Technology Progress in Logic and Memories
C. GORDON BELL, J. CRAIG MUDGE, and JOHN E. McNAMARA
It is customary when reviewing the history of an industry to ascribe events to either market pull or technology push. The history of the auto industry contains many good examples of market pull, such as the trends toward large cars, small cars, tail fins, and hood ornaments. The history of the computer industry, on the other hand, is almost solely one of technology push.
Technology push in the computer industry has been strongest in the areas of logic and memory, as the case studies in the following chapters indicate. Where the following chapters give examples of the effects of the technology push in these areas, this chapter explores individual elements of that push, with particular emphasis on the role of semiconductors.
Semiconductor devices are discussed from the viewpoint of the user because, until recently, DEC has always bought its semiconductors (especially integrated circuits) from semiconductor manufacturers, and its engineers (users of integrated circuits) have viewed the integrated circuit as a black box with a carefully defined set of electrical and functional parameters. Most design engineers will probably continue to hold that view (and be encouraged to do so), even though some integrated circuits will be supplied by an in-house design and manufacturing facility. The advantages and disadvantages of in- house integrated circuit design will be discussed later in the chapter.
The portion of the discussion dealing with semiconductors begins by presenting a family tree of the possible technologies, arranged ac cording to the function each carries out and showing how these have evolved over the last two or three generations to affect computer engineering. The cost, density, performance, and reliability parameters are briefly reviewed; the application of semiconductors, using various logic design methods, is then discussed with particular emphasis on how the semiconductor technology has pushed the design methods.
The discussion of the use of semiconductors in logic applications is followed by a section on memories for primary, secondary, and tertiary storage. While semiconductors have been a dominant factor in technology push within the computer industry, for both logic and memory applications, magnetic recording density on disks and tapes has evolved rapidly, too, and must be understood as a component of cost and as a limit of system performance.