Computer history | Microprocessors

When the processor moved onto a chip

Two early-1970s milestones show different sides of computing's shift toward smaller machines: the Intel 4004 put a processor on a microchip, while the Kenbak-1 offered an early personal-computer design built from integrated circuits.

Period: 1971 onwardSource: Computer History Museum

Two milestones in making computers smaller A large processor cabinet is shown becoming a compact microprocessor chip, alongside a separate early desktop computer with switches and indicator lights. Processor integration Early personal computing Processor assembled from components 4004: CPU on a chip Kenbak-1: switches, lights, 256 bytes Separate developments; not a direct product lineage
Concept illustration, not to scale: integrated processors and early personal computers were related developments, but the Kenbak-1 did not use an Intel 4004.

The Intel 4004: a computer's central logic on a chip

In 1971 Intel advertised the 4004, a microprocessor developed for Busicom, a Japanese calculator maker. The Computer History Museum describes it as the first microprocessor advertised and notes that it contained 2,250 transistors. Its design placed a processor's functions on a single chip—a major step in reducing the space and number of separate components needed for computation.

A microprocessor is a central processing unit implemented as an integrated circuit. Putting the processor on a chip did not instantly make every computer small or inexpensive, but it made it easier to build systems around compact, standardized processing components.

The Kenbak-1: computing for an individual

Also in 1971, John Blankenbaker's Kenbak-1 was advertised as an early personal computer. It used small- and medium-scale integrated circuits, had 256 bytes of memory, and used switches for input and lights for output. It was not based on a microprocessor: its computing logic was built from many separate integrated circuits.

These two machines represent different paths toward more accessible computing. The 4004 integrated processor circuitry; the Kenbak-1 packaged a computer intended for individual use. They should not be treated as stages in one product line, but both show how designers explored making computing smaller and more practical.

From early chips to everyday computers

Later microprocessors became more capable, while memory chips, storage, displays, and manufacturing also improved. Over decades, those developments helped make personal computers and embedded devices common. The modern laptop or phone is far more advanced, but its central processor still reflects the idea of concentrating computation into integrated silicon.

Key distinction: a microprocessor is a processor on a chip; an early personal computer is a complete system for individual use. A personal computer did not have to contain a microprocessor.

Sources and further reading

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