Chapter 1 CHAPTER 1 An Introduction to Computer Architecture Each machine has its own, unique personality which probably could be defined as the intuitive sum total of everything you know and feel about it. This personality constantly changes, usually for the worse, but sometimes surprisingly for the better... —Robert M. Pirsig Zen and the Art of Motorcycle Maintenance This book is about designing and building specialized computers. We all know what a computer is. It’s that box that sits on your desk, quietly purring away (or rattling if the fan is shot), running your programs and regularly crashing (if you’re not running some variety of Unix). Inside that box is the electronics that runs your software, stores your information, and connects you to the world. It’s all about processing information. Designing a computer, therefore, is about designing a machine that holds and manipulates data. Computer systems fall into essentially two