 W|
|Battery Charging (BC) 1.2||1.5 A||5 V||7.5 W|
|Type-C||1.5 A||5 V||7.5 W|
|3 A||5 V||15 W|
|Power Delivery 2.0 Micro-USB||3 A||20 V||60 W|
|Power Delivery 2.0 Type-A/B/C[e]||5 A||20 V||100 W|
To recognize Battery Charging, a dedicated charging port places a resistance not exceeding 200 Ω across the D+ and D− terminals.
In addition to standard USB, there is a proprietary high-powered system known as PoweredUSB, developed in the 1990s, and mainly used in point-of-sale terminals such as cash registers.
A USB connection is always between a host or hub at the A connector end, and a device or hub's "upstream" port at the other end.
During USB communication, data is transmitted as packets. Initially, all packets are sent from the host via the root hub, and possibly more hubs, to devices. Some of those packets direct a device to send some packets in reply.
The basic transactions of USB are:
The USB Implementers Forum is working on a wireless networking standard based on the USB protocol. Wireless USB is a cable-replacement technology, and uses ultra-wideband wireless technology for data rates of up to 480 Mbit/s.
InterChip USB is a chip-to-chip variant that eliminates the conventional transceivers found in normal USB. The HSIC physical layer uses about 50% less power and 75% less board area compared to USB 2.0.
At first, USB was considered a complement to IEEE 1394 (FireWire) technology, which was designed as a high-bandwidth serial bus that efficiently interconnects peripherals such as disk drives, audio interfaces, and video equipment. In the initial design, USB operated at a far lower data rate and used less sophisticated hardware. It was suitable for small peripherals such as keyboards and pointing devices.
The most significant technical differences between FireWire and USB include:
These and other differences reflect the differing design goals of the two buses: USB was designed for simplicity and low cost, while FireWire was designed for high performance, particularly in time-sensitive applications such as audio and video. Although similar in theoretical maximum transfer rate, FireWire 400 is faster than USB 2.0 high-bandwidth in real-use, especially in high-bandwidth use such as external hard drives. The newer FireWire 800 standard is twice as fast as FireWire 400 and faster than USB 2.0 high-bandwidth both theoretically and practically. However, FireWire's speed advantages rely on low-level techniques such as direct memory access (DMA), which in turn have created opportunities for security exploits such as the DMA attack.
The chipset and drivers used to implement USB and FireWire have a crucial impact on how much of the bandwidth prescribed by the specification is achieved in the real world, along with compatibility with peripherals.
The IEEE 802.3af, at, and bt Power over Ethernet (PoE) standards specifiy more elaborate power negotiation schemes than powered USB. They operate at 48 V DC and can supply more power (up to 12.95 W for af, 25.5 W for at aka PoE+, 71 W for bt aka 4PPoE) over a cable up to 100 meters compared to USB 2.0, which provides 2.5 W with a maximum cable length of 5 meters. This has made PoE popular for VoIP telephones, security cameras, wireless access points, and other networked devices within buildings. However, USB is cheaper than PoE provided that the distance is short and power demand is low.
Ethernet standards require electrical isolation between the networked device (computer, phone, etc.) and the network cable up to 1500 V AC or 2250 V DC for 60 seconds. USB has no such requirement as it was designed for peripherals closely associated with a host computer, and in fact it connects the peripheral and host grounds. This gives Ethernet a significant safety advantage over USB with peripherals such as cable and DSL modems connected to external wiring that can assume hazardous voltages under certain fault conditions.
The USB Device Class Definition for MIDI Devices allows Music Instrument Digital Interface (MIDI) music data to be sent over USB. The MIDI capability is extended to allow up to sixteen simultaneous virtual MIDI cables, each of which can carry the usual MIDI sixteen channels and clocks.
USB is competitive for low-cost and physically adjacent devices. However, Power over Ethernet and the MIDI plug standard have an advantage in high-end devices that may have long cables. USB can cause ground loop problems between equipment, because it connects ground references on both transceivers. By contrast, the MIDI plug standard and Ethernet have built-in isolation to 500V or more.
