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[ The PC Guide | Systems and Components Reference Guide | Hard Disk Drives | Hard Disk Interfaces and Configuration | Specialty and Future Hard Disk Interfaces ]

Universal Serial Bus 2 (USB 2.0)

After a slow start, the Universal Serial Bus (USB) is taking the PC world by storm. USB ports are showing up on all new PCs, and at the same time, a surprisingly wide array of USB peripherals is appearing on the market. However, the initial implementation of USB (version 1.1) has a critical restriction that limits its ability to function as an effective interface for high-speed devices, such as storage units: it is too slow. With a maximum bandwidth of 12 Mbits per second, conventional USB is already many times slower than what most optical and hard disks need, and that bandwidth must be shared amongst all peripherals using the interface.

Seeing the limitations of USB, Intel has spurred the development and implementation of USB 2.0, an updated version of the interface that increases throughput from 12 Mbits per second all the way up to 480 Mbits per second! USB 2.0 devices and systems will be both forward and backward compatible with USB 1.1 devices, which means that you will be able to mix both types of devices on systems that have either USB 1.1 or USB 2.0 host controllers. (Of course, systems without a USB 2.0 controller will only function at the slower 1.1 speed.)

You might wonder: why bother with this at all? Why not leave USB for slower devices, as it was originally intended, and use IEEE-1394 for high-speed devices, as it was intended? It's a good question. The answer is: that would make too much sense. :^) More seriously, one reason may be that USB has just been more widely-accepted in the PC world, and with USB 2.0 both backward and forward compatible with USB 1.1, hardware makers felt it made more sense to upgrade USB's capabilities. USB 2.0 may also be cheaper to implement. I suspect that the driving reason, however, is "more of the same" in terms of big companies clashing for control over the market: Apple Computer owns the FireWire name and has royalty rights on IEEE-1394, and Intel probably doesn't want to "play the game with Apple's ball", if you know what I mean. Just my personal suspicions, but this has happened many times before in the world of computers...

So will USB 2.0 become the next standard, or will IEEE-1394 finally gain acceptance in the PC world? Your guess is as good as mine. :^) As for our area of prime concern here, storage devices, USB 2.0 is a big win. While the fastest hard disks will eventually saturate 480 Mbits/second, it will be many years before USB 2.0's bandwidth comes even close to being a big issue, while USB 1.1 is today. With USB 2.0, serially-connected, high-speed hard disks and optical drives will be a practical reality. Look for USB 2.0 to hit the shelves early in 2001, barring any major complications in development (which are always a possibility...)

Note: For more information on USB 2.0, see the USB Implementers Forum site.


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