Parallel Functional Units

Abstract

In Chapter 4 we saw an example of the use of parallel functional units in the IBM System/360 Model 91. In this machine the parallelism was introduced as a means of enhancing the performance of a processor at the top end of a range of general purpose computers. In the case of the CDC 6600, performance was the principal criterion of the design, and as we saw in Chapter 2, the use of parallel functional units with an instruction set capable of exploiting this parallelism was a key feature. In this chapter we shall consider the design of the CDC 6600 central processor, with particular emphasis on the Scoreboard, the mechanism used to control the operation of these functional units. We shall then go on to consider some of the design modifications introduced in the CDC 7600, the successor to the 6600, and then see how limitations inherent in the 6600/7600 architecture led to the CRAY-1 design. We shall consider the design of this machine in some detail.