The eSATA connector is a more robust SATA connector, intended for connection to external hard drives and SSDs. eSATA's transfer rate (up to 6 Gbit/s) is similar to that of USB 3.0 (up to 5 Gbit/s on current devices; 10 Gbit/s speeds via USB 3.1, announced on 31 July 2013). A device connected by eSATA appears as an ordinary SATA device, giving both full performance and full compatibility associated with internal drives.
eSATA does not supply power to external devices. This is an increasing disadvantage compared to USB. Even though USB 3.0's 4.5 W is sometimes insufficient to power external hard drives, technology is advancing and external drives gradually need less power, diminishing the eSATA advantage. eSATAp (power over eSATA; aka ESATA/USB) is a connector introduced in 2009 that supplies power to attached devices using a new, backward compatible, connector. On a notebook eSATAp usually supplies only 5 V to power a 2.5-inch HDD/SSD; on a desktop workstation it can additionally supply 12 V to power larger devices including 3.5-inch HDD/SSD and 5.25-inch optical drives.
eSATAp support can be added to a desktop machine in the form of a bracket connecting the motherboard SATA, power, and USB resources.
eSATA, like USB, supports hot plugging, although this might be limited by OS drivers and device firmware.
Thunderbolt combines PCI Express and Mini DisplayPort into a new serial data interface. Original Thunderbolt implementations have two channels, each with a transfer speed of 10 Gbit/s, resulting in an aggregate unidirectional bandwidth of 20 Gbit/s.
Thunderbolt 2 uses link aggregation to combine the two 10 Gbit/s channels into one bi-directional 20 Gbit/s channel.
Thunderbolt 3 uses the USB Type-C connector. Thunderbolt 3 has two physical 20Gb/s bi-directional channels, aggregated to appear as a single logical 40Gb/s bi-directional channel. Thunderbolt 3 controllers a incorporate USB 3.1 Gen 2 controller to provide compatibility with USB devices. They are also capable of providing DisplayPort alternate mode over the USB Type-C connector, making a Thunderbolt 3 port a superset of a USB 3.1 Gen 2 port with DisplayPort alternate mode.
The Thunderbolt 3 protocol has been adopted into the USB4 standard after being released by Intel Corporation. If implemented correctly, USB4 ports should function identically to Thunderbolt 3 ports in most circumstances. However, USB4 will provide backwards compatibility with USB 3.2 Gen 2x2 devices. No Thunderbolt 3 controller has been built to provide USB 3.2 Gen 2x2 support, as of the Titan Ridge (2019) Thunderbolt controllers. No information pertaining to VirtualLink alternate mode compatibility with either Thunderbolt 3 or USB4 has been published, as of April 2019.
Various protocol converters are available that convert USB data signals to and from other communications standards.
Body length is fully 12 mm in width by 4.5 mm in height with no deviations
ZDNet xiamiwas invoked but never defined (see the help page).
In applications where streaming latency is important, UAC2 offers up to an 8x reduction over UAC1. ... Each clocking method has pros and cons and best-fit applications.
ADC-2 refers to the USB Device Class Definition for Audio Devices, Release 2.0.
All operating systems (Win, OSX, and Linux) support USB Audio Class 1 natively. This means you don’t need to install drivers, it is plug&play.
Note that Full Speed USB has a much higher intrinsic latency of 2ms
Class 2 support enables much higher sample rates such as PCM 24 bit / 384 kHz and DSD (DoP) up through DSD256.
We now have native support for USB Audio 2.0 devices with an inbox class driver! This is an early version of the driver that does not have all features enabled
Synchronous sub-mode is not commonly used with audio because both host and peripheral are at the mercy of the USB clock.
The PCM2906C employs SpAct™ architecture, TI's unique system that recovers the audio clock from USB packet data.
Early USB replay interfaces used synchronous mode but acquired a reputation for poor quality of the recovered clock (and resultant poor replay quality). This was primarily due to deficiencies of clocking implementation rather than inherent shortcomings of the approach.
The fact that there is no clock line within the USB cable leads to a thinner cable which is an advantage. But, no matter how good the crystal oscillators are at the send and receive ends, there will always be some difference between the two...
Synchronous USB DAC is the lowest quality of the three ... Adaptive ... means that there is no continuous, accurate master clock in the DAC, which causes jitter in the audio stream. ... Asynchronous – this is the most complex to implement but it is a huge improvement on the other types.
Synchronous is not used in a quality DAC as it is very jittery. ... asynchronous is the better of these modes.
