How Do Computers Really Work?

“Wisdom is not a product of schooling but of the lifelong attempt to acquire it.”

For how many of our waking hours we spend each day staring into a screen, it’s remarkable how few people understand whats happening on the other side of the glass. It may sound like an overtly complex engineering feat, but it turns out computers, if explained clearly, aren’t all that confusing.

In this series, we will start by designing a basic CPU from scratch called the SAP-1 which was designed by Albert Paul Malvino in 1976. This simple yet powerful processor is designed to be easy to understand while also providing some impressive capabilities. You can even build this CPU after reading this series, which I did in 2020 when first introduced to the model.

Whether you are a computer science major or a curious learner without engineering experience, this guide is intended to be read by any audience and makes no prior assumption of any knowledge beyond basic math concepts you (hopefully) learned in middle school.

Chapter 01 - In Progress…
Chapter 02 - How Humans See Numbers
Chapter 03 - How Computers See Numbers
Chapter 04 - Fixed-Width Numbers
Chapter 05 - What about Negative Numbers?
Chapter 06 - Logic Gates
Chapter 07 - Addition with Logic Gates
Chapter 08 - Ripple Carry Adders
Chapter 09 - Arithmetic Logic Unit (ALU)
Chapter 10 - Storing Data with Logic Gates
Chapter 11 - Building a Register
Chapter 12 - An Interlude: How Calculators Work

Future Chapters

Chapter XX - The Clock (Propogation Delay)
Chapter XX - Interlude: Building a Counter
Chapter XX - RAM
Chapter XX - The Memory Address Register (MAR)
Chapter XX - Program Counter and Computer Architecture
Chapter XX - The BUS
Chapter XX - Introduction to Control Unit
Chapter XX - Instruction Register
Chapter XX - Revisiting Control and Designing our Instruction Set
Chapter XX - Output Register and Display
Chapter XX - Make this an 16-Bit CPU
Chapter XX - Next Steps
Chapter XX - Latency and Throughput: Pipelining
Chapter XX - The Three Main Principles of an Operating System
Chapter XX - Modifying Hardware to Support an OS
Chapter XX - Compilers
Chapter XX - Programming Languages
Chapter XX - Designing a LISP-Like Programming Language
Chapter XX - Building a Compiler for our Programming Language
Chapter XX - Multi Core CPUs
Chapter XX - Synchornizing Threads

Logic Gate Diagram

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Let's Understand How a CPU Works

How Do Computers Really Work?

Table of Contents

Future Chapters