Ben Eater's Homebuilt Computer

[Bob Kuczewski]

Build an 8-bit computer from scratch

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A fellow named Ben Eater did a remarkable job of building (and documenting) an 8-bit computer from scratch using simple logic gates and integrated circuits. You can find his full documentation here:

      https://eater.net/8bit

Here's an interview with Ben related to his work at the Khan Academy :

https://www.youtube.com/watch?v=MAtQe5zpNsw


Here are links to the videos from Ben's site about his home built computer:

Introduction and Background Material

Post    YouTube - Overview and Plans
Post    YouTube - Programming and Architecture
Post    YouTube - Single Stepping through a Program
Post    YouTube - Programming C to Assembly to Machine
Post    YouTube - Fibonacci Program Example
Post    YouTube - How Semiconductors Work
Post    YouTube - How Transistors Work
Post    YouTube - Transistors as Logic Gates
Post    YouTube - Logic Gates and Flip Flops for Memory
Post    YouTube - Turning an SR Latch into a D Latch
Post    YouTube - Edge Triggering to get a D Flip-Flop

Clock

Post    YouTube - Clock 555 Timer in Astable Mode
Post    YouTube - Clock 555 Timer in Monostable Mode
Post    YouTube - Clocking, Single-Stepping, Debouncing
Post    YouTube - Completed Clock Module

Registers

Post    YouTube - Registers using Tri-State Buffers
Post    YouTube - Description of 74LS245 Tri-State Buffer
Post    YouTube - Simple 1-Bit Register
Post    YouTube - Use of 74LS173 Registers to Store/Display
Post    YouTube - Registers A, B, and Inst. Interface via Bus

ALU

Post    YouTube - Using Logic Gates to Add 4-bit Numbers
Post    YouTube - Negative Numbers and 2's Complement
Post    YouTube - Description of Arithmetic Logic Unit (ALU)
Post    YouTube - Building the Arithmetic Logic Unit (ALU)
Post    YouTube - Diagnosing Problems in the ALU
Post    YouTube - Operation of the ALU to add and subtract

RAM

Post    YouTube - Random Access Memory (RAM) Design
Post    YouTube - Construction of the RAM Module
Post    YouTube - Addressing RAM Manually and with Control Logic
Post    YouTube - Completed RAM Module with Address, Data, Control
Post    YouTube - Testing the RAM Module

Program Counter

Post    YouTube - Description of a J-K Flip-Flop
Post    YouTube - Exploring race conditions in the J-K Flip-Flop
Post    YouTube - Master-Slave J-K Flip-Flop to eliminate racing
Post    YouTube - Exploring the 74LS76 J-K Flip-Flop for Counting
Post    YouTube - Program Counter Design with the 74LS161
Post    YouTube - Building the Program Counter

Output register

Post    YouTube - Using Logic Gates to Build 7-Segment Displays
Post    YouTube - Using an EEPROM to Build 7-Segment Displays
Post    YouTube - Building an EEPROM Programmer using an Arduino
Post    YouTube - Building the Computer Display Module

Bringing it all together

Post    YouTube - Building and Connecting Modules via the Bus
Post    YouTube - Connecting Control Signals to all Modules

CPU control logic

Post    YouTube - Initial Design of the Control Logic
Post    YouTube - Microcoding the Control Logic
Post    YouTube - Using an EEPROM for Microcoding (LDA,ADD,OUT,HLT)
Post    YouTube - Reset Button, Power Supply, and Hardware Review
Post    YouTube - Expanding the Instruction Set for Subtraction
Post    YouTube - Expanding the Instruction Set with STA, LDI, JMP
Post    YouTube - Computing Everything? Turing Complete and Branching
Post    YouTube - Adding Hardware to support Jumps on Zero and Carry
Post    YouTube - Updating the Microcode for JZ and JC instructions used in multiply program

These videos are available through these links and on the following pages.

[Bob Kuczewski]

Introduction and Overview

In Ben's first video he gives an overview of the computer that he built, and he gives his plans for a series of videos to describe it.

https://www.youtube.com/watch?v=HyznrdDSSGM

[Bob Kuczewski]

In this video, Ben describes the programming of his computer along with an overview of the architecture.

https://www.youtube.com/watch?v=9PPrrSyubG0

[Bob Kuczewski]

In this video, Ben demonstrates single stepping through a short program.

https://www.youtube.com/watch?v=35zLnS3fXeA

[Bob Kuczewski]

In this video, Ben shows how a program written in a high level language gets converted into the low level computer instructions to do a task. In this example, the program will compute the Fibonacci sequence up to 255.

https://www.youtube.com/watch?v=yOyaJXpAYZQ

[Bob Kuczewski]

In this example, Ben shows how the same Fibonacci program could be translated into the machine code instructions for his own computer.

https://www.youtube.com/watch?v=a73ZXDJtU48

[Bob Kuczewski]

In this video, Ben takes a diversion to explain how semiconductors work.

https://www.youtube.com/watch?v=33vbFFFn04k

[Bob Kuczewski]

In this video, Ben continues the previous backround discussion to explain how transistors work.

https://www.youtube.com/watch?v=DXvAlwMAxiA

[Bob Kuczewski]

In this video, Ben explains how transistors (described earlier) can be used to perform simple logic functions known as logic gates.

https://www.youtube.com/watch?v=sTu3LwpF6XI

[Bob Kuczewski]

In this video, Ben explains how to use the simple logic gates (from the previous video) to build a simple memory storage device - the Set Reset Latch (SR Latch). Ben builds the SR Latch from two cross-coupled NOR gates, and he explains the operation in careful detail.

https://www.youtube.com/watch?v=KM0DdEaY5sY