Some manufacturers may lead you to believe that Asynchronous USB transfers are superior to Adaptive USB transfers and that therefore you must believe in the asynchronous solution. This no more true than saying that you "must" hold the fork in your left hand. In fact, if you know what you are doing, you will feed yourself with either hand. The issue is really about good engineering practices.
The Apple USB Modem is a combined 56 kbit/s data modem and 14.4 kbit/s fax external USB modem introduced by Apple Inc. after the internal 56k modem was dropped on the October 12, 2005 iMac G5 revision. While it looks similar, it should not be confused with Apple's optional USB Ethernet Adapter accessory, available for its MacBook Air and MacBook Pro Retina range of laptops since 2008.Comparison of open-source wireless drivers
Wireless network cards for computers require control software to make them function (firmware, device drivers). This is a list of the status of some open-source drivers for 802.11 wireless network cards.Computer keyboard
In computing, a computer keyboard is a typewriter-style device which uses an arrangement of buttons or keys to act as mechanical levers or electronic switches. Following the decline of punch cards and paper tape, interaction via teleprinter-style keyboards became the main input method for computers.
Keyboard keys (buttons) typically have characters engraved or printed on them, and each press of a key typically corresponds to a single written symbol. However, producing some symbols may require pressing and holding several keys simultaneously or in sequence. While most keyboard keys produce letters, numbers or signs (characters), other keys or simultaneous key presses can produce actions or execute computer commands.
In normal usage, the keyboard is used as a text entry interface for typing text and numbers into a word processor, text editor or any other program. In a modern computer, the interpretation of key presses is generally left to the software. A computer keyboard distinguishes each physical key from every other key and reports all key presses to the controlling software. Keyboards are also used for computer gaming — either regular keyboards or keyboards with special gaming features, which can expedite frequently used keystroke combinations.
A keyboard is also used to give commands to the operating system of a computer, such as Windows' Control-Alt-Delete combination. Although on Pre-Windows 95 Microsoft operating systems this forced a re-boot, now it brings up a system security options screen.A command-line interface is a type of user interface navigated entirely using a keyboard, or some other similar device that does the job of one.ExpressCard
ExpressCard, initially called NEWCARD, is an interface to connect peripheral devices to a computer, usually a laptop computer. The ExpressCard technical standard specifies the design of slots built into the computer and of expansion cards to insert in the slots. The cards contain electronic circuits and sometimes connectors for external devices. The ExpressCard standard replaces the PC Card (also known as PCMCIA) standards.
ExpressCards can connect a variety of devices to a computer including mobile broadband modems (sometimes called connect cards), IEEE 1394 (FireWire) connectors, USB connectors, Ethernet network ports, Serial ATA storage devices, solid-state drives, external enclosures for desktop-size PCI Express graphics cards and other peripheral devices, wireless network interface controllers (NIC), TV tuner cards, Common Access Card (CAC) readers, and sound cards.Hard disk drive
A hard disk drive (HDD), hard disk, hard drive, or fixed disk, is an electro-mechanical data storage device that uses magnetic storage to store and retrieve digital information using one or more rigid rapidly rotating disks (platters) coated with magnetic material. The platters are paired with magnetic heads, usually arranged on a moving actuator arm, which read and write data to the platter surfaces. Data is accessed in a random-access manner, meaning that individual blocks of data can be stored or retrieved in any order and not only sequentially. HDDs are a type of non-volatile storage, retaining stored data even when powered off.Introduced by IBM in 1956, HDDs became the dominant secondary storage device for general-purpose computers by the early 1960s. Continuously improved, HDDs have maintained this position into the modern era of servers and personal computers. More than 200 companies have produced HDDs historically, though after extensive industry consolidation most units are manufactured by Seagate, Toshiba, and Western Digital. HDDs dominate the volume of storage produced (exabytes per year) for servers. Though production is growing slowly, sales revenues and unit shipments are declining because solid-state drives (SSDs) have higher data-transfer rates, higher areal storage density, better reliability, and much lower latency and access times.The revenues for SSDs, most of which use NAND, slightly exceed those for HDDs. Though SSDs have nearly 10 times higher cost per bit, they are replacing HDDs in applications where speed, power consumption, small size, and durability are important.The primary characteristics of an HDD are its capacity and performance. Capacity is specified in unit prefixes corresponding to powers of 1000: a 1-terabyte (TB) drive has a capacity of 1,000 gigabytes (GB; where 1 gigabyte = 1 billion bytes). Typically, some of an HDD's capacity is unavailable to the user because it is used by the file system and the computer operating system, and possibly inbuilt redundancy for error correction and recovery. Also there is confusion regarding storage capacity, since capacities are stated in decimal Gigabytes (powers of 10) by HDD manufacturers, whereas some operating systems report capacities in binary Gibibytes, which results in a smaller number than advertised. Performance is specified by the time required to move the heads to a track or cylinder (average access time) adding the time it takes for the desired sector to move under the head (average latency, which is a function of the physical rotational speed in revolutions per minute), and finally the speed at which the data is transmitted (data rate).
