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8/7/2019 Introduction of Microprocessor
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Introduction:
A Microprocessor incorporates most or
all of the functions of a computer's central
processing unit (CPU) on a single
integrated circuit (IC, or microchip). The
first microprocessors emerged in the early
1970s and were used for electronic
calculators, using binary-coded decimal
(BCD) arithmetic on 4-bit words. Other
embedded uses of 4- bit and 8-bit
microprocessors, such as terminals,
printers, various kinds of automation etc.,
followed rather quickly. Affordable 8-bit
microprocessors with 16-bit addressing
also led to the first general purpose
microcomputers in the mid-1970s.
Computer processors were for a long
period constructed out of small andmedium-scale ICs containing the
equivalent of a few to a few hundred
transistors. The integration of the whole
CPU onto a single chip therefore greatly
reduced the cost of processing capacity.
From their humble beginnings, continued
increases in microprocessor capacity have
rendered other forms of computers almost
completely obsolete, with one or more
microprocessor as processing element in
everything from the smallest embedded
systems and handheld devices to the
largest mainframes and supercomputers.
Evolution of Microprocessors:
In Early days microprocessor can be
defined as ³a computer processor that is
contained on an integrated chip´. In other
words we can say a microprocessor is a
central processing unit contained on a
large scale integration chip.The
microprocessor has changed the way
computers work by making them faster.
The microprocessor is often called the
brain of the C.P.Uand without the
microprocessor the computer is more or
less useless.
Microprocessor technology is progressing
so rapidly that even experts in the field are
having trouble keeping up with current
advances.
Figure 1: Intel 4004 Microprocessor
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What l t the devel ent of
Mi oprocessors?
Microprocessors essentiall evolved from
mechanical relays to integrated circuits. It is impor tant to illustrate here what aspects
of the computing industry that led to the
development of microprocessors.
a) Digital Computer Technology:
Advancement of Digital Computer
Technology by developing new
computers with high processing speed,
smaller in size & less expensive in late
1940¶s.
b) Semiconductors:
Semiconductors had also been growing
steadily since the invention of the
transistor in the late 1940s. In 1960s,
invention of integrated circuit lead us
to develop from just a few transistors
to many complicated tasks, allof them
on the same chi p.
The development of microprocessors can
be attr i buted to when, in the ear ly 1970s,
digital computers and integrated circuits
reached the required levels of capability.
However, the ear ly microprocessor did not
meet all the goals: it was too expensive for
many applications, especially those in the
consumer market, and it could not hold
enough information to perform many of
the tasks being handled by the
minicomputers of that time.
Generations of Microprocessor :
y FIRST-GENERATION:
The microprocessors that were
introduced in 1971 to 1972 were
referred to as the f irst generation
systems. They fetched the instruction,
decoded it, and then executed it.When
the execution was completed then it its
instruction pointer was updated to
fetch next instruction.
Figure 2: INTEL C8080A Mi
The Intel 8080 was an ear ly
microprocessor designed and
manufactured by Intel. The 8-bit
microprocessor was released in Apr il
1974 running at 2 MHz (at up to
500,000 instructions per second), and
is sometimes considered to be the f irst
truly usable microprocessor.The 8080
was implemented using non-saturated
enhancement-load NMOS, demanding
extra voltages.
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y SECOND GENERATION:
In 1973, enough transistors were
available on the IC containing: 16-bit
ar ithmetic and pi pelined instruction
processing.
The distinction between the f irst and
second generation devices was
pr imar ilythe use of newer
semiconductor technology to fabr icate
the chi ps. This new technology
resulted in a f ive-fold increase in
instruction, execution, speed,
andhigher chi p densities.
For Example:
Motorola¶s MC68000, microprocessor
introduced in 1979, is an example.
Another example is Intel¶s 8080. This
makes the use of semiconductor
technology.
Figure 3: Motorola MC68000 Mi
roprocessor
y THIRD GENERATION:
It was introduced in 1978 represented
by Intel 8086 having 16 bit processor
like minicomputer like performance. It
consists of single chi p cache.The third
generation came about as IC transistor
counts approached 250,000.This
generation ofmicroprocessors was
different from the previous ones in that
all major workstationmanufacturers
began developing their own RISC-
based microprocessor architectures
were introduced.
