ABSTRACT
The central processing unit (CPU) is the brain of any computer system based on the von Neumann (Princeton) or Harvar d architectures introduced in Chapter 1. Parallel machines have many such brains, but normally each of them is based on the same principles used to design the CPU in a
uniprocessor
(single CPU) system. A typical CPU has thr ee major parts: the arithmetic/ logic unit (ALU), which performs calculations; internal registers, which provide temporary storage for data to be used in calculations; and the contr ol unit, which directs and sequences all operations of the ALU and registers, as well as the rest of the machine. (A block diagram of a typical simple CPU is shown in Figure 3.1.) The control unit that is responsible for carrying out the sequential execution of the stor ed program in memory is the hallmark of the von Neumann-type machine, using the r egisters and the arithmetic and logical cir cuits (together known as the
datapath
) to do the work. The
design of the control unit and datapath have a major impact on the perfor - mance of the processor and its suitability for various types of applications. CPU design is a critical component of overall system design. In this chapter, we will look at important basic aspects of the design of a typical general-purpose processor; in the following chapter , we will go beyond the basics and look at modern techniques for impr oving CPU performance.
