@codinghorror wrote:
Interesting, more detail here
http://www.usr.com/education/peripherals0.asp
USB 3.0 cables facilitate the faster transfer rates of 4.8Gbps as well as the additional power transfer of 900 mA by doubling the amount of wires within the cable from 4 in the 2.0 cables to 8 in the 3.0 cables. USB 2.0 cables transfer data at 480 Mbps and provide power up to 500 mA.
USB 3.0 cables also have different connectors (typically blue on the inside) as can be seen in the image below alongside the 2.0 counterpart connectors. This means that any device that uses the different connectors cannot use the 2.0 equivalent cables. In addition while the 2.0 B connectors physically fit into the 3.0 B ports the different wiring configuration does not allow proper data transfer. The A connectors still work properly so any 2.0 device with a 2.0 cable can be used with 3.0 ports or hubs.