What are the major USB 3.0 improvements?
In a nutshell, USB 3.0 promises the following:
- Higher transfer rates (up to 4.8Gbps)
- Increased maximum bus power
- New power management features
- Full-duplex data transfers
- Support for new transfer types
- Backward USB 2.0 compatibility
- New connectors and cables
The enhancements to SuperSpeed USB are not just for higher data rates, but for improving the interaction between device and host computer. While the core architectural elements are inherited from before, several changes were made to support the dual bus arrangement, and several more are notable for how users can experience the improvement that USB 3.0 makes over USB 2.0:
More power when needed
- 50% more power is provided for unconfigured or suspended devices (150 mA up from 100 mA), and 80% more power is available for configured devices (900 mA up from 500 mA). This means that more power-hungry devices, such as a 22" monitor or speedy portable drive, could be bus powered, and battery powered devices that previously charged using bus power could potentially charge more quickly.
- A new Powered-B receptable is defined with two extra contacts that enable a devices to provide up to 1000 mA to another device, such as a Wireless USB adapter. This eliminates the need for a power supply to accompany the wireless adapter...coming just a bit closer to the ideal system of a wireless link without wires (not even for power). In regular wired USB connections to a host or hub, these 2 extra contacts are not used.
Less power when it's not needed
Power efficiency was a key objective in the move to USB 3.0. Some examples of more efficient use of power are:
- Link level power management, which means either the host computer or the device can initiate a power savings state when idle
- The ability for links to enter progressively lower power management states when the link partners are idle
- Continuous device polling is eliminated
- Broadcast packet transmission through hubs is eliminated
- Device and individual function level suspend capabilities allow devices to remove power from all, or portions of their circuitry not in use
- Streaming for bulk transfers is supported for faster performance
- Isochronous transfers allows devices to enter low power link states between service intervals
- Devices can communicate new information such as their latency tolerance to the host, which allows better power performance