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

Features USB3.0 USB2.0
Data Rate SuperSpeed (5.0Gbps) additional low-Speed (1.5Mbps)
full-Speed (12Mbps)
high-Speed (480Mbps)
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

Characteristic SS HS/FS/LS
Bus Configuration Dual Simplex Unicast Bus Broadcast Half Duplex Bus
Transaction Configuration Data/Handshake
OUT Token is included in Data Packet
IN Token is replaced by Handshake
Burst Transfer Supported Unsupported
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.

Power Supplying Capability