Microprocessors

1. Jonathan Stanley
EET230: Digital Systems II
Jeevan D’Souza
07/16/2015
Microprocessors
While growing up I’ve always been interested in electronics, preferably computers. At
age nine my household had gotten its first desktop computer which immediately struck my
interest. Over time however, the electronics I had grown to love started to become smaller,
thinner, and sleeker, as well as providing more functionality. Along with this, newer electronics
started to make their way into society. When I received my first desktop computer, I would have
never dreamed that one day these things would become portable and weigh no more than five
pounds and be in the millimeter range of thickness. I also would have never dreamed that one
day all of the electronics that I grew to love would one day fit inside of a phone that was the size
of the average man’s wallet. In my younger years I had no idea how manufacturers were able to
do what they did in making electronics smaller and smaller. My mind could not even fathom
how a room full of yesterday’s technology could fit into a single device of tomorrow. I began to
look further and more in depth at everyday electronics, taking them apart, looking inside to see
what made them tick, and putting them back together. I noticed how every circuit board
contained small chips, and the newer the device was, the more chips that were inside of it. I
began to realize that that is how these devices were capable of becoming so much smaller. It
seemed that every circuit board was being replaced with tiny chips that could perform all of the
functions necessary for every single electronic device to work. So what was in fact a CPU that fit

2. into the average computer or computer-like device in that time, had now became something
known as a microprocessor which could range in sizes from a fingernail to a USB drive. When I
started college, microprocessors started to become more and more familiar and I could see their
applications everywhere. I began to build circuits with beginner level microprocessors, such as
light indicating 555 timer circuits, laser pointer sensing circuits, and even small cars that relied
on micro-processing chips to move and turn different directions when a certain path was no
longer available. For this research paper, I have decided to look further into microprocessors. I
will be researching various subtopics on these microprocessors and finding most of my research
through credible online sources. The research I plan to conduct on these microprocessors include
what they are, what they do, their structure, the history of them and how they came to light, etc.
Basically I am looking for any interesting research that will further my knowledge of these
microprocessors that are the heart of every computer-like device that we know and love today.
A microprocessor can be many varying definitions according to where you look, but the
most basic definition is that it is a ”multipurpose, programmable digital integrated circuit that
can be programmed with a series of instructions to implement various operations on data. It is
basically the CPU of a computer and can perform actions such as arithmetic, logic operations,
move data from one place to another, and make decisions based on a set of given instructions, all
within a single microchip” (Floyd, 2006, p. 824). “These microprocessors use sequential digital
logic as they have internal memory and operate on numbers and symbols represented in the
binary numeral system” (Future Electronics). Upon further reading on these devices, I found that
a microprocessor consists of several units. Each of these units have their own specific job and
duties that it carries out. All in all, each unit along with their design and how they are organized,
is known as the microprocessors architecture. Most, if not all microprocessors consists of four

3. basic units which include the arithmetic logic unit (ALU), the instruction decoder, the register
array, and the control unit. The ALU part of the microprocessor is known as the key processing
element. “It is directed by the control unit to perform arithmetic operations such as addition,
subtraction, multiplication, and division. Along with this, it can also perform logic operations
such as NOT, AND, OR, and exclusive-OR, as well as many other types of operations that may
need to be performed. Data that is used by the ALU is obtained from the register array” (Floyd,
2006, p. 824). The instruction decoder is usually considered to be a part of the ALU, although
some treat it as a separate unit due to the instructions and the decoding of them being the key to a
microprocessor’s operation. “The microprocessor accomplishes a given task as directed by
programs that consists of lists of instructions stored in memory. The instruction decoder takes
each binary instruction in the order in which it appears in memory and decodes it” (Floyd, 2006,
p. 824). Following this, the register array is just a collection of registers that are placed within a
microprocessor. I learned that these register arrays are basically used as temporary storage
devices for the microprocessor to store data and memory addresses during a program’s
execution. The ALU can then access the data within the registers very quickly so that the
program can run smoothly and more efficiently. Upon further reading, I found that registers can
be classed into different groups. One of which is known as a general purpose register, which
means that it can be used for any purpose that the program might need it for. Other registers on
the other hand may have specific capabilities and functions and cannot be used like the general
purpose ones. There are also registers that are known as program invisible registers, which are
strictly only used for the microprocessor while being unavailable to the programmer. Lastly, the
control unit is the part of the microprocessor that is in charge of the processing and instructions
once they are decoded. It can provide the timing and the control signals for getting data in and

4. out of the microprocessor, as well as synchronizing the execution of the instructions. Altogether,
the basic operation that includes each unit of the microprocessor can be simplified into three
steps. “First it will fetch an instruction from memory and place it in the CPU. Secondly, the
instruction will then be decoded, along with fetching any additional information specified by the
instruction. The program counter is also updated to point to the next instruction in this step.
Thirdly, the instruction is then executed and the results are returned to the registers and memory”
(Floyd, 2006, p. 827). After I had found out about the basic operation and architecture of the
microprocessor, I began to wonder just how many devices in the world today use them.
Anywhere you look in today’s society, there is some kind of device that uses digital data as input
to provide a specific output, since everything seems to be switching to digital rather than analog.
I was amazed at what I found as to how many applications use a microprocessor. I read that “as a
general purpose, some microprocessors in PCs are used for displaying multimedia, computation,
text editing, and communication, while others can be part of an embedded system to provide
digital control to various devices such as common household appliances, vehicles and their
equipment, media players, toys, electrical circuit breakers, light switches, smoke alarms, car
keys, power tools, and even the average cell phone (Future Electronics). After realizing how all
of these applications work every day you use them, I began to become familiar with how
microprocessors play a role in each one. After learning about the various applications that use
microprocessors, I began to wonder how they came to light. I wanted to know who created the
first one, how complex was it, and how did they grow into the powerful microchips that we
know today. I found that before the microprocessor was developed, there existed a variety of
early technology that could simulate logic functions in computing devices, and that a lot of this
early technology was spurred by wartime needs during World War II. Like anything however,

