April 06, 2010, 9:46 PM — When you're in front of your PC, waiting for something to transfer to removable media, seconds can feel like minutes, and minutes like hours. And backups to USB 2.0 appear to crawl along at a snail's pace--so much so that users often become reluctant to perform that essential chore.
Such data-transfer scenarios are where the new SuperSpeed USB 3.0 standard and its theoretical, blazing-fast throughput of 5 gigabits per second--as promised by the USB Implementers Forum (USB-IF)--will change your life for the better. And if our tests of four new USB 3.0 hard drives from Buffalo Technology, Iomega, Seagate, and Western Digital are indicative, the change will be dramatic.
USB 3.0's impressive speed is its raison d'être, but part of its beauty is its backward compatibility with USB 2.0. You need a new cable and a new host adapter (or one of the new motherboards built to support USB 3.0) to achieve USB 3.0 performance. But you can still use a USB 3.0 device on a USB 2.0 port and achieve typical USB 2.0 performance. You may also use USB 2.0 devices on a USB 3.0 port--though, again, with no gain in speed.
The technology behind USB 3.0 more closely resembles PCI Express than USB 2.0. Backward compatibility comes from clever connector design, and a dual bus. The designers added four data lines and a ground wire for the new USB 3.0 signals, and retained the existing pair of data lines for use with USB 2.0 devices. The two technologies share the existing power and ground wires, but they are otherwise completely separated.
As such, the USB 3.0 connector has design changes to accommodate the extra data lines. If you examine the inside of a type A USB 3.0 port with its familiar rectangular shape closely, you'll see that it shares the same size as a USB 2.0 port as well as the original four USB 1.1/2.0 contacts.
However, the port also has an additional five smaller contacts for the new USB 3.0 lines. When you plug in a 2.0 connector, it uses the four original contacts; when you plug in a USB 3.0 connector, it taps into the other five. Because motherboards and PCs will ship with both USB 2.0 and USB 3.0 ports, their insulating plastic, by specification (to distinguish them) must be bright blue on USB 3.0 ports, but black on USB 2.0 ports. Similar tricks have been used for the type B and mini connectors.
Another potential benefit of USB 3.0: The spec calls for a mere one-third of the power consumption USB 2.0 uses. The creators achieved that by reducing some of the background maintenance requirements of USB; unlike before, with USB 3.0 the interface transmits data only to the link and device that need that info, which allows other attached devices to go into a low-power state when not needed. The change applies only to the USB bus, not to the power that USB peripherals require or use for their own operation-although getting things done faster ultimately means using less power, as well.