Microcomputer Circuits and Processes

transistor, through the logic circuits of 1965 and the 4096-transistor
memory of 1971, to the 4 million-bit 'bubble' memory introduced in
1982. Of course the rate of doubling has slowed recently, but there is
still anticipation of further miniaturization.
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Figure 1.1
Graph showing 'Moore's Law' - the doubling of number of transistors per Ie per year.
The 4-megabit bubble memory introduced in 1982 does not use transistor technology.
As any industry grows and gains experience its production costs fall,
but the IC industry has been unique in achieving a constant doubling in
component density coupled with falling costs. How has this been
achieved? It is due to the IC concept, replacing transistor-based circuits
in traditional equipment, producing smaller, more reliable, easily
assembled devices. Much of the success of the IC industry has come
from stimulating new markets. A good example is computer memory.
Up to the end of the 1960s, computer memory was made from small
rings of magnetic material sewn together by electrical wires. It worked,
but compared with the component densities being achieved in the IC,
the package was bulky. People in the semiconductor industry realized
this, and understood that the requirements of computer memory - a
large number of storage cells connected with a small number of leads -
could be met by specially designed IC chips. Companies were founded
with the sole purpose of memory manufacture, and as miniaturization
continued and prices fell, semiconductor memory became established as
the standard. Thanks to these devices, the large, room-sized computers
of the 1950s and 1960s, with their hundreds of kilometres of wiring,
could be made smaller and more powerful. The mainframe and
minicomputers were born.
2