In 1971, Intel stepped out of its traditional role in making memory chips to release the world’s very first microprocessor, called the Intel 4004. Advertised as a “computer on a chip,” the Intel 4004 was a 4-bit processor capable of vastly improving a number of applications, including calculators. In fact, the first calculator with the Intel 4004 inside can be seen in the Computer History Museum.

Intel 4004

Source: http://velox.stanford.edu/group/chips_micropro_body.html

Fedorico Faggin, the chip’s designer, strongly believed that the Intel 4004 should be made available to the general market for broader computing needs, and so in November 1971, Intel released a package it called the MCS-4 (Micro Computing System – 4 bit). This consisted of:

• a 2048-bit ROM with a 4-bit programmable input-output port (4001)
• a 4-registers x 20-locations x 4-bit RAM data memory with a 4-bit output port (4002)
• an input-output expansion chip, consisting of a static shift register with serial input and serial and parallel output (4003)
• a 4-bit CPU chip (4004)

The HP-48 Saturn series of calculators, launched in 1993, also essentially represented 4-bit computing, since data retrieval and addressing was done in 4-bit chunks. These calculators did, however, have an 8-bit CPU and data bus.

In 1973, Intel released the first widely-used 8-bit processor, called the Intel 8008. In this system, the data bus and addresses were 8-bit units. Shortly after this release, the Zilog Z80 and the Motorola 6800 hit the market. 8-bit processors were found, during the 1970s and 1980s in many home computers and video game consoles. Today, 8-bit and 16-bit chips form the core of many embedded systems (computers designed for a specific rather than general use).

The 32-bit processor (Intel’s 80386), introduced in the late 1970s, has remained the mainstream personal computer chip for over two decades. When it was released, the UNIX operating system, which had originally been designed for 16-bit architecture, was quickly modified to support 32 bits. Currently, most of the world’s computing is done on 32-bit systems, which allow fast computations on numbers greater than 2 billion. As disc storage, memory chip manufacturing, and CPU power continually improve, however, the demand for even larger addressing structures has become evident.