The Architecture of Computer Hardware, Systems Software, & Networking: An Information Technology Approach, 5th Edition

CHAPTER 7

THE CPU AND MEMORY

SHOE - NEW BUSINESS © (1993) MACNELLY. DISTRIBUTED BY KING FEATURES SYNDICATE

7.0 INTRODUCTION

The previous chapter provided a detailed introduction to the Little Man model of a computer. In that chapter, we introduced a format, using a three-digit number divided into op code and address fields, for the instructions that a computer can perform. We introduced an instruction set that we indicated was representative of those found in a real computer. We also showed the steps that are performed by the Little Man in order to execute one of these instructions.

In this chapter and the next, we will extend these concepts to the real computer. Our primary emphasis in this chapter is on the central processing unit (CPU), together with memory. In the real computer, memory is actually separated both physically and functionally from the CPU. Memory and the CPU are intimately related in the operation of the computer, however, and so we will treat memory together with the CPU for the convenience of our discussion. Since every instruction requires memory access,¹ it makes sense to discuss the two together.

We will use the Little Man model and its instruction set as a guideline for our discussion. The Little Man instruction set is fundamentally similar to the instruction sets of many different computers. Of course, the Little Man instruction set is based on a decimal ...