Like its predecessor, USB 3.0 will offer backward compatibility.
USB 3.0 cables are now 9-wired, instead of the previous 4, and have modified connectors.
Dimensions remain the same. USB 3.0 functionalities are provided when the added signal lines become connected.

USB 3.0 connector

USB 3.0 connector

USB3.0 Standard-A Connector

USB3.0 Standard-A Connector

USB3.0 B Connector

USB3.0 B Connector

USB3.0 Micro-B Connector

USB3.0 Micro-B Connector

Backward Compatibility

The connector has been modified to maintain connectivity with existing USB devices and cables.

 

Backward Compatibility