Definition: Intel 4004

Intel's first microprocessor. Although Texas Instruments had already created a CPU on a chip for a customer, Intel's 4004 was the first to be sold to the general public. Until then, all chips were special purpose and electronic products often needed several chips to operate.

Designed by Marcian Hoff in 1971, the 4004 was a 4-bit, general-purpose CPU initially developed for the Japanese Busicom calculator. Prior to the 4004, custom-designed chips had to be made for each new calculator model. However, with the 4004 available, no new circuit designs on chips had to be made to add new features, only the software had to be updated. Intel acquired the rights to make the 4004 part of its product line.

A Small but Great Start
Given a minuscule 640 bytes of RAM to hold the data, the 4004 was very limited. Nevertheless, it was the start of a long line of CPU chips from Intel, which was a successful memory chip manufacturer when the 4004 was designed. The 4004's successor, the 4040, added interrupts and more ROM to hold more program instructions. See x86.

Make It General Purpose
Instead of designing a calculator chip, Hoff made a general-purpose processor that could be used for any processing task. In those days, computer CPUs were in cabinets the size of a refrigerator and cost hundreds of thousands of dollars. Thus began the new world of general-purpose CPUs on a chip, and since then, hundreds of billions have been produced (see microprocessor and microcontroller).

Intel 4004 CPU

With only 2,300 transistors, the general-purpose 4004 launched Intel into the microprocessor business. Running at 740 kHz (today's clocks are 2 GHz and up), the 4004 was part of a set that included the 4001 4KB ROM chip for instructions, the 4002 640-byte RAM chip and a 4003 chip for input and output. See clock. (Image courtesy of Intel Corporation.)

The 4004-Based Busicom Calculator

A Half Century of Progress

Intel microprocessors today have a million times more transistors than the 4004. For example, this i9 CPU contains nearly three billion transistors compared to 2,300. (Image courtesy of Intel Corporation.)


              FIFTY YEAR COMPARISON
               OF INTEL CPU CHIPS

                4004         Core
               (1971)       (2021)

 Number of
  transistors   2,300   approx 3 billion

 Register size
  (bits)          4          64

 Clock speed     750 kHz    5.2 GHz

 Cores            1          16

 Threads          1          24

 Wafer size
  (inches)        2         11.8

 Node size (nm)  10,000      10

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Definition: Intel 4004