For Examples:
Intel¶s 8086/80186/80286, Motorola¶s
68000/68010& AMD 486c
Figure 4: Intel 8086 Microprocessor
The 8086 is a 16-bit microprocessor
chi p designed by Intel, which gave r ise
to the x86 Architecture. Intel 8086
microprocessor is also called iAPX86.
The development work on the 8086
design star ted in 1976 and the chi p was
introduced in the market in 1978.
y FOURTH GENERATION:
As the workstation companies
conver ted from commercial
microprocessors to in-house designs,
microprocessors entered their four th
generation with designs surpassing a
million transistors.
This era marked with the beginning of
32 bits microprocessors.
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For Example:
Microprocessors such as Intel¶s
80960CA and Motorola¶s 88100 could
issue and retire more than one
instruction per clock cycle.
Figure 5:Intel 80960 Microprocessor
The 80960 (i960CA) was the f irst pure
RISC implementation of the i960
architecture. It featured a newly-
designed superscalar RISC core and
added an unusual addressable on-chi p
cache, but lacked an FPU and MMU,
as it was intended for high-
performance embedded applications.
The i960CA is widely considered to
have been the f irst single-chi p
superscalar RISC implementation. The
C-ser ies only included one ALU, but
could dispatch and execute an
ar ithmetic instruction, a memory
reference, and a branch instruction at
the same time, and sustain two
instructions per cycle under cer tain
circumstances. The i960CA
microarchitecture was designed in
1987±1988 and formally announced on
1989. Later, the i960CF included a
f loating-point unit, but continued to
omit an MMU.
y FIFTH GENERATION:
Microprocessors in their f if th
generation, employed decoupled super
scalar processing, and their design
soon surpassed 10 million transistors.
In this generation, PCs are a low-
margin, high-volume-business
dominated by a single microprocessor.
For Examples:
Intel leads the show here with Pentium,
Celeron and very recently dual and
quad core processors work ing with up
to 3.5GHz speed.
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Figure 6: Intel Core i7 Microprocessor
Basic Architecture of Microprocessor :
Figure 7: Basic Architecture of Microprocessor
The block diagram shows the basic
architecture of a microprocessor based
system. In this system, the microprocessor
is the master and all other per i pherals are
slaves. The master controls all the
per i pherals and initiates all operations.
The microprocessor is the functional
center of the microcomputer system.
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Its internal construction can be broadly
divided into three sections:
y Control section
y Ar ithmetic and Logic Unit
y Register section
y System Bus
Control Section:
Control section/unit is the par t of the
microcomputer that controls its basic
operations. It is made up of the control
signal generating circuitry (clock) and thecommand (instruction) decoder.
The control section fetches pre-
programmed instructions from memory
(op-code fetch cycle) as needed and
temporar ily stores them in the command
register (also known as Instruction
Register IR).
These instructions are then decoded by the
operation decoder (decode cycle), which
sends control signals to the relevant par ts
of the microcomputer system (via the
system busses) to cause them to carry out
the required operation (execute cycle).
The timing with which these control
signals are generated is determined by the
clock. The number of T-states tells the
time taken for the CPU to execute that
par ticular instruction.
The major types of operations controlled
by the control signals are :-
a) Sending of data from one par t of the
microcomputer to another (read or wr ite
cycle).
b) Inputting and out putting of data to/from
the microcomputer (I/O read or wr ite
cycle).
c) Ar ithmetic and Logic calculations.
d) Halting of computer instructions.
e) Jumping to another instruction dur ing
running (execution) of a program.
Ar ithmetic and Logic Unit:
Ar ithmetic and Logic Unit comes under
the control of control section carr ies out
the actual processing of data, normally
descr i be as data mani pulation. This
consists largely of ar ithmetic operations
(ADDition, SUBtraction, INCrementing,
DECrementingetc) and logical operations
(ANDing, OR ing, XOR ing, NOTingetc).
The ALU carr ies out these operations in
the following manner :
1) Stores data fetched from memory or I/O
in the registers.
2) Fetches this data as needed from the
registers and/or from relevant
accumulators.
