Steve Smith explains why the Universal Serial Bus is so useful, and why it is backwards compatible.
Episode #4-39 released on June 12, 2014
The Universal Serial Bus, USB for short, has been an industry standard since the 1990s, and has defined which types of cables we all use for all of our devices. Starting with the USB 1.x running at a mere 12 Mbit/s for USB 1.0 at full bandwidth. While this may not be fast by our modern standards, this is plenty fast for the applications we used in those days.
Now the reason why we use USB to this day, is because in April 2000, USB 2.0 was introduced with a maximum signal rate of 480Mbit/s a lot faster than USB 1.x standards. And we have been using this technology freely without cause for over 8 years without any issues what so ever. All of our phones and mobile devices charge using USB now, most of us use USB flash drives, and USB based portable hard drives. Most peripherals use the modern USB interface, and even main boards come with a dozen or more USB ports on them. However, transferring large files via USB 2.0 is time consuming and in this fast paced world, time is a very limited part of life.
In an effort to spend less time transferring files, and to avoid having consumers and developers change interface completely, a new USB standard had to be made, in November of 2008, USB 3.0 was released onto the world to delivering speeds 10 times faster than USB 2.0, a full 4800Mbit/s. This means we spend a tenth of the time transferring files compared to before.
Now, what makes USB special, especially the fact that both the 2.0 and 3.0 can inter-operate, is the way they were designed. USB 2.0 receptacles and devices use 4 traces, where as USB 3.0 has 9 traces. However, the 4 normal USB 2.0 style traces exist in both technologies making most peripherals capable of running on both. Better yet, a USB 3.0 extension cable can support a USB 2.0 device, and vice versa.
Now, if we can use both USB 2.0 and USB 3.0 cables and devices together, how can we tell them apart? For one, USB 3.0 devices and cables are usually colored blue in the connector. Apart from the Type A connector, all other USB 3.0 connectors are very different from their USB 2.0 counterparts, without making them unusable. A USB 2.0 cable will plug into a USB 3.0 device jack, but a USB 3.0 cable, not counting the TYPE A connector, will not fit into a USB 2.0 device. This makes errors less frequent and makes it easier to tell apart.
Basically, like my PCI Express video, everything basically works together, and is intentionally compatible, unless the device has a very specific power requirement. However, this is limited to USB 3.0 portable drives, and you can always get a Y-split cable.
Host : Steve Smith | Music : Jonny Lee Hart | Editor : Steve Smith | Producer : Zed Axis Productions