Cambridge-1: a 4-bit 7400 series based CPU

The Cambridge-1 features a 4-bit word size, 7400 series ICs galore and blinkenlights-a-plenty.

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A month long project and originally conceived to showcase at the Retro Computer Festival 19, the Cambridge-1 CPU features a 4-bit word size, blinkenlights-a-plenty, and some (slightly naughty) Arduino based cheating to virtualise the control unit. It also contains an 8-bit data and address path with some instruction set tricks to perform 8-bit operations as well. All this at a whopping clock speed of 40Hz too.

Cambridge-1 CPU spec:

  • 4-bit word size
  • 4-bit adder (74HC283)
  • 8-bit data path
  • 8-bit address path
  • 8-bit memory word (4-bit instruction + 4-bit operand)
  • 40 Hz clock speed
  • 16 instruction ISA
  • Virtualised control unit (using an Arduino Micro)
  • Program loading (into RAM) via Arduino Micro
  • Blinkenlights!!!!!!!!

For more information about the build please visit:

Specific build information, including the instruction set can be found at:

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ARITH-MATIC wrote 09/26/2019 at 23:47 point

haha, thanks @Dan Maloney ;)

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Dan Maloney wrote 09/26/2019 at 15:26 point

This is very cool! Your reveal in the video is like the opening scene in Star Wars: Episode 4 where the Star Destroyer just keeps going - same thing with your breadboard, just keeps going. Love the wiring harness too.

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