Page 42 - A Practical Guide from Design Planning to Manufacturing

18 Chapter One

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months. This trend has come to be known as Moore’s law. For micro-
processors, the trend has been closer to a doubling every 2 years, but
amazingly this exponential increase has continued now for 30 years
and seems likely to continue through the foreseeable future (Fig. 1-7).
The 4004 used transistors with a feature size of 10 microns (µm).
This means that the distance from the source of the transistor to the
drain was approximately 10 µm. A human hair is around 100 µm across.
In 2003, transistors were being mass produced with a feature size of only
0.13 µm. Smaller transistors not only allow for more logic gates, but also
allow the individual logic gates to switch more quickly. This has provided
for even greater improvements in performance by allowing faster clock
rates. Perhaps even more importantly, shrinking the size of a computer
chip reduces its manufacturing cost. The cost is determined by the cost
to process a wafer, and the smaller the chip, the more that are made from
each wafer. The importance of transistor scaling to the semiconductor
industry is almost impossible to overstate. Making transistors smaller
allows for chips that provide more performance, and therefore sell for
more money, to be made at a lower cost. This is the fundamental driving
force of the semiconductor industry.

Intel processor transistor count
1,000,000
Pentium D
Pentium 4 EE
100,000 Pentium II Pentium 4
Number of transistors (K) 10,000 80286 i486DX Pentium Pentium III

Pentium pro
1000

80386DX
100

10 8088 Processor transistor count doubles every 2 years
8008 8085
8080
4004
1
1970 1975 1980 1985 1990 1995 2000 2005
First year shipping
Figure 1-7 Moore’s law. (Moore, “No Exponential is Forever,” 10.)

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Moore, “Progress in Digital Integrated Electronics.”