His Nibbler implements a 4-bit CPU using 7400 logic chips ... That’s a feat considering this is still just a design idea. It was made possible because he wrote a simulator based on the design.

serial-out and parallel-out shift register 4004: 4-bit CPU In April 1970, Noyce hired Federico Faggin from Fairchild in order to do the chip design. At that time the block diagram and basic ...