2.1 INTRODUCTION
In this chapter, we review techniques used to enhance the performance of a uniprocessor. A multiprocessor system or a parallel computer is composed of several uniprocessors and the performance of the entire system naturally depends, among other things, on the performance of the constituent uniprocessors. We also aim, in this chapter, to differentiate the techniques used to enhance uniprocessor performance from the techniques used to enhance multiprocessor performance, which are discussed in subsequent chapters.
Traditionally, building a computer was an expensive proposal. For almost 50 years, all effort went into designing faster single computer systems. It typically takes a microprocessor manufacturer 2 years to come up with the next central processing unit (CPU) version [1]. For the sake of the following discussion, we define a simple computer or processor as consisting of the following major components:
1. controller to coordinate the activities of the various processor components;
2. datapath or arithmetic and logic unit (ALU) that does all the required arithmetic and logic operations;
3. storage registers, on-chip cache, and memory; and
4. input/output (I/O) and networking to interface and communicate with the outside world.
The above components are sometimes referred to as the computer resources. Theses resources are shared between the different programs or processes running on the computer, and the job of the computer operating system (OS) is to organize the proper sharing and access to these resources. Making a processor run faster was accomplished through many techniques to enhance the datapath since it is the heart of any processor. We discuss datapath enhancements in the following subsections.