All labs

Build a CPU

Start with switches and lamps. Build the parts that add, choose and remember, wire them into a processor, then write a program and watch it move through the machine you built.

Briefing

You start with nothing but switches and lamps. Each board you finish becomes a part you build the next one from: a gate, then an adder, then memory, until you have a processor — and the last board runs a program through the machine you built.

You'll learn to

  • Build XOR, an adder and a multiplexer from AND, OR and NOT
  • Explain how a circuit can add, choose and remember
  • Wire those parts into a working ALU and a tiny CPU
  • Trace a program as it moves through the datapath
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Start: Logic gates
Before you build a CPUOptional warm-upTruth tables, binary, and why adding two bits needs two digits. About ten minutes.

  1. Logic gates

    Up next

    The only parts a computer actually has

  2. Exclusive OR

    Making a gate that does not exist

  3. Half adder

    Where arithmetic starts

  4. Full adder

    Adding a carry back in

  5. Multiplexer

    How a machine chooses

  6. The ALU

    Operations, plus a way to pick one

  7. Registers and memory

    Somewhere to put things

  8. Run a program

    Instruction, decode, control signals, result

  9. Real architectures

    What a genuine processor adds