Build kit

Transistor Memory

A free kit. To use it fully you need the "Your Own CPU for a Pocket Game" kit, which in turn continues "A Watch and a Game from Gates". We build memory from latches — from one bit to 256 words — and put it into the processor instead of the ready-made primitive: the game runs on our own memory. Along the way: ferrite cores, a real bug caught with an oscilloscope, and a two-phase clock.

Start

This kit is free: all lessons are open, no sign-up needed.

What is inside

  1. Before you start
  2. A bit of history: how computers remembered
  3. Lesson 1. Cell and row: a 4-bit word
  4. Lesson 2. 16×4 memory: sixteen rows and picking one
  5. Lesson 3. 256×4 memory: the same circuit one level up
  6. Lesson 4. Your own memory in the processor — and the first error
  7. Lesson 5. Two-phase clock: the write never meets a new address
  8. Summary
  9. All the parts
  10. Instructions in pictures