HOW IT WORKS: USB
The story of one simple connection…
The Universal Serial Bus (USB) arrived on 6 May 1998, at Flint Center, Cupertino.
Specified by an Intel-led industry partnership, it had already appeared in a few PCs, but it was only when Apple – not a member of the group – unveiled the first-generation iMac, with the traditional interfaces abolished, that we knew USB was the future. USB 1.1, capable of speeds up to 12Mbps, was “the new generation of I/O”, announced Steve Jobs. Simple, he said. Elegant, he said. And he was basically right. Although, if he’d envisaged that 20 years later USB would cover two data protocols running over six physical connections in five speed classes, he might have used some different words. The iMac’s ports were USB Type-A, the now familiar rectangular receptacle with a plastic tab across the middle. Its mouse and keyboard had matching steel-sheathed plugs attached, while peripherals like disk drives and printers would come with square USB Type-B ports, connecting with an A-to-B cable that established a two-way data flow and a one-way power supply, from computer (host) to accessory (device).
Socket to me
USB 2.0, emerging in 2001, boosted transfer rates to 480Mbps, competing with FireWire 400, which Apple had added to the iMac DV for video transfer. Smaller accessories, like digital cameras, didn’t have room for the full-size Type-B socket, and some manufacturers had invented their own. Now there were two official solutions: the sharp-cornered trapezoid Mini-B, and Micro-B, so small and flat that mating the plug and socket without incident required the skills of a porcupine breeder.
What made USB so successful was that the spec covered more than just the physical connection and communication protocols. It defined device classes – printer, mass storage, communications (networking), human interface (keyboards and mice) – so that ‘class compliant’ products could identify themselves to the computer and start working, with no need to install software drivers except for esoteric features. This also meant Macs and Windows PCs could use the same USB devices.
Generation gain
Nearly a decade later, USB 3.0 – branded SuperSpeed and indicated by an SS logo and a blue insert in the Type-A port – multiplied transfer rates tenfold to 5Gbps. But with more pins required, Micro-B had to be upgraded to what looked like two plugs stuck together.