Universal Serial Bus (USB) is an input/output port standard for computers and digital equipment, which allows easy transfer of data via a direct connection or cable. The original USB standard version has been superceded by hi-speed versions. A hi-speed USB host controller refers to the hardware inside the computer that provides hi-speed USB functionality to the ports.
USB first hit the market in November 1995, but the new standard had compatibility problems. These bugs were addressed and the subsequent USB version is now referred to as “original” USB 1.1. The data transfer rate (DTR) for USB 1.1 was impressive at 12 megabits per second (mbps), and it was intended to replace slower parallel and serial ports for peripheral devices. The first devices to be widely adopted for USB ports were keyboards and mice. Printers, scanners, external tape drives and other devices followed.
As demands for faster data transfer increased, a newer version of USB answered the call. USB 2.0 boasts maximum data rates of 480 mbps, 40x faster than original USB. Computers that supported the old standard required a new hi-speed USB host controller to take advantage of the faster speeds. Devices made for the new 2.0 standard, such as memory sticks and digital cameras, would default to the old, slower transfer speeds if plugged into a computer with a USB 1.1 controller installed.
A hi-speed controller is built into modern computers, while older computers can be updated with the hardware. A controller is inexpensive and can be purchased anywhere computers are sold. It is a card that easily installs into any available slot in the motherboard. The back-facing plate of the controller provides two or more hi-speed USB ports.
To take advantage of USB 2.0 speeds, both the computer and the device plugged into the USB port must both support the 2.0 standard. A hi-speed USB host controller cannot make a USB 1.1 device operate at 2.0 speeds. Hi-speed controllers are backward compatible, however, falling back to the slower 1.1 standard for devices that require it.
One of the many advantages of USB ports is that they can operate in a daisy chain, and one controller can control several USB ports. If a computer doesn’t have enough ports for the user's needs, a USB hub can be added. The hub plugs into a single USB port while offering a “bay” of additional ports. Some devices might require a direct port or a powered hub, however. Powered hubs have their own A/C adapters.