5. this old technology was very expensive, slow, and prone to failure, compared to what we have
today. This technology was based on vacuum tubes and transistors made by IBM who was a
giant in the computing industry back then. However, the technology from IBM was not suitable
for home or business use due to their costs and the required maintenance that needed to be done
to keep them going. In 1968 though, a company known as Intel was created and became known
as the company that invented the microprocessor in 1971. An interesting fact I found however,
was that Intel only “invented the term microprocessor, and that in fact an earlier 8-bit chip which
was the Four-Phase Systems AL1 was invented in 1969 as part of a multi-chip CPU. It was not
called a microprocessor though until a court case in the 1990’s where it was demonstrated that
the AL1 could function as the core of a computer” (Kitchen Table Computers, 2014). For all
points and purposes however, the computer age did not begin until Intel’s first microprocessor,
which contained as much processing power as the most powerful computer that existed in the
entire world at that time. Intel introduced this first microprocessor as the Intel 4004, which was a
4-bit chip. “This chip was a 1/8” by 1/16” microchip that contained 2,300 transistors etched onto
the silicon and all by itself, was more powerful than the earliest computer known as ENIAC built
in 1946 that weighed about thirty tons” (PBS 1999). The 4004 however, was quickly succeeded
by the Intel 8008, which was an 8-bit chip, just a short year later. Being that the 8008 had double
the bits, it was twice as powerful. “In 1978, Intel released the 16-bit 8086 processor and the
8088, which was also a 16-bit chip following less than a year later. The 8088 chip incorporated
technologies designed to make it backward-compatible with the 8-bit chips that were still in wide
use at that time, and it is the same chip that IBM chose to power their original PC” (Kitchen
Table Computers, 2014). After all of this technology started going mainstream, it was IBM,
Intel, and a small startup company known as Microsoft that began to bring computing to

6. everyone around the world. I found upon further reading however, than Intel did not stop there,
and that in the early 1990’s they released the i386 processor which was the first commercially
available 32-bit microprocessor. This specific microprocessor made it possible to multitask on
desktop computers, meaning that you could run more than one program and a time. After this,
they produced the i486, which added an onboard math co-processor, better and faster data
transfer, and an onboard memory cache, which were all considered amazing technological
advances in that day and time. “Then in 1993, the Intel Pentium processor was released, which
was a microprocessor capable of executing two instructions for every clock cycle. The later
microprocessors in the Pentium line defined everything from the way data is moved about on
microchips to the way that multimedia content is handled” (Kitchen Table Computers). Intel’s
latest and greatest however, is the line of multi-core, 64-bit processors, such as the Core series,
which had capabilities that were unheard of only a few years ago. Since these microprocessors
have become well known, there were a number of other companies who created their own lines
of microprocessors, in which some succeeded, and some not so much. All in all though, Intel’s
discoveries and technological advances made it possible to perform the everyday duties that we
see ourselves doing every day, when it comes to computers and other digital devices.
Overall, the research that I had conducted has taught me a lot about microprocessors. I
learned a great deal these small devices, including what they are, what they do, how they operate,
their applications, and the history of the first microprocessor to today. Microprocessors are
basically a digital integrated circuit on a single chip that performs the actions of the CPU of any
computing device available. The actions of this digital circuit include arithmetic, logic, move
data, and make decisions based on specific instructions defined. All of the functions that a
microprocessor can do are made possible by the four units that make of this small device. These

7. four units include the arithmetic logic unit (ALU), the instruction decoder, the register array, and
the control unit. Each basic unit of the microprocessor performs a specific job and duty that
make the device as a whole capable of doing what it does. Due to the microprocessor being such
a great and powerful device in what it does, it is used in a various amount of applications that we
see every day without realizing it. Some basic applications for these devices include common
household appliances, vehicles, electrical circuit breakers, toys, televisions, computers, and many
more. What interested me the most in my research is the history of the microprocessor however.
I was amazed by the fact that the first ever microprocessor, known as the Intel 4004, was more
powerful than the biggest computer in the world that weighed in at a surprising thirty tons,
known as ENIAC. It was hard to believe that 2,300 transistors were able to be etched on to this
single silicon chip and although less than a quarter of an inch thick and wide, it would have more
functionality than this thirty ton computer. Over time, microprocessors became smaller, better,
and were able to perform more than we could imagine. These tiny devices are the keystone to the
technology we have in today’s society and made it possible to perform the everyday duties that
we accomplish with computing devices on a global scale. It’s a little hard to fathom that all of
this was made possible by an idea in the hands of the right people, and a few companies that
wanted to make a change.

8. References
1) Floyd, T. L. (2006) Digital Fundamentals with PLD Programming. Upper Saddle River,
New Jersey: Prentice Hall.
2) Future Electronics. What is a Microprocessor?. Retrieved from https://www.futureelectro
nics.com/en/Microprocessors/microprocessors.aspx
3) Kitchen Table Computers. (2014) Microprocessor History and Background. Retrieved
from http://www.kitchentablecomputers.com/processor.php
4) PBS Online. (1999) Invention of the Microprocessor. Retrieved from http://www.pbs.org/
transistor/background1/events/micropinv.html