Bell Labs Technical Journal
The microprocessor, which evolved from the
inventions of the transistor and the integrated circuit
(IC), is today an icon of the information age. The per-
vasiveness of the microprocessor in this age goes far
beyond the wildest imagination at the time of the first
microprocessor. From the fastest computers to the
simplest toys, the microprocessor continues to find
The microprocessor today represents the most
complex application of the transistor, with well over
10 million transistors on some of the most powerful
microprocessors. In fact, throughout its history, the
microprocessor has always pushed the technology of
the day. The desire for ever-increasing performance
has led to the rapid improvements in technology that
have enabled more complex microprocessors.
Advances in IC fabrication processes, computer archi-
tecture, and design methodologies have all been
required to create the microprocessor of today.
As we trace the history of the microprocessor,
we will explore its evolution and the driving
forces behind this evolution. In the earliest
stages, microprocessors filled the needs of embed-
ded applications. It was not long, however,
before advances in microprocessors and comput-
ers drove the capabilities and needs of both. We
will discuss these and other forces behind the
history of the microprocessor, including the
impact of individuals and companies.
The history of the microprocessor can be divided
into five stages:
• The birth of the microprocessor,
• The first microcomputers,
• A leading role for the microprocessor,
• The promise of reduced instruction set com-
puter (RISC), and
• Microprocessors of the 1990s.
These five stages define a rough chronology, with
some overlap. Each stage could be said to reflect a
generation of microprocessors, with corresponding
generations of applications. For each stage, we discuss
representative microprocessors and their key applica-
tions. Figure 1 shows a timeline of the development
of the microprocessor, starting with the Intel * 4004.
The information in this paper was taken from
many sources, including other overviews of the his-
tory of the microprocessor.
We have selected the
microprocessors discussed in this paper based on their
innovation and their success in the marketplace.
Embedded processors are given limited coverage since,
in many cases, the microprocessors mentioned in
more detail have led to versions for embedded applica-
tions. We have not covered digital signal processors
(DSPs), even though they could be considered a type
of microprocessor. However, we have included in the
appendix of the paper a history of microprocessors at
Bell Labs, which has designed microprocessors since
the latter half of the 1970s.
♦ The History of the Microprocessor
Michael R. Betker, John S. Fernando, and Shaun P. Whalen
Invented in 1971, the microprocessor evolved from the inventions of the transistor (1947) and the integrated circuit (1958). Essentially a computer on a chip, it is the most advanced application of the transistor. The influence of the microprocessor today is well known, but in 1971 the effect the microprocessor would have on every- day life was a vision beyond even those who created it. This paper presents the his- tory of the microprocessor in the context of the technology and applications that drove its continued advancements.
Copyright 1997. Lucent Technologies Inc. All rights reserved.
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Bell Labs Technical Journal
The Birth of the Microprocessor
"Announcing a New Era of Integrated Electronics"
-Headline, Intel 4004 ad
The history of the microprocessor begins with the
birth of the Intel 4004, the first commercially available
microprocessor (see Panel 2). The roots of this devel-...