I've been studying this chip lately. I can easily find block-level architecture or transistor-level diagrams on the web, but nothing in between.

For example, I'm curious about how the 2-word instructions are implemented, or how the ALU is implemented specifically.

Does anyone know is this knid of information is available anywhere?

  • 9
    You may want to mention the resources you're already familiar with, so that people will not have to waste their time responding with information which would not be helpful to you.
    – Leo B.
    Jul 2, 2021 at 22:53
  • 1
    A description of the 4004 using Verilog can be found at opencores.org/projects/mcs-4
    – JRN
    Jul 3, 2021 at 2:09
  • 3
    This transistor-level schematic is pretty well annotated. Jul 3, 2021 at 2:18
  • I am not sure I understand what you want. Conceptual? Logical? Physical? Signals/timing? Flowchart? How those interact with each other?
    – C. M.
    Jul 3, 2021 at 17:53
  • I'm looking for something more at the logical level. Jul 5, 2021 at 13:40

2 Answers 2


The following references contain more detailed information than can be found in the Intel 4004 datasheets.


Two IEEE papers written by Federico Faggin, the chief designer of the 4004:

  • The History of the 4004, written by Faggin and three other members of the 4004 design team, for IEEE Micro, Dec. 1996. Includes timing diagrams and block diagrams of the 4004 CPU.

  • The Making of the First Microprocessor, solely by Faggin, for IEEE Solid-State Circuits Magazine, Winter 2009. More oriented at the transistor and gate levels of the design. Also describes the 4001, 4002, and 4003 chips.

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