The Growth of Interest in Microprogramming: A Literature Survey
ACM Computing Surveys (CSUR)
A view of computer architecture
Communications of the ACM
A bit slice architecture for microprogrammable machines
MICRO 9 Proceedings of the 9th annual workshop on Microprogramming
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The fundamental aspect of microprogramming as introduced by Wilkes in 1951 [1,2] is the implementation of sequential control with stored or programmed logic in contrast to hardwired random logic involving adhoc connections of large numbers of simple logic gates. The microprogramming became practical with the availability of high speed memories at reasonable cost during the 60s and has become a very popular tool even for the design of small, low-cost computers. [3,4] ,Now steadily improving performance of LSI memories at declining cost and availability of LSI functional components to implement combinatorial and sequential logic functions tend to obliterate the classic distinction between logic and memory based on old technologies, i.e., electronic logic and magnetic memory with incompatible speeds, signal levels, and power requirements. Although we still do have minor incompatibilities between TTL and MOS signal levels, these are bang eliminated with introduction of NMOS (N-channel Metal Oxide Semiconductor) LSI devices which are fully TTL compatible. The full compatibility of memory and logic at hardware level, and availability of LSI memories and processing elements in convenient sizes, speeds and capacities at a steadily declining cost seem to favor use of programmed logic over hardwired random logic in many old and new applications, just as the microprogramming has been favored over hardwired logic for the design of control unit. This technological development provides the computer architect and digital system designer with new freedom to distribute “intelligent, programmable” chips throughout his system from the control processor within a central processor to “dumb” peripheral devices. This unprecedented design freedom seems to be the most significant aspect of LSI technology that the designer must realize before he can bring its benefits to users. This paper attempts to explore potentials and limits of LSI technology, and its profound implications for microprogramming, computer design, and computer usage.