Packaging and Manufacturing
C. GORDON BELL, J. CRAIG MUDGE, and JOHN E. McNAMARA
As indicated in the previous chapter, computer engineering is more complicated than simply applying new technology to existing designs or designing new structures to exploit new technology. To design a successful new computer, the engineer must often deal with issues of packaging, manufacturing, software compatibility, marketing, and corporate policy. Some of these issues have been briefly referred to in the first two chapters, and some are beyond the scope of this text. However, two issues that can and should be discussed before exploring the case studies are packaging and manufacturing. Both of these are crucial to DEC, as well as to the computer industry in general.
Packaging is one of the most important elements of computer engineering, but also one of the most complex. The importance of packaging spans the size and performance range of computers from the super computers (CDC 6600, CDC 7600, Cray 1) to the pocket calculator. Seymour Cray, the designer of the super computers cited, has described packaging as the most difficult part of the computer designer's job. The two major problems he cites are heat removal and the thickness of the mat of wires covering the backplane. (The length of the wires is also important.) His rule of thumb indicates that with every generation of large computer (roughly five years), the size decreases by roughly a factor of 5, making these problems yet worse. In his latest machine, the Cray 1, the C-shaped physical structure is an effort to reduce the time-consuming length of backplane wires while providing paths for the freon cooling system by having wedge-shaped channels between the modules.
At the opposite end of the size and performance range, pocket calculators are also greatly influenced by packaging. In fact, they are deter mined by packaging. The first hand-held scientific calculator, the Hewlett-Packard HP35, was simply a new package for a common object, the calculator, which had been around for about a hundred years. It was not until semiconductor densities were high enough to permit implementation of a calculator in a few chips, and not until those chips could be repackaged in a particular fashion, that the hand-held calculator came into existence. Currently this embodiment is synonymous with the calculator name, but