Definition: Intel 4004

The first microprocessor. Although Texas Instruments had already created a CPU on a chip for a customer, Intel's 4004 was the first to sell to the general public. Designed by Marcian Hoff in 1971, the 4004 was a 4-bit, general-purpose CPU initially developed for the Japanese Busicom calculator. Intel acquired the rights to make the chip part of its product line.

Running at a clock rate of 740 kHz, the 4004 had 4KB of read-only memory (ROM) for the instructions and 640 bytes of random access memory (RAM) for processing the input.

A Small But Great Start
Given the minuscule amount of RAM, the 4004 was limited. Nevertheless, it was the start of a long line of microprocessors from Intel, which until then was a successful memory chip manufacturer. The 4004's successor, the 4040, added interrupts and more program ROM. 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 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).

The 4004 CPU

With only 2,300 transistors, the general-purpose 4004 launched Intel into the microprocessor business. (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