Everyone is familiar with the term 'USB' right? We associate it with those little flat connectors we stick into the matching sockets on our computers, sometimes connecting cameras, othertimes USB 'sticks', 'pendrives', or hard drives, smart phones, or a range of other devices. Quite ubiquitous.
But, if you read the ads in the local flyers carefully, you will more and more frequently see references to 'USB 3.0'. What is this and why should you care..?
There's enough technical information out there to write several books on USB, but that's not where we're going today - we'll focus on just two or three aspects, such as the relative performance, and how to differentiate between USB 3 and older USB cables and devices.
A little history...
The first standard for USB was issued in January 1996, with data transfer rates of 1.5 Mbit per second and 12 Mbit/s in "Low Speed" and "Full Speed" modes respectively. The higher transfer rate was intended for devices such as disk drives which require high data transfer rates.
The USB 2.0 specification was accepted in 2001, and provided a substantial increase in the data rate, increasing it to 480 Mbit/s. (Megabits, not megabytes!)
Fast forward to today...
November 2008 saw the publication of the USB 3.0 standard. Besides a huge speed increase over USB 2.0 from 480 Mbit/s to 5 Gbit/s, the new standard also set out to reduce power consumption and increase power output while remaining backwards compatible with USB 2.0. The new high speed capability is known as 'Superspeed'.
There's an enormous amount of technical information available on this topic, but we will touch on just a few salient points here.... for example, how to tell which are USB 3 devices and which are not, and what we need to achieve these fast transfer speeds with the hardware we typically find in small offices or at home.
To achieve the high speed data transfer, one needs a USB 3 port on the computer as well as on the device itself. You can see from the image that the new cable is differentiated by the colour of the plastic insulator used inside the plug and receptacle, USB 3 being blue, and white being the older USB standard (though black is also commonly used). Don't confuse this colour with the colour of the cable itself though, as designer USB cables are available in many colours with no relation to the standards.
While the image does not show it as clearly as desired, USB 3 cables are also thicker then their older counterparts, due to there being more wires in the cable, and this may be reflected in a larger moulding around the plug as can be seen in the photograph.
Newer computers are likely to be fitted with both types of USB ports, but it's a good idea to confirm that before purchase, if fast data transfer is important to you. Some computers may also have yellow USB ports - these are 'always on' charging ports, and are not powered off when the computer is shut down - this is important to know, if a laptop is involved, as leaving USB devices plugged into one of these could silently drain the laptop battery, unless it was on mains power.
Older machines - desktops - that is, can probably be upgraded by adding an adapter card, such as this one. Do check the open slots in your PC before purchase, or have your local computer tech do that for you, before purchasing the adapter. Notice that the receptacle as seen on this adapter card also contains a blue plastic component, matching the colour of that in the plug. 
Besides the higher data rate, USB 3 also can deliver higher voltage to the external device, which is needed for high performance items like hard drives. This image shows a PCI Express card. The PCIe "bus" or circuitry on the motherboard can't on its own provide enough power to the card for high power devices such as disk drives, so there is a socket on the corner of the card for additional power from the PC's power system, unless the external drive has it's own dedicated power supply. (With older USB drives, you may have encountered a special Y cable, with 2 USB plugs, one having a red outer moulding, both of which have to be plugged into USB sockets on the computer - the regular plug in such cases carries data and power, and the red plug additional power in order to run the device without an external power supply. As mentioned earlier, because USB 3 is able to deliver more power, Y cables are unnecessary for the 2.5" hard drives commonly found in newer compact portable drive units.
So, we talked a little about the hardware, but what of software... which systems support USB 3?
Well, if you're running any version of Windows older than Windows 7 Service Pack 1, there are no built in USB 3.0 drivers for the adapter cards in those systems, such as Vista, XP or older, so you would want to make sure that the manufacturer of the adapter has a driver available for your version of Windows. For Linux users, Linux kernel version 2.6.31 released in September 2009, and upward, supports USB 3.0. For MAC fans, Apple at last announced USB 3.0 equipped laptops in June 2012.
Of course, you could still plug that USB 3.0 gadget into a USB 2.0 port, where it will operate at USB 2.0 speeds, until you have a faster port available.
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