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Left to right: USB 3.0 Standard-A (host) port (the five additional contacts for USB 3 visible on the underside of the tongue), VGA connector, DisplayPort connector, USB 2.0 Standard-A (host) port. Additional power for multiple ports on a laptop PC may be obtained in the following ways:
Standard USB hub ports can provide from the typical 500 mA/2.5 W of current, only 100 mA from non-hub ports. USB 3.0 and USB On-The-Go supply 1.8 A/9.0 W (for dedicated battery charging, 1.5 A/7.5 W full bandwidth or 900 mA/4.5 W high bandwidth), while FireWire can in theory supply up to 60 watts of power, although 10 to 20 watts is more typical.
The xHCI reduces the need for periodic device polling by allowing a USB 3.0 or later device to notify the host controller when it has data available to read, and moves the management of polling USB 2.0 and 1.1 devices that use interrupt transactions from the CPU-driven USB driver to the USB host controller.
USB Battery Charging (BC) defines a charging port, which may be a charging downstream port (CDP), with data, or a dedicated charging port (DCP), without data. Dedicated charging ports can be found on USB power adapters to run attached devices and battery packs. Charging ports on a host with both kinds will be labeled. [59]
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 host controller (xHCI) provides hardware support for streams
The written USB 3.0 specification was released by Intel and its partners in August 2008. The first USB 3.0 controller chips were sampled by NEC in May 2009, [4] and the first products using the USB 3.0 specification arrived in January 2010. [5] USB 3.0 connectors are generally backward compatible, but include new wiring and full-duplex operation.
USB OTG is a part of a supplement [2] to the Universal Serial Bus (USB) 2.0 specification originally agreed upon in late 2001 and later revised. [3] The latest version of the supplement also defines behavior for an Embedded Host which has targeted abilities and the same USB Standard-A port used by PCs.
Originally developed by the Personal Computer Memory Card International Association (), the ExpressCard standard is maintained by the USB Implementers Forum ().The host device supports PCI Express, USB 2.0 (including Hi-Speed), and USB 3.0 (SuperSpeed) [2] (ExpressCard 2.0 only) connectivity through the ExpressCard slot; cards can be designed to use any of these modes.