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Computer History: From The Antikythera Mechanism To The Modern Era

The Information Technology Revolution - The First Processors (CPUs)

In this section we will review some of the most significant developments in Information Technology (IT) from the early 1970s, including the first computer processors.

In 1969 a Japanese company, called Busicom, made an order to Intel for the design of 12 special purpose integrated circuits (ICs), which would be used in a new line of programmable electronic calculators. Intel assigned the study of Busicom's design to Marcian Edward "Ted" Hoff. After looking into this matter, Hoff decided to bypass Busicom's initial design and proposed a new architecture that included a single IC that would adopt the characteristics of a general purpose processor.

Hoff's new architecture was utilized by Federico Faggin, who was the leader of the implementation team, and the result was the first microprocessor or Central Processing Unit (CPU), called 4004. This CPU had a 4 bit architecture, meaning that it could process data with 4 bit length, and included 256 bytes of Read Only Memory (ROM), 32 bit RAM and a 10 bit shift register. The 4004 used 2,300 transistors and could perform 60,000 operations per second. The maximum operating frequency of this CPU was 740 KHz.

Obviously the strongest asset of the 4004 CPU was that it could be used for a variety of tasks, by simply feeding it with another program. Nowadays this seems like a really simple concept, but at that time it was considered to be a great innovation to have a general purpose CPU that could be programmed to deal with different tasks.

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Shortly after the release of the 4004, in 1972, Intel introduced the 8008 CPU, which essentially was the 8-bit version of its predecessor. The 8008 was the first CPU that was supported by a high level compiler, the PL/M. Two years later, in 1974, the Intel 8080 was introduced, retaining the 8-bit architecture. With its 4,500 transistors it could perform 200,000 operations per second.

In 1974 Motorola introduced the 6800 CPU. In 1975 the 6502 was released by MOS Technology, and in 1976 the legendary Zilog Z80 made its debut.


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