Hardware Reference
In-Depth Information
used by native USB 2.0 devices. A USB 3.0 hub supports 5Gbps (SuperSpeed) devices as
well as any slower USB 2.0 and 1.1 devices.
The maximum cable length between two USB 2.0 480Mbps (Hi-Speed) or USB 1.1
12Mbps (Full-Speed) devices, or between a device and a hub, is 5 meters using twisted-
pair shielded cable with 20-gauge wire. The maximum cable length for USB 3.0 Super-
Speed (5Gbps) connections, as well as any Low-Speed (1.5Mbps) devices using non-
twisted-pair wire, is 3 meters. These distance limits are shorter if smaller gauge wire is
used (see
Table 14.1
).
Table 14.1 Maximum Cable Lengths Versus Wire Gauge
USB 2.0
USB 2.0
(also called
Hi-Speed USB
) is a backward-compatible extension of the USB 1.1
specification that uses the same cables, connectors, and software interfaces but that runs
40 times faster than the original 1.0 and 1.1 versions. The higher speed enables higher-
performanceperipherals(suchasstoragedrives,higher-resolutionweb/videoconferencing
cameras, scanners, and faster printers) to be connected externally with the same easy PnP
installationforwhichUSBhasalwaysbeenknown.Fromtheend-userpointofview,USB
2.0 works the same as 1.1—only faster. All existing USB 1.1 devices work in a USB 2.0
busbecauseUSB2.0supportsalltheslower-speedconnections.USBdataratesareshown
in
Table 14.2
.
Table 14.2 USB Data Rates
