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
Token/Data/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