Transistors, ICs & Microprocessors

2nd, 3rd and 4th Generation Computers


Transistors were invented in 1947. The early ones were very delicate, electrically. I remember that we had just one when I was in College. They were used in second generation computers. Early transistors were built on a substrate of germanium. Before long, silicon, a related element in the carbon family, was used instead; making more rugged transistors.

Integrated circuits

In about 1960, it was possible to put more than one transistor on a slice of silicon as small as 1 mm square. A circuit with just four logic gates, each with about 16 transistors was mounted on a one inch piece of plastic less than a third of inch wide.

Small scale integrated circuit
Small scale integrated circuit

Computers using ICs were called third generation.


At the start of the 1970s, a Japanese calculator firm approached Intel to design them a set of ICs for a calculator. The result of this was the first microprocessor, the 4004, and the first RAM chip. The 4004, a four-bit chip, was followed shortly by eight-bit chips, the 8008 and the 8080. Thus, fourth generation computers were born.

The 8008 chip with 60,000 transistors
The 8008 microprocessor
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