Intel Advertises the 4004 Microprocessor

In Brief

Intel publicly introduced the 4004 microprocessor through an advertisement dated November 15, 1971. The chip was part of a system initially developed for a calculator project. Putting a central processing unit on a small integrated circuit helped open new possibilities for programmable devices. The 4004 worked with supporting chips rather than functioning as a complete computer on its own. Its importance should not be simplified into the claim that one chip instantly created personal computing.

What the Advertisement Offered

On November 15, 1971, an Intel advertisement in Electronic News announced the 4004 as part of its MCS-4 family. This is a date for public marketing, not the day work began or the day every early chip was shipped. The 4004 put the main functions of a programmable central processor on one integrated circuit. It worked with companion chips for memory and other tasks. A complete computer still required those components and a way to communicate with the outside world. The innovation was an important reduction in how much dedicated hardware was needed for the part that interpreted and executed instructions.

A Calculator Created the Opportunity

The design grew from work for Busicom, a Japanese calculator maker. A system using a programmable processor could support different functions through changes to instructions instead of requiring a new circuit for every variation. Ted Hoff, Stanley Mazor, Federico Faggin and Masatoshi Shima made distinct contributions to architecture, implementation and the customer's design. Manufacturing a working chip called for more than proposing the architecture. Timing, transistor behavior and layout had to fit the process Intel could actually use. The calculator project supplied a concrete problem against which those choices could be tested.

What Four Bits Meant

The processor handled information in small units well suited to the original problem. It could execute instructions, manipulate values and use memory with the other chips. It was far less capable than processors that came later, but the scale of the comparison is misleading if modern expectations are imposed on a calculator. A designer could make a useful system around a general processor and program it for the needed work. That principle mattered more than whether the early chip could perform tasks no customer was then proposing.

Why the Public Offer Mattered

Intel obtained rights to market the technology beyond the original calculator arrangement. The advertisement invited other designers to consider using it in products Intel had not commissioned or planned. Claims about a universal first depend on how a microprocessor is defined and how early special-purpose or unpublished designs are counted. The 4004's well documented significance is commercial: it made a single-chip programmable CPU available in a product family. What became ordinary later was not merely a smaller calculator, but the idea that the same processing hardware could be made useful in different devices by changing its software.