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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.
To allow for voltage drops, the voltage at the host port, hub port, and device are specified to be at least 4.75 V, 4.4 V, and 4.35 V respectively by USB 2.0 for low-power devices, [a] but must be at least 4.75 V at all locations for high-power [b] devices (however, high-power devices are required to operate as a low-powered device so that they ...
12 V and 24 V powered USB sockets, on an NCR cash register. PoweredUSB, also known as Retail USB, USB PlusPower, USB +Power, and USB Power Plus, [1] is an addition to the Universal Serial Bus standard that allows for higher-power devices to obtain power through their USB host instead of requiring an independent power supply or external AC adapter.
All USB hubs can operate at this rate. High speed (HS) rate of 480 Mbit/s was introduced in 2001 by USB 2.0. High-speed devices must also be capable of falling-back to full-speed as well, making high-speed devices backward compatible with USB 1.1 hosts. Connectors are identical for USB 2.0 and USB 1.x.
Power equals voltage times current. A USB port that draws 500 mA (0.5 A) at 5 volts is drawing 2.5 watts of power. In Bus-powered USB hubs, each USB port can supply power as well as transfer data. A self-powered hub takes its power from an external power supply unit and can therefore provide full power (up to 500 mA) to every port. Self-powered ...
eSATAp throughput is not necessarily the same as SATA, many enclosures and docks that support both eSATA and USB use combo bridge chips which can severely reduce the throughput, and USB throughput is that of the USB version supported by the port (typically USB 3.0 or 2.0). eSATAp ports (bracket versions [clarification needed]) can run at a ...
USB 3.0 SuperSpeed and USB 2.0 High-Speed versions defined USB 3.0 SuperSpeed – host controller (xHCI) hardware support, no software overhead for out-of-order commands; USB 2.0 High-speed – enables command queuing in USB 2.0 drives; Streams were added to the USB 3.0 SuperSpeed protocol for supporting UAS out-of-order completions USB 3.0 ...
For example, a USB 2 PCIe host controller card that presents 4 USB "Standard A" connectors typically presents one 4-port EHCI and two 2-port OHCI controllers to system software. When a high-speed USB device is attached to any of the 4 connectors, the device is managed through one of the 4 root hub ports of the EHCI controller.