The two most common form factors for modern HDDs are 3.5-inch, for desktop computers, and 2.5-inch, primarily for laptops. HDDs are connected to systems by standard interface cables such as PATA (Parallel ATA), SATA (Serial ATA), USB or SAS (Serial Attached SCSI) cables.IBook
iBook is a line of laptop computers designed, manufactured, and sold by Apple Computer, Inc. from 1999 to 2006. The line targeted entry-level, consumer and education markets, with lower specifications and prices than the PowerBook, Apple's higher-end line of laptop computers. It was the first mass consumer product to offer Wi-Fi network connectivity, which was then branded by Apple as AirPort.The iBook had three different designs during its lifetime. The first, known as the "Clamshell", was inspired by the design of Apple's popular iMac line at the time. It was a significant departure from previous portable computer designs due to its shape, bright colors, incorporation of a handle into the casing, lack of a display closing latch, lack of a hinged cover over the external ports and built-in wireless networking. Two years later, the second generation abandoned the original form factor in favor of a more conventional, rectangular design. In October 2003, the third generation was introduced, adding a PowerPC G4 chip, USB 2.0 and a slot-loading drive.
They were very popular in education, with Henrico County Public Schools being the first of many school systems in the United States to distribute one to every student.
Apple replaced the iBook line with the MacBook in May 2006 during Apple's transition to Intel processors.IEEE 1394
IEEE 1394 is an interface standard for a serial bus for high-speed communications and isochronous real-time data transfer. It was developed in the late 1980s and early 1990s by Apple, which called it FireWire. The 1394 interface is also known by the brands i.LINK (Sony), and Lynx (Texas Instruments).
The copper cable it uses in its most common implementation can be up to 4.5 metres (15 ft) long. Power is also carried over this cable, allowing devices with moderate power requirements to operate without a separate power supply. FireWire is also available in Cat 5 and optical fiber versions.
The 1394 interface is comparable to USB. USB was developed subsequently and gained much greater market share. USB also requires a master controller whereas IEEE 1394 is cooperatively managed by the connected devices.Live USB
A live USB is a USB flash drive or external hard disk drive containing a full operating system that can be booted. They are the evolutionary next step after live CDs, but with the added benefit of writable storage on the live USB itself, allowing customizations to the booted operating system. Live USBs can be used in embedded systems for system administration, data recovery, or test driving, and can persistently save settings and install software packages on the USB device.
