Everything You Wanted to Know About USB 3.0

The USB technology has come a long way since 1995, when USB 1.0 could only transfer 12 Megabits per second, and Windows NT lacked support for the new “standard.” It was only when USB 2.0 showed up in 2000, with its 480Mbps data transfer, that the days were numbered for other interfaces, including PS/2, serial, parallel, and even FireWire. Today, USB 3.0, also known as SuperSpeed USB, with its 5 Gigabits per second (Gbps), is finally catching on.

The improvement isn’t only in the standard’s version number. USB 3.0’s “SuperSpeed” 5Gbps is more than ten times faster than USB 2.0’s top theoretical speed of 480 Mbps. USB 3.0 supports asynchronous data transfers, which means that (unlike USB 2.0) it doesn't need to wait to poll a USB device every time it ships data one way or the other.

In addition, USB 3.0 includes a new transfer method called bulk streams, which lets USB support multiple data stream transfers. The net effect is that the protocol does much better with huge data transfers. Such as, say, if you’re viewing an high-definition movie that resides on an external hard drive.
USB 3.0 has more than just pure speed going for it. USB 3.0, like the other USB standards before it, lets you power up devices. USB 3.0, however, takes external power management to a whole new level.

First, USB 3.0 supplies 50% more power to devices. With this you can power not just thumb drives but also external drives like hard and CD/DVD drives. As lightweight laptops drop optical drives, that last advantage may become increasingly important.

Second, the USB 3.0 standard uses interrupts now instead of polling when a device is plugged in. With polling, when you plug in a USB device, your PC keeps constantly checking to see if needs anything, like a sometimes over-friendly waitress. Polling can keep the computer from going into low power states and can quickly drain a battery. Even a plain-old USB mouse can do this. That's bad news on a laptop. By using interrupts, USB 3.0 doesn't waste time or energy on an idle device. This can really save you some battery life.

Source: HP
By: Steven Vaughan-Nichols