USB 3.0 adds a new transfer mode, SS (SuperSpeed), which provides a maximum transfer rate of 5 Gbps, more than 10 times faster than the existing HS (high-Speed) mode. USB 3.0 thus aims to support application media requiring fast and high-capacity transfers.
SS uses an independent pair of wires for IN and OUT. The faster transfer rate for SS mode is achieved by using a bus configuration different from previous USB specifications.
USB3.0 vs USB2.0
|Data Rate||SuperSpeed (5.0Gbps) additional||low-Speed (1.5Mbps)
|Data Signal||SS OUT Differential Signal: 1 Pair
SS IN Differential Signal: 1 Pair additional
|Differential Signal: 1 Pair|
|Connector Signals||4 wires: SuperSpeed
2 wires: DP/DM for USB 2.0
3 wires: Vbus/GNDx2
|2 wires: DP/DM for USB 2.0
2 wires: Vbus/GND
|Bus Protocol||No polling||Uses polling|
|Power Control||Configuration at multiple link levels||Suspend/Resume by Port|
|Power Supply to Bus||Max. 900 mA||Max. 500 mA|
Characteristics of SuperSpeed Transfers
|Bus Configuration||Dual Simplex Unicast Bus||Broadcast Half Duplex Bus|
OUT Token is included in Data Packet
IN Token is replaced by Handshake
|Start Token||Asynchronous Notification by Device||Polling by Host|
Power Supplying Capability
USB 3.0 also offers enhanced bus power.
USB can now carry a current of up to 900 mA/port, up from the previous 500 mA/port, providing a more stable power supply to the devices.