The CMU RT-CAD system
Daniel P. Siewiorek, Mario R. Barbacci · 1976
As technology has evolved the primitive components available to a digital system designer have changed dramatically. Twenty-five years ago the designer constructed systems out of circuit level components such as resistors and diodes. Subsequently switching circuit level components, as represented by gates and flip-flops, became available as small scale integration (SSI) components. With the introduction of medium scale integration (MSI) register transfer level components appeared: arithmetic and logic units, registers, shift registers, etc. The advent of large scale integration (LSI) has made memories and even processors primitive components from which systems are designed. Two trends can be observed from this technological evolution: (1) primitive components continue to increase in complexity and (2) the rate of introduction of new components continues to increase.