Page 26 - A Practical Guide from Design Planning to Manufacturing

2 Chapter One

It is the processor that determines what action will happen next within
the computer and directs the overall operation. Processors in early
computers were created out of many separate components, but as tech-
nology improved it became possible to integrate all of the components
of a processor onto a single piece, or chip, of silicon. These integrated
circuits are called microprocessors.
Today microprocessors are everywhere. Supercomputers are designed
to perform calculations using hundreds or thousands of microprocessors.
Even personal computers that have a single central processor use other
processors to control the display, network communication, disk drives, and
other functions. In addition, thousands of products we don’t think of as
computers make use of microprocessors. Cars, stereos, cell phones,
microwaves, and washing machines all contain microprocessors. This
book focuses on the design of largest and most complex microprocessors,
which are used as the central processing units of computers, but what
makes processors so ubiquitous is their ability to provide many different
functions.
Some computer chips are designed to perform a single very specific
function, but microprocessors are built to run programs. By designing
the processor to be able to execute many different instructions in any
order, the processor can be programmed to perform whatever function
is needed at the moment. The possible uses of the processor are limited
only by the imagination of the programmer. This flexibility is one of the
keys to the microprocessor’s success. Another is the steady improve-
ment of performance.
Over the last 30 years, as manufacturing technologies have improved,
the performance of microprocessors has doubled roughly every 2 years. 1
For most products, built to perform a particular function, this amount
of improvement would be unnecessary. Microwave ovens are an improve-
ment on conventional ovens mainly because they cook food more quickly,
but what if instead of heating food in a few minutes, they could be
improved even more to only take a few seconds? There would probably
be a demand for this, but what about further improvements so that it
took only tenths of a second, or even just hundredths of a second.
At some point, further improvements in performance of a single task
become meaningless because the task being performed is fast enough.
However, the flexibility of processors allows them to constantly make
use of more performance by being programmed to perform new tasks.
All a processor can do is run software, but improved performance makes
new software practical. Tasks that would have taken an unreasonable
amount of time suddenly become possible.

1
Moore, “No Exponential is Forever,” 20.