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TekSpek USB
USB 3.0

USB 3.0

Date issued:

What is USB 3.0?

USB 3.0 is the latest iteration of the ubiquitous Universal Serial Bus (USB) specification. The standard, first introduced in 1996, has since become the de facto interface for a wide range of computing devices, covering everything from memory sticks to digital cameras and much, much more.

USB 3.0 is the newest revision and acts as a forward step from the common USB 2.0 interface by offering improvements across the board; including faster data transfer speeds, the ability to serve more power to devices, and support for a new set of low-power operating modes.

But how much of an improvement is it really? Let's get a little more granular.

High-speed stakes

USB 2.0, which dates back to the year 2000, was a result of an initiative led by Hewlett-Packard, Intel, Lucent, Microsoft, NEC, and Philips, and raised the data transfer rates of the USB interface up to the then-dizzy heights of 480 Mbit/s - or 35MB/s in real-world usage.

A decade has since passed, and with the recent boom in HD media and increasingly large file sizes, there's now a demand for faster transfer speeds on devices such as external hard-disks or USB memory sticks.

Whilst competing standards - eSATA and FireWire, for example - offer speedy alternatives of their own, USB 3.0 is odds-on to become the next high-speed mainstream solution. And with over a billion USB devices already in circulation, who could argue?

So how does the USB 3.0 specification build on the existing speed of 480 Mbit/s?

Getting slightly technical, the desired effect is achieved by using more wires to transmit data. A traditional USB 2.0 connector features four wires - power, ground and two for data - but USB 3.0 expands upon that with a further four wires used to achieve "SuperSpeed" data rates. The end result is a theoretical top speed of 5Gbit/s (that's Gigabits, not Megabits). And there's more than just added bandwidth on offer. Unlike USB 2.0, which can only transfer data in one direction at a time, USB 3.0 provides bi-directional transfers, and supporting devices use asynchronous notifications to prevent the need for device polling. Sounds complicated, but what you need to know is that the technology all adds up to create an up-to ten-fold performance boost.

Power to the cable

The added performance of USB 3.0 is always welcome, but there's more to the specification than just greater transfer speeds.

Another area that has been notably improved is power management. With USB 3.0, attached devices can draw up to 900mA of power, up from 500mA on USB 2.0. Why would you want more power? Well, there are a few good reasons; with USB 3.0 you'll be run more powerful devices without the need for an AC power adapter, and you should, in theory, be able to charge USB devices quicker, too.

And don't worry about consuming more power than you'll need, as the USB 3.0 improvements work both ways. In an effort to make the USB standard more efficient, version 3.0 ensures less power is consumed when the interface is idle using link-level power management, which ensures either the host computer or the device can enter a power-saving state.

What about my existing USB 2.0 peripherals?

USB 3.0 sounding good thus far? It gets better; the new standard is backward compatible with all your USB 2.0 devices.

Whilst USB 3.0 cables are slightly thicker (there are more wires within, remember) and longer at the tip, they'll slot into existing USB 2.0 ports and operate at standard USB 2.0 speeds.

Working the other way, USB 2.0 cables will also fit into USB 3.0 ports and run at standard USB 2.0 speeds.

In order to get SuperSpeed transfers, you'll need a USB 3.0 device attached to a USB 3.0 port. What's clever is that the backward compatibility is achieved by using a slightly elongated USB 3.0 connector, whose extra set of contacts only come into play when hooked up to a 3.0 interface.

As a rule, you'll always get USB 2.0 speeds from a 2.0 device. With a 3.0 device, you'll get SuperSpeed transfer rates only if both the host and the device support the standard; i.e. plug it into a USB 3.0 port and you're good to go.

Well, what are we waiting for?

USB 3.0 clearly has its merits, but the technology has been on the fringe of the market for months, and hasn't quite managed to break into the mainstream.

There appear to be a few stumbling blocks. At present, the major chipset manufacturers - Intel and AMD - have been reluctant to add native USB 3.0 functionality to their core logics. Costs are of course an issue, and the few boards currently offered with integrated USB 3.0 are provided the functionality by a third-party NEC controller.

NEC, importantly, is currently the only manufacturer to produce xHCI USB 3.0 host controllers. VIA, ASMedia and Fresco Logic are just some of the names expected to produce USB 3.0 controllers in the coming months, and the availability of more chips should drive competition and lower prices.

However, whilst the host controllers and USB 3.0 devices themselves start to become widely available in greater numbers, adoption by industry heavyweights such as Intel and AMD is likely to be the triggering factor and tipping point for mainstream adoption.

Unfortunately, it seems both Intel and AMD won't introduce USB 3.0 to their respective chipsets until perhaps 2011. Reports have suggested that Intel will wait until various standards - USB 3.0, SATA 6Gbps and PCIe 3.0 - have all matured before integrating them into a new chipset, but cynics also argue that Intel may be slowing the progress of USB 3.0 in favour of its own next-generation interface; Light Peak.

Last but not least, we need to remember that whilst USB 3.0 hardware is now available in the marketplace, users will need the software to support it. NEC provides drivers for its own SuperSpeed host controller, but today's popular operating systems - Microsoft's Windows 7 and Apple's Mac OS X - don't yet offer built-in support for the USB 3.0 standard. The open-source Linux kernel, meanwhile, has supported USB 3.0 since late 2009.


There's plenty to like about USB 3.0, and the technology provides obvious and immediate benefits to the user.

However, it will require an industry-wide push to break into the mainstream, and USB 3.0 may therefore struggle to become widespread until at least 2011.

Question is; can USB 3.0 capture the market before the next major interface comes along?