Many operating systems including Mac OS 9, macOS, Windows XP Embedded and a large portion of Linux and BSD distributions can run from a USB flash drive, and Windows 8 Enterprise has a feature titled Windows To Go for a similar purpose.Nintendo Wi-Fi USB Connector
The Nintendo Wi-Fi USB Connector is a wireless game adapter, developed jointly by Nintendo and Buffalo Technology, which allows Nintendo DSi and Wii users without a Wi-Fi connection or compatible Wi-Fi network to establish one via a broadband-connected PC. Inserted into the host PC's USB port, the connector functions with the Nintendo DS, Wii, and DSi, permitting the user to connect to the Internet to play Nintendo Wi-Fi Connection games and access various other online functionality. The product was the best selling Nintendo accessory to date, according to the official Nintendo site on 15 November 2007, but was discontinued in the same month until further notice. On September 8, 2008, Nintendo announced the Nintendo Wi-Fi Network Adapter, an 802.11g wireless router/bridge which serves a similar purpose.PlayStation 3 accessories
Various accessories for the PlayStation 3 video game console have been produced by Sony. These include controllers, audio and video input devices like microphones, video cameras, and cables for better sound and picture quality.Thunderbolt (interface)
Thunderbolt is the brand name of a hardware interface developed by Intel (in collaboration with Apple) that allows the connection of external peripherals to a computer. Thunderbolt 1 and 2 use the same connector as Mini DisplayPort (MDP), whereas Thunderbolt 3 re-uses the Type-C connector from USB. It was initially developed and marketed under the name Light Peak, and first sold as part of a consumer product on 24 February 2011.Thunderbolt combines PCI Express (PCIe) and DisplayPort (DP) into two serial signals, and additionally provides DC power, all in one cable. Up to six peripherals may be supported by one connector through various topologies.USB-C
USB-C, formally known as USB Type-C, is a 24-pin USB connector system, which is distinguished by its two-fold rotationally-symmetrical connector.The USB Type-C Specification 1.0 was published by the USB Implementers Forum (USB-IF) and was finalized in August 2014. It was developed at roughly the same time as the USB 3.1 specification. In July 2016, it was adopted by the IEC as "IEC 62680-1-3".A device with a Type-C connector does not necessarily implement USB 3.1, USB Power Delivery, or any Alternate Mode: the Type-C connector is common to several technologies while mandating only a few of them.USB 3.2, released in September 2017, replaces the USB 3.1 standard. It preserves existing USB 3.1 SuperSpeed and SuperSpeed+ data modes and introduces two new SuperSpeed+ transfer modes over the USB-C connector using two-lane operation, with data rates of 10 and 20 Gbit/s (1250 and 2500 MB/s).USB 3.0
USB 3.0 is the third major version of the Universal Serial Bus (USB) standard for interfacing computers and electronic devices. Among other improvements, USB 3.0 adds the new transfer rate referred to as SuperSpeed USB (SS) that can transfer data at up to 5 Gbit/s (625 MB/s), which is about 10 times faster than the USB 2.0 standard. It is recommended that manufacturers distinguish USB 3.0 connectors from their USB 2.0 counterparts by using blue color for the Standard-A receptacles and plugs, and by the initials SS.USB 3.1, released in July 2013, is the successor standard that replaces the USB 3.0 standard. USB 3.1 preserves the existing SuperSpeed transfer rate, giving it the new label USB 3.1 Gen 1, while defining a new SuperSpeed+ transfer mode, called USB 3.1 Gen 2 which can transfer data at up to 10 Gbit/s over the existing USB-type-A and USB-C connectors (1250 MB/s, twice the rate of USB 3.0).USB 3.2, released in September 2017, replaces the USB 3.1 standard. It preserves existing USB 3.1 SuperSpeed and SuperSpeed+ data modes and introduces two new SuperSpeed+ transfer modes over the USB-C connector using two-lane operation, with data rates of 10 and 20 Gbit/s (1250 and 2500 MB/s).USB On-The-Go
USB On-The-Go, often abbreviated to USB OTG or just OTG, is a specification first used in late 2001 that allows USB devices, such as tablets or smartphones, to act as a host, allowing other USB devices, such as USB flash drives, digital cameras, mice or keyboards, to be attached to them. Use of USB OTG allows those devices to switch back and forth between the roles of host and device. A mobile phone may read from removable media as the host device, but present itself as a USB Mass Storage Device when connected to a host computer.
USB OTG introduces the concept of a device performing both master and slave roles – whenever two USB devices are connected and one of them is a USB OTG device, they establish a communication link. The device controlling the link is called the master or host, while the other is called the slave or peripheral.
USB OTG defines two roles for devices: OTG A-device and OTG B-device, specifying which side supplies power to the link, and which initially is the host. The OTG A-device is a power supplier, and an OTG B-device is a power consumer. In the default link configuration, the A-device acts as a USB host with the B-device acting as a USB peripheral. The host and peripheral modes may be exchanged later by using Host Negotiation Protocol (HNP).
The initial role of each device is defined by which mini plug a user inserts into its receptacle.USB flash drive
A USB flash drive, also known as a thumb drive, pen drive, gig stick, flash stick, jump drive, disk key, disk on key (after the original M-Systems DiskOnKey drive from 2000), flash-drive, memory stick (not to be confused with the Sony Memory Stick), USB key, USB stick or USB memory, is a data storage device that includes flash memory with an integrated USB interface. It is typically removable, rewritable and much smaller than an optical disc. Most weigh less than 1 oz (28 grams). Since first appearing on the market in late 2000, as with virtually all other computer memory devices, storage capacities have risen while prices have dropped. As of March 2016, flash drives with anywhere from 8 to 256 GB were frequently sold, while 512 GB and 1 TB units were less frequent. As of 2018, 2TB flash drives were the largest available in terms of storage capacity. Some allow up to 100,000 write/erase cycles, depending on the exact type of memory chip used, and are thought to last between 10 and 100 years under normal circumstances (shelf storage time).
