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USB 3.0: What Is It?

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After ten years, the faithful USB 2.0 connection standard is beginning to look a bit long in the tooth. Thankfully we've finally been given its successor, and it's a scorcher. USB 3.0 is theoretically up to 10 times faster than its predecessor, and adds quite a few other improvements too. So let's see what it's all about.

Universal Serial Bus (USB) is the connector used by most modern electronic devices (everything from your computer to your camera, console and mobile phone) to exchange data, connect peripherals, or even to charge devices. It's a universal standard with rugged connectors, and carries not only data but power too, often avoiding the need for separate power sources. However, since the original USB's maximum speed of 12Mbit/s is too low for many common devices, it was revised to 480Mbit/s in the fully backwards-compatible USB 2.0, also known as high-speed USB. This improved things greatly and made USB adequate for the vast majority of devices, but anyone who's had to wait hours while backing up the contents of their computer to an external hard drive will know there's still plenty of room for improvement.

The solution, as decided by the USB Implementers Forum, is USB 3.0 (also known as 'SuperSpeed USB'). It ups its predecessor's theoretical maximum bandwidth from 480Mbit/s to 4.8Gbit/s (4,800Mbit/s) as well as increasing maximum power draw from 500mA to 900mA. It's now also fully duplex, meaning that data can travel both up and down the link simultaneously. This all adds up to a far more powerful and flexible connector that can turn its hand to just about any general connectivity task required (bar perhaps getting the most from the fastest SSDs in the future).

Unfortunately real speeds are rarely as fast as theoretical maximums, due to all sorts of reasons including physical limitations (like poor cabling), data packet and transfer protocol overheads, and the simple fact that multiple devices may be communicating over the same connection. In our review of the Buffalo DriveStation HD-HXU3 external hard drive, we found that USB 3.0 provided a minimum of three times the performance of its predecessor while at best it gave 5.4 times the speed. This may seem poor compared to the x10 performance increase suggested by theoretical numbers but it's still nothing to sniff at and is mainly held back by the 'slow' moving-parts hard drive (a fast SSD will do a better job of showing off USB 3.0's speed), not to mention that these figures will only get better as controllers, drivers, and hardware improve.


Results from our Buffalo DriveStation HD-HXU3 tests

When it comes to backwards compatibility, you can easily plug USB 2.0 devices into USB 3.0 controller ports as they're exactly the same shape and size, differentiated only by their blue rather than black colour – so when USB 3.0 becomes universal you will still be able to use all your favourite stuff. Obviously, you can also plug USB 3.0 devices into older ports so you could, for instance, plug your new USB 3.0 storage device into your mate's old computer to swap some files, but it will of course be limited to the speed of the older standard.

The original USB 2.0 ports are on the left, with blue-liveried USB 3.0 ports on the right

To avoid confusion, USB 3.0 cables are not only differentiated by carrying blue colour-coding on the sockets, but also by featuring a completely new and uniquely-shaped connector at the device end. So to sum up, you can plug USB 2.0 and 3.0 devices into any socket that will fit them, but to take advantage of USB 3.0's superior speed and other characteristics you need to plug blue connectors into blue sockets.

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