USB 2.0 and USB 1.1 differ only in speed and some minor changes in the data transfer protocol for the mode Hi-speed (480Mb/sec) of USB 2.0. There are three speeds of USB 2.0 devices operation:
- Low-speed 10—1500 Kb/sec (is used for interactive facilities: keyboards, mouses and joysticks)
- Full-speed 0.5—12 Mb/sec (audio-/video-devices)
- Hi-speed 25—480 Mb/sec (video-devices and data storage devices)
In fact, although in theory the USB 2.0 can reach 480 Mb/sec, in reality the devices of the hard drive type and any other information carriers never reach such a transfer rate, though they can make it. This can be accounted for by comparatively high delays of the USB between the request to transfer data and the transfer start itself. For example, the other bus, the FireWire, although it provides the maximum speed of 400 Mb/sec, which is by 80 Mb/sec less than that provided by the USB, in reality allows to a reach higher transfer rate with the hard drive and other data storage devices.