USB flash drives are often used for storage, data back-up and transfer of computer files. Compared with floppy disks or CDs, they are smaller, faster, have significantly more capacity, and are more durable due to a lack of moving parts. Additionally, they are immune to electromagnetic interference (unlike floppy disks), and are unharmed by surface scratches (unlike CDs). Until about 2005, most desktop and laptop computers were supplied with floppy disk drives in addition to USB ports, but floppy disk drives became obsolete after widespread adoption of USB ports and the larger USB drive capacity compared to the 1.44 MB 3.5-inch floppy disk.
USB flash drives use the USB mass storage device class standard, supported natively by modern operating systems such as Windows, Linux, macOS and other Unix-like systems, as well as many BIOS boot ROMs. USB drives with USB 2.0 support can store more data and transfer faster than much larger optical disc drives like CD-RW or DVD-RW drives and can be read by many other systems such as the Xbox One, PlayStation 4, DVD players, automobile entertainment systems, and in a number of handheld devices such as smartphones and tablet computers, though the electronically similar SD card is better suited for those devices.
A flash drive consists of a small printed circuit board carrying the circuit elements and a USB connector, insulated electrically and protected inside a plastic, metal, or rubberized case, which can be carried in a pocket or on a key chain, for example. The USB connector may be protected by a removable cap or by retracting into the body of the drive, although it is not likely to be damaged if unprotected. Most flash drives use a standard type-A USB connection allowing connection with a port on a personal computer, but drives for other interfaces also exist. USB flash drives draw power from the computer via the USB connection. Some devices combine the functionality of a portable media player with USB flash storage; they require a battery only when used to play music on the go.USB hardware
This article provides information about the physical aspects of Universal Serial Bus, USB: connectors, cabling, and power. The initial versions of the USB standard specified connectors that were easy to use and that would have acceptable life spans; revisions of the standard added smaller connectors useful for compact portable devices. Higher-speed development of the USB standard gave rise to another family of connectors to permit additional data paths. All versions of USB specify cable properties; version 3.X cables include additional data paths. The USB standard included power supply to peripheral devices; modern versions of the standard extend the power delivery limits for battery charging and devices requiring up to 100 watts. USB has been selected as the standard charging format for many mobile phones, reducing the proliferation of proprietary chargers.USB mass storage device class
The USB mass storage device class (also known as USB MSC or UMS) is a set of computing communications protocols defined by the USB Implementers Forum that makes a USB device accessible to a host computing device and enables file transfers between the host and the USB device. To a host, the USB device acts as an external hard drive; the protocol set interfaces with a number of storage devices.Webcam
A webcam is a video camera that feeds or streams its image in real time to or through a computer to a computer network.
The term "webcam" (a clipped compound) may also be used in its original sense of a video camera connected to the Web continuously for an indefinite time, rather than for a particular session, generally supplying a view for anyone who visits its web page over the Internet. Some of them, for example, those used as online traffic cameras, are expensive, rugged professional video cameras.Windows To Go
Windows To Go is a feature in Windows 8 Enterprise, Windows 8.1 Enterprise, Windows 10 Education, Windows 10 Enterprise, and Windows 10 Pro (limited to "Education" or "Enterprise" image) that allows them to boot and run from certain USB mass storage devices such as USB flash drives and external hard disk drives which have been certified by Microsoft as compatible. It is a fully manageable corporate Windows environment.
It is intended to allow enterprise administrators to provide users with an imaged version of Windows that reflects the corporate desktop. Creation of Windows To Go drives is not officially supported by non-Enterprise (or Education) Windows 8.1 editions; however, Enterprise and Education versions of Windows 10 are supported. Some information has been published describing various ways to install Windows To Go using any version of Windows 8.x and 10 and any bootable USB device.
Interfaces are listed by their speed in the (roughly) ascending order, so the interface at the end of each section should be the fastest.
DC power delivery
|Not USB based|
|USB device classes|