Dell Inspiron 5720, Owner'S Manual, Page: 78 / 113

USB features
The Universal Serial Bus, or well known as USB was introduced to the PC world in 1996 which dramatically simplified the connection
between host computer and peripheral devices such as mice and keyboards, external hard drive or optical devices, Bluetooth and many
more peripheral devices in the market.
Let's take a quick look on the USB evolution referencing to the table below.
Table 4. USB evolution
Type Data Transfer Rate Category Introduction Year
USB 3.0 5 Gbps Super Speed 2010
USB 2.0 480 Mbps High Speed 2000
USB 1.1 12 Mbps Full Speed 1998
USB 1.0 1.5 Mbps Low Speed 1996
USB 3.0 (SuperSpeed USB)
For years, the USB 2.0 has been firmly entrenched as the de facto interface standard in the PC world with about 6 billion devices sold, and
yet the need for more speed grows by ever faster computing hardware and ever greater bandwidth demands. The USB 3.0 finally has the
answer to the consumers' demands with a theoretically 10 times faster than its predecessor. In a nutshell, USB 3.0 features are as follows:
• Higher transfer rates (up to 5 Gbps)
• Increased maximum bus power and increased device current draw to better accommodate power-hungry devices
• New power management features
• Full-duplex data transfers and support for new transfer types
• Backward USB 2.0 compatibility
• New connectors and cable
The topics below cover some of the most commonly asked questions regarding USB 3.0.
Speed
Currently, there are 3 speed modes defined by the latest USB 3.0 specification. They are Super-Speed, Hi-Speed and Full-Speed. The new
SuperSpeed mode has a transfer rate of 4.8Gbps. While the specification retains Hi-Speed, and Full-Speed USB mode, commonly known
as USB 2.0 and 1.1 respectively, the slower modes still operate at 480Mbps and 12Mbps respectively and are kept to maintain backward
compatibility.
USB 3.0 achieves the much higher performance by the technical changes below:
• An additional physical bus that is added in parallel with the existing USB 2.0 bus (refer to the picture below).
• USB 2.0 previously had four wires (power, ground, and a pair for differential data); USB 3.0 adds four more for two pairs of differential
signals (receive and transmit) for a combined total of eight connections in the connectors and cabling.
78 Technology and components