# Microprocessor Design/Introduction
## About This Book

Computers and computer systems are a pervasive part of the modern world. Aside from just the common desktop PC, there are a number of other types of specialized computer systems that pop up in many different places. The central component of these computers and computer systems is the microprocessor, or the CPU. The CPU (short for "Central Processing Unit") is essentially the brains behind the computer system, it is the component that "computes". This book is going to discuss what microprocessor units do, how they do it, and how they are designed.
This book is going to discuss the design of microprocessor units, but it will not discuss the design of complete computer systems nor the design of other computer components or peripherals. Some microprocessor designs will be implemented and synthesized in Hardware Description Languages, such as Verilog or VHDL. The book will be organized to discuss simple designs and concepts first, and expand the initial designs to include more complicated concepts as the book progresses.
This book will attempt to discuss the basic concepts and theory of microprocessor design from an abstract level, and give real-world examples as necessary. This book will not focus on studying any particular processor architecture, although several of the most common architectures will appear frequently in examples and notes.

## How Will This Book Be Organized?

The first section of the book will review computer architecture, and will give a brief overview of the components of a computer, the components of a microprocessor, and some of the basic architectures of modern microprocessors.
The second section will discuss in some detail the individual components of a microcontroller, what they do, and how they are designed.
The third section will focus in on the ALU and FPU, and will discuss implementation of particular mathematical operations.
The fourth section will discuss the various design paradigms, starting with the most simple single cycle machine to more complicated exotic architectures such as vector and VLIW machines.
Additional chapters will serve as extensions and support chapters for concepts discussed in the first four sections.

## Prerequisites

This book will rely on some important background information that is currently covered in a number of other local wikibooks. Readers of this book will find the following prerequisites important to understand the material in this book:
* Digital Circuits
* Programmable Logic
* Embedded Systems
* Assembly Language
All readers must be familiar with binary numbers and also hexadecimal numbers. These notations will be used throughout the book without any prior explanation. Readers of this book should be familiar with at least one assembly language, and should also be familiar with a hardware description language. This book will use both types of languages in the main narrative of the text without offering explanation beforehand. Appendices might be included that contain primers on this material.
Readers of this book will also find some pieces of software helpful in examples. Specifically, assemblers and assembly language simulators will help with many of the examples. Likewise, HDL compilers and simulators will be useful in the design examples. If free versions of these software programs can be found, links will be added in an appendix.

## Who Is This Book For?

This book is designed to accompany an advanced undergraduate or graduate study in the field of microprocessor design. Students in the areas of Electrical Engineering, Computer Engineering, or Computer Science will likely find this book to be the most useful. The basic subjects in this field will be covered, and more advanced topics will be included depending on the proficiencies of the authors. Many of the topics considered in this book will apply to the design of many different types of digital hardware, including ASICs. However, the main narrative of the book, and the ultimate goals of the book will be focused on microcontrollers and microprocessors, not other ASICs.

## What This Book Will Not Cover

This book is about the design of micro-controllers and microprocessors only. This book will not cover the following topics in any detail, although some mention might be made of them as a matter of interest:
* Transistor mechanics, semiconductors, or integrated circuit fabrication (Microtechnology)
* Digital Circuit Logic, Design or Layout (Programmable Logic)
* Design or interfacing with other computer components or peripherals (Embedded Systems)
* Design or implementation of communication protocols used to communicate between computer components (Serial Programming)
* Design or creation of computer software (Computer Programming)
* Design of System-on-a-Chip hardware or any device with an integrated micro-controller
* How to select an off-the-shelf CPU (How To Assemble A Desktop PC/Choosing the parts/CPU)

## Terminology

Throughout the book, the words "Microprocessor", "Microcontroller", "Processor", and "CPU" will all generally be used interchangeably to denote a digital processing element capable of performing arithmetic and quantitative comparisons. We may differentiate between these terms in individual sections, but an explanation of the differences will always be provided.