Hardware Reference
In-Depth Information
USB conforms to Intel's PnP specification, including hot-plugging , which means that you
can plug in devices dynamically without powering down or rebooting the system. Simply
plug in the device, and the USB controller in the PC detects the device and automatically
determines and allocates the required resources and drivers. One advantage of an inter-
face such as USB with older systems is that it requires only a single IRQ from the system.
Therefore, youcan connect upto 127devices, and they will not use separate IRQs as they
might if each was connected over a separate interface.
USB 3.0 (SuperSpeed USB)
USB 3.0 (also called SuperSpeed USB) offers performance and bandwidth that is more
than 10 times the performance of USB 2.0 and yet is backward compatible with existing
USB1.1and2.0.Inaddition,USB3.0isoptimized forlowerpowerconsumptionandim-
proved protocol efficiency (less overhead).
On September 18, 2007, Intel announced both the formation of the USB 3.0 Promoter
Group and the development of the USB 3.0 interface, which had already been well un-
derway. The initial members of the group included Intel, HP, Microsoft, NEC, NXP, and
Texas Instruments. The final USB 3.0 specification was released on November 17, 2008.
The main feature of USB 3.0 is an increased transfer speed of 5Gbps (500MBps), thus
significantly reducing the time it takes to move data. Table 14.6 shows the time it takes
each version of USB to transfer the amount of data contained in popular media, includ-
ing a music CD ripped as 320Kbps MP3 files, a standard definition movie, and a high
definition movie. These numbers point to the actual or effective transfer rates of USB, ac-
counting for protocol overhead. From these numbers, you can see that USB 2.0 is about
40 times faster than USB 1.1, and USB 3.0 is more than 10 times faster than USB 2.0. An
Search WWH ::




Custom Search