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Intel 4004

The Intel 4004 was the first CPU designed and manufactured by Intel, introduced in November, 1971.

The chip (limited by its 16 pin DIP packaging) had a single 4-bit bus.

Originally designed for Busicom for use in their calculators, Intel provided a family of custom chips to support it. These chips included all needed circuits. For example the 12-bit Program address, which could access 4K bytes of memory, was latched by the Program ROM chips as the 4004 transmitted it 4-bits at a time.

Features

  • Separate Program and Data memories (Harvard architecture)
  • Instruction set contains 46 instructions
  • Register set contains 16 4-bit registers
  • Internal Subroutine stack is 3 levels deep

Available support chips

  • 4001 - 256 bytes ROM w/ 4-bit I/O port
  • 4002 - 80 4-bit words RAM w/ 4-bit Output port
  • 4003 - 10-bit Shift Register
  • 4008 - Address Latch for access to standard memory chips
  • 4009 - Program & I/O access to standard memory and I/O chips

For calculator and controller use this was a very effective design. There are even a few older traffic light control systems in use built with these chips!



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