The Architecture and features of USB 3.0

The USB 3.0 was first designed in 2008. USB stands for Universal Serial Bus. The USB 3.0 has come with 10 times higher transfer rate than USB 2.0. The USB 3.0 is also called as Super Speed USB. Its transfer rate is 5 Gbit/S. In this design, many improvements have been achieved. Earlier concepts of four transfer types (such as control, bulk, interrupt, and isochronous) are preserved in this version; but the electrical interface and the protocol are different from USB 2.0.

Logo USB 3.0 — By “en.wikipedia.org”

Due to the changes improvements have been done in the following areas – transfer speed, bandwidth, power management, bus utilization, and rotating media. In the USB 3.0 two unidirectional data-paths have been used, one is for receiving data and one for transmitting. Improved bus utilization is a new feature to the USB 3.0; this feature allows a device to notify (asynchronously) the host about its readiness. An updated bulk protocol (Bulk is a reliable transfer which includes a handshake process) which is called as Stream Protocol has been used in USB 3.0. Data transmission time and power consumption can be reduced by using the USB 3.0. Due to the dual-bus architecture in USB 3.0 both the USB 0 and USB 3.0 operations can be taken place simultaneously.

The 10 times faster speed has been achieved by adding the second physical data-path which is operated with the USB 2.0 data-bus in parallel. Five extra wires have been added to the cable. One pair is for transmitting, one pair is for receiving, and one wire is used for ground. Dual-simplex-data-transfer is utilized in USB 3.0. As separate pairs are used for transmitting and receiving, the effective throughput of USB 3.0 is twenty times higher than the USB 2.0 when receiving and transmitting data.

Another significant improvement has been done on USB 3.0 in power efficiency. Many power-hungry peripherals need a separate power connection though there is a connection of USB 2.0. Only 100 mA (in low-power state) can be provided by the USB 2.0; whereas the USB 3.0 can provide 150 mA. In case of configured devices, 500 mA can be supplied by the USB 2.0, and 900 mA can be provided by the USB 3.0. Using the USB 3.0 bus power one can charge the power-hungry devices quickly.

Considerable power savings can be done with the interrupt-driven protocol which has replaced the continuous polling feature of the USB 2.0. In the continuous polling feature, each connected peripheral is continuously polled by the host if the peripheral has any data for transmitting to the host. An example can make it easier. Think that a printer and a hard drive are connected to the computer, if they are connected via the USB 2.0 then data will be sent to both of the devices, if they are connected via the USB 3.0 then data will be sent only to the device which needs it. Uses of USB 3.0 are being increased. In the year of 2011 alone, over 70 million chips have been shipped.

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Author: SalimuddinSultan

Syed Ahmed Salimuddin Sultan is a Computer Science graduate. He has written many technical articles on different sites.
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