USB 3.0
USB3.com - USB 3.0 SuperSpeed Product Site by USBGear.com
USB 3.0 SuperSpeed
Features and Highlights
* 5Gbit/s Bus Speed! There is some spec overhead but speeds of 4Gbits are achievable.
* Backwards compatibility with USB 2.0 hi-speed devices.
* The new 500MB/s speeds can only be achieved using a USB 3.0 Standard-B plug.
* Cable makeup: 2 wires for power and ground, 2 for Hi-Speed backward compatibility, 4 wires for the new Superspeed.
* Improved power efficiency! USB 3.0 has no device polling and lower active and idle power requirements.
USB 3.0 Specification Explained
USB 3.0 plugs will be backwards compatabile with USB 2.0 devices and plugs, respectively. However, a new receptacle has been created "USB 3.0 Standard-B" which can only accept a USB 3.0 Standard-B device plug.
A big difference between the SuperSpeed 3.0 spec and the 2.0 Hi-Speed spec is how it communicates with devices. The new USB 3.0 SuperSpeed creates a communication pipeline with host and each device or a "host-directed protocol". The older USB 2.0 Hi-Speed broadcasted packets to all devices.
The SuperSpeed USB 3.0 mode provided by the new specification happens over 2 pairs of wires using dual-simplex signaling. This is all in addition to the older backward compatabile wires. The cable consists of:
* Ground
* Power
* 2 x Hi-Speed
* 4 x SuperSpeed
Power Management Features:
* Idle
* Sleep
* Suspend
* Link
* Device
* Function
Diagrams of a USB 3.0 receptacle
Photo of a USB 3.0 cable
Notice it looks very similar to a USB 3.0 cable. That's because it will be backwards compatible with USB 2.0.
USB 2.0 vs USB 3.0 SuperSpeed cable comparison photo
The dual bus architecture of SuperSpeed was attained cleverly through a composite cable and connector design that built on top of the existing USB 2.0 specification.
Here is an excellent diagram showing the dual bus architecture of the new USB 3.0 SuperSpeed spec. You will notice it has similar components as USB 2.0, interconnects, devices, hosts. One thing to note is that operating simultaneously in SuperSpeed and Hi-Speed is not allowed. It is an either or scenario.
USB 3.0 SuperSpeed can handle more power over its cable. 50% more than USB 2.0 or 150mA. Also the amount of voltage a device is required to have has dropped from 4.4V to 4V.
Even though there are no limits to the length a USB 3.0 cable can be. It has been estimated to be 3 meters to maintain SuperSpeed data transfer rates.