USB (Universal Serial Bus)

USB is a bus that is designed to be simple for end users. USB supports hot swapping devices, so it is possible to add and remove devices without rebooting the system. There are 3 major versions of USB (1.0, 1.1 and 2.0), operating at 3 different speeds (1.5 Mbps, 12 Mbps, and 480 Mbps). Virtually all USB ports on computers that have shipped in the past year or two are USB 2.0. All versions of USB are backward compatible, so a USB 1.1 device can plug into a USB 2.0 port without any problem.

What devices are available for USB?

Most peripherials that are available today for computer use are available in a USB version. This includes printers, scanners, keyboards, mice, network adapters, wireless adapters, etc. While all these devices are available for USB, they may not be the best option. For instance, a USB network adapter can only support 12 Mbps or 480 Mbps (depending on the version) while a PCI network adapter can support speeds up to 1000 Mbps.

The various versions

USB 1.0

USB 1.0 supports transfer rates up to 1.5 Mbps. Very few computers have true USB 1.0 ports on them. Most USB 1 ports are actually USB 1.1.

USB 1.1

USB 1.1 supports transfer rates up to 12 Mbps.

USB 2.0

USB 2.0 is much faster, supporting up to 480 Mbps. In order to get these extreme speeds, however, both your computer and the USB device must support the 2.0 standard and be Hi-Speed compliant. USB 2.0 actually comes in three flavors:

• Low Speed (1.5 Mbps) - Legacy, the old USB 1.0 standard.

• Full Speed (12 Mpbs) - The actual "normal" speed of USB 2.0 (which is identical to the old USB 1.1 transfer speed). If a product says that it's USB 2.0 without specifying Hi-Speed, then it's probably just a "Full Speed" drive in disguise.

• Hi-Speed (480 Mbps) - The transfer speed that everyone talks about when they mention USB 2.0. Products that support Hi-Speed usually have the following label pasted somewhere on the box:
  

If you're in the market for an external hard drive or flash drive, make sure that it's Hi-Speed compliant.