by Bruce Tyson

Created on: January 13, 2010   Last Updated: January 14, 2010

USB keyboards are the latest iteration of the PC keyboard, recently supplanting the dominance of the PS2. Some people believe that the USB keyboard is better than the older types while others may question whether the USB keyboard has any advantages at all. These questions as well as the questions arising from relevant terminology need to be answered in order to determine if the USB keyboard is at all superior to a “serial keyboard.”

Because every style of PC keyboard interface uses serial communications with the keyboard controller, they are all technically serial devices with the primary differentiation between the several types of keyboards being the connectors they use. The XT and AT style keyboards connect to the computer with a 5 pin DIN, while PS2 style keyboards connect with a 6 pin mini DIN. USB style keyboards connect with a standard USB connector.

In the vernacular, the term "serial keyboard" usually refers to an AT style keyboard, rather than to a keyboard that connects to a serial port on a computer. Although true serial keyboards do exist, they are rare in the PC world, being primarily associated with microcontrollers, TTY, and other devices. The etymology of the term is traceable to the era when the PS2 mouse was replacing the serial mouse and the PS2 keyboard was also coming into vogue. Everyone knew that the PS2 mouse was replacing the serial mouse, but people were unsure what to call the keyboard that was being replaced by the PS2 keyboard. Because of this uncertainty, an analogy developed: "A PS2 mouse is to a serial mouse as a PS2 keyboard is to a serial keyboard." This misnomer was widespread during the period, but has largely died out in conjunction with the demise of AT form factor computers.

For the purpose of this article, a "serial keyboard” is considered to be a keyboard with either an AT or PS2 connector. Here are a few criteria that help decide whether or not the USB keyboard is better than the others.

= User Interface =

Because USB keyboards function the same way as the PS2 and AT keyboards, computer users will not find any advantage to either type.

= Hot swapping =

USB keyboards are hot swappable. This means that the keyboard can be plugged in or removed at any time while the computer is running and will still work. While AT keyboards can be plugged in and removed at will most of the time, doing this sometimes causes a current spike on the motherboard, blowing the fuse that protects the keyboard circuit.

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