The Legacy Of The Intel 4004

First hand accounts and two controversies

Oct 11, 2022

Intel 4004 with supporting integrated circuits

We’ve already discussed Robert Noyce’s influence on the Intel 4004, the limitations and quirks of the architecture and how it was used to implement a virtual machine in the Busicom calculator.

So much has been written about the 4004 that, rather than write any more, it felt more useful to highlight some ‘further reading’ with the most insightful analyses over the last fifty years, particularly from those who were directly involved.

The History Of The 4004

Let’s start with the story of the 4004 as told by those who made it happen. The 1996 IEEE article by Federico Faggin, Ted Hoff, Stan Mazor and Masatoshi Shima, tells the story in a clear and comprehensive way. Sadly this is behind a paywall (link) but there may be other sources.

50th Anniversary

For a more recent discussion with three of the key members of the 4004 team, the Computer History Museum, held a webinar to celebrate the 50th anniversary.

Federico Faggin - Silicon

For an individual perspective from Federico Faggin, I’d recommend his recent autiobiography, entitled simply ‘Silicon’. It covers a lot more than just his time at Intel and it’s a great read. Amazon (non-affiliate) link here.

As you can see the 4004 features on the front cover.

What Constituted Innovation?

The first controversy surrounding the 4004 is what was the part of design that was really innovative? William Aspray’s paper ‘The Intel 4004 Microprocessor: What Constituted Invention?’ (again sadly paywalled - link) discusses this in detail.

Aspray’s paper does a great job of assessing both what constituted invention and the contributions of the individuals involved in the project. Perhaps the most important conclusion is that:

that the conceptualization of the microprocessor, which was Hoff’s principal contribution to the 4004 project, was independently conceived in other companies and Hoff was aware of some of this work.

In other words, the idea of a single chip microprocessor wasn’t really original. I’d go so far as to say that the 4004 wasn’t an invention, rather, as others have described it, it represents a ‘technical milestone’.

The First Microprocessor?

This takes us on to the second controversy about the 4004. Was it really the first microprocessor?

For some answers to this question we turn to Ken Shirriff in his article, ‘The Texas Instruments TMX 1795: the (almost) first, forgotten microprocessor’ (link).

This article highlights some of the possible rivals for the title. The Texas Instruments TMX 1795, the Four Phase AL1, The Viatron, the MP 944 (built for the F14 Tomcat fighter plane), the Intel 8008 and finally another TI chip the TMS 0100.

So what’s the answer to who was first? To quote Ken Shirriff: