 Devices, such as I/O cards, attach to the board via edge connectors. Enough about computer internals. A brief word about computer his- tory and evolution is now in order. The work performed by Von Neumann and his contemporaries led to the development of the modern mainframe computer (Figure 5-8) in the 1960s and its many succeeding machine design generations. Targeted primarily at corporate applications, the mainframe continues to provide computing services required by most corporations: access to enormous databases, security, and support for hundreds of simultaneous users. These systems host enormous disk pools (Figure 5-9) and tape libraries (Figure 5-10), and are housed in self- contained windowless computer centers. Their components are intercon- nected by large cables that require they be installed on raised floor (Figure 5-11). They produce SO much heat that they are fed enormous amounts of chilled air and water and require constant attention and monitoring. It makes sense: These are very powerful creatures. Over time, computer technology advanced, and soon a new need arose. Mainframes were fine for the computing requirements of large, homoge- neous user communities, but as the technology became cheaper and more ubiquitous, the applications for which computers could be used became more diverse. Soon a need arose for smaller machines that could be used in more specialized departmental applications, and in the 1970s, thanks to companies like Xerox, Digital Equipment Corporation (DEC), and Figure 5-8 Mainframe computers in a "clean room" environment- No people work on this floor; the machines are controlled from another area. 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 Premises Technologies Figure 5-9 Mainframe disk pool, sometimes called a "Direct Access Storage Device (DASD) Farm" Figure 5-10 Tape library- Man