The unexpanded ZX81 is equipped with 1K of RAM – this is either provided by 2 x 2114 chips, or a single 4118 chip. There are positions on the motherboard for both configurations.

2114 RAM Chip

  • A0-A9: Address Lines
  • IO1-IO4: Data Lines
  • S: Chip Select
  • W: Write Enable


The 2114 chips are 4096 bit static RAM organised as 1K x 4bits, which is why two are required to make up 1K x 8bits