PC Hardware in a Nutshell, Second Edition

Chapter 4. Processors

The processor, also called the microprocessor or CPU (for Central Processing Unit), is the brain of the PC. It performs all general computing tasks and coordinates tasks done by memory, video, disk storage, and other system components. The CPU is a very complex chip that resides directly on the motherboard of most PCs, but may sometimes reside on a daughtercard that connects to the motherboard via a dedicated specialized slot.

Processor Design

A processor executes programs—including the operating system itself and the user applications—all of which perform useful work. From the processor’s point of view, a program is simply a group of low-level instructions that it executes more or less in sequence as it receives them. How efficiently and effectively the processor executes instructions is determined by its internal design, also called its architecture. The CPU architecture, in conjunction with CPU speed, determines how fast the CPU executes instructions of various types. The external design of the processor, specifically its external interfaces, determines how fast it communicates information back and forth with external cache, main memory, the chipset, and other system components.

Processor Components

Modern processors have the following internal components:

Execution unit

The core of the CPU, the execution unit processes instructions.

Branch predictor

The branch predictor attempts to guess where the program will jump (branch) next, allowing the Prefetch ...