Cost, performance and size tradeoffs for different levels in a memory hierarchy

Abstract

This paper evaluates the effect of cost and performance tradeoffs on memory system hierarchies achieved by varying the total amount of memory at any two adjacent levels. The hierarchy is analyzed in a multiprogramming mode by using a two server cyclic queuing model. As an example, a two level hierarchy of Bipolar, MOS and a three level hierarchy of Bipolar, MOS, and CCD for the primary memory are compared. A figure of merit that is a function of the number of instructions executed by a given processor is used to evaluate the different memory hierarchies. It is shown that up to 3:1 advantage in performance can be achieved by using a three level rather than the two level hierarchy at the same total cost. The effect on the performance of the memory hierarchy due to the change in the degree of multiprogramming, the speed and cost of CCD technology used, the speed of the CPU used and the amount of CCD and MOS memory used are then evaluated. The performance of two and three level hierarchies is also analyzed as a function of the primary memory requirements versus the CCD speed.