loaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Premises Technologies Premises Technologies Input/Output (I/O) Devices I/O devices are those that provide an interface between the user and the computer and include mice, keyboards, monitors, printers, scanners, modems, speakers, and any other devices that take data in or spit data out of the computer. The Bus Interconnecting the components of the computer is a cable known as a parallel bus. It is called "parallel" because the bits that make up one or more eight-bit bytes travel down the bus beside each other on individual conductors, rather than one after the next as occurs in a serial cable on a single conductor. Both are shown schematically in Figure 5-7. The advantage of a parallel bus is speed: By pumping multiple bits into a device in the computer simultaneously, the device-such as a CPU-can process them faster. Obviously, the more leads there are in the bus, the more bits can be transported. It should come as no surprise, then, that another differentiator of computers today is the width of the bus. A 32-bit bus is four times faster than an eight-bit bus; as long as the internal device to which the bus is transporting data has as many input/output leads as the bus, it can handle the higher volume of traffic. The parallel Figure 5-7 Parallel and serial buses Parallel Bus 01110011 Serial Bus Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Premises Technologies Chapter 5 bus does not have to be a flexible gray cable; for those devices that are physically attached to the main printed circuit board (often called the "motherboard"), the parallel bus is extended as wire leads that are etched into the surface of the motherboard.