The next generation of USB  – USB 3.0 or USB Superspeed

The Universal Serial Bus (USB) was ranked as our top PC innovation of all time by MaximumPC and it is in everyday use by millions around the World. But what do you need to know about the next version of USB?

USB 2.0 (otherwise known as USB Hi-Speed) boosted the original 12Mbps data rate to 480Mmb/s over 8 years ago, and now USB 3.0 (or USB Superspeed) is set to multiply that bandwidth 10 times.

USB 3.0 will be backwards-compatible with USB 2.0
Like the upgrade from USB 1.1 to 2.0, the new 3.0 connectors and cables will be physically and functionally compatible with hardware from the older specs. You will be able to maximize your bandwidth only if  using a USB 3.0 cable with Superspeed devices and ports, but at least plugging a 3.0 cable into a 2.0 port won’t blow up your PC. The spec’s compatibility lies in the design of the new connectors. USB 2.0 cables worked off of four lines – a pair for in/out data transfer, one line for power, and the last for grounding. USB 3.0 adds five new lines (the cable is thicker), but the new contacts sit parallel to the old ones on a different plane, as opposed to being adjacent to them. This means you’ll be able to differentiate between 2.0 and 3.0 cables just by looking at the ends.
The maximum speed of USB 3.0 is 4.8Gbps
It’s true: USB 3.0 SuperSpeed will be 10 times faster than the 480Mbps limit of the 2.0 spec.  You are only going to be able to take advantage of this speed if your USB portable storage device can write data that quickly. Solid state devices will benefit most from the speed boost, while magnetic hard disks will be limited by their RPM and corresponding read/write speeds. Also, new Mass Storage Device drivers will have to be developed for Windows to take advantage of the spec.

Uploads and downloads are kept on separate data lanes
Remember those five new lanes we mentioned earlier? With USB 3.0, two new lanes will be dedicated to transmit data, while another pair will handle receiving data. This not only accounts for the significant speed boost, but also allows USB 3.0 to both read and write at the same time from your portable storage device. In the old spec, the pair of lanes used for data transfer weren’t split between send and receive – they only could handle traffic in one direction. Bi-directional data transfer will be very useful for syncing up information on PDAs and storage backup.

USB 3.0 will charge more devices, quicker
Not only will USB 3.0 cables facilitate faster transfer speeds, but they’ll carry more power, too. The USB-IF recognizes the growing number of portable devices that charge via USB (mobile phones, MP3 players, digital cameras), and have bumped the power output from about 100miliamps to 900 milliamps. That means not only will you be able to power more than 4 devices from a single hub, but the increase current will let you charge up heftier hardware as well.

USB 3.0 will be more power efficient
One of the mandates of the new spec is more efficient power-usage protocols. USB 3.0 abandons device polling in favor of a new interrupt-driven protocol, which means non-active or idle devices (which aren’t being charged by the USB port) won’t have their power drained by the host controller as it looks for active data traffic. Instead, the devices will send the host a signal to begin data transfer. This feature will also be backward compatible with USB 2.0 certified devices.

USB 3.0 devices are expected to be avaialble late 2009 or early 2010.
However, it is expected that it would probably be able to achieve half of the theoretical value and to some ir seems that such expectation is still too high, at least for the initial products. The initial USB 3.0 prototype being demoed at CES 2009 event held in Las Vegas is only capable to achieve maximum of 1320Mbps, which is merely a quarter of what being promised earlier by USB 3.0 specifications.

To be more precise, the read operation of the USB 3.0 can only achieve 1320 Mbps while the write operation stays around 1000Mbps. This could be understandable since the demo product is a very early stage prototype model but the USB-IF personnel did emphasize that even there should be some bandwidth improvements with design optimization before the end commercial products being made available by end of 2009 time frame, but we shouldn’t be too optimistic to be able to enjoy 10 times faster transmission speed as compared to existing USB 2.0 specifications.

This scenario is similar to when we started to adopt USB 2.0 since few years back that will have to go through evolution cycle with significant design effort and resource investment before a much more stable and mature end product can be realized.

So keep your USB devices busy and stay on the look-out for the next generation.

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