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3)Send this data either to its ar ithmetic
circuitry or logical circuitry, where
necessary, where the necessary, ar ithmetic
or logical operations are carr ied out.
4) Send results of its ar ithmetic or logical
operation to relevant accumulator, to the
memory, or to the I/O interfaces.
Register Section:
The register section/array consists
completely of circuitry used to temporar ily
store data or program codes until they are
sent to the ALU or to the control section or
to memory. The number of registers are
different for any par ticular CPU, and the
more register a CPU have will result in
easier programming tasks.
System Bus:
The three components of the
microcomputer system is connected by
three busses, also known as System Bus.
These busses is used to transfer
information (data) internally and
externally to the microprocessor.
a) Address Bus
The address bus is 'unidirectional',
over which the microprocessor sends
an address code to the memory or
input/out put.
The size (width) of the address bus is
specif ied by the number of bits it can
handle.
The more bits there are in the address
bus, the more memory locations a
microprocessor can access. A 16 bit
address bus is capable of addressing
65,536 (64K) addresses.
b) Data Bus:
The data bus is 'bi-directional', on
which data or instruction codes are
transferred into the microprocessor or
onwhich the result of an operation or
computation is sent out from the
microprocessor to the memory or
input/out put.
Depending on the par ticular
microprocessor, the data bus can
handle 8 bit or 16 bit data.
c) Control Bus:
The control bus is used by the
microprocessor to send out or receive
timing and control signals in order to
coordinate and regulate its operation
and to communicate with other
devices, i.e. memory or input/out put.
The lines used to control memory and
I/O devices are MEMRQ*, IORQ*,
RD* and WR*. Others are general
Control signals to handle special
external requests (interrupts), special
I/O devices (DMA) and special k ind
of Memory (DRAM).
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Performance of Microprocessors :
The number of transistors available has a
huge effect on the performance of
aprocessor. With more transistors, much
more powerful multi pliers capable of
single-cycle speeds become possi ble.
More transistors also allow a technology
called pi pelining. In a pi pelined
architecture, instruction execution
over laps.
For example:
A microprocessor might take 5 clock
cycles to execute each instruction, there
can be 5 instructions in var ious stages of
execution simultaneously, i.e. eachone
instruction completes in every clock cycle.
Many modern processors have multi ple
instruction decoders, each with its own
pi peline. This allows multi ple instruction
streams, which means more than one
instruction can complete dur ing each clock
cycle. This technique can be quite complex
to implement, so it takes lots of transistors.
The trend in processor design has been
toward full 32-bit ALUs with fast f loating
point processors built in and pi pelined
execution with multi ple instruction
streams. There has also been the addition
of hardware vir tual memory suppor t and
L1 caching on the processor chi p. All of
these trends push up the transistor count,
leading to the multi-million transistor
powerhouses available today.
Three basic character istics stand out:
y Instruction Set: The set of instructions
that the microprocessor can execute.
y Bandwidth: The number of bits
processed in a single instruction.
y Clock Speed: Given in megaher tz
(MHz), the clock speed determines
howmany instructions per second the
processor can execute.
In addition to bandwidth and clock speed,microprocessors are classif ied as being
either RISC (reduced instruction set
computer) or CISC (complex instruction
set computer).
Break through in Microprocessor :
y In ear ly 1940¶s the switching unit were
used as a mechanical relays that are
capable of performing calculations.
y In 1950¶s vacuum tubes were used.The
Atanasoff berry computer was mak ing
use of vacuum tubes a s their switching
device as they can perform calculations
much more faster and in eff icient way
than relay machines.
y Then there comes transistor in
1960¶sthat br ing revolution in the
whole scenar io. It changed the
computer from a giant electronic brain
to a simple commodity like a TV.This
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led to the development of the
Minicomputers.
y Then there comes a concept called
³integrated circuit . Intergraded chi ps
are tiny silicon chi ps and are used in
aerospace and for military purposes.
But at that time only big companies
were able to afford this.
y Later on more sophisticated chi p was
introduced and was termed as
³Microprocessor¶.The Microprocessor
is the extension of Ar ithmetic and
Logical unit that is able to extract data
from the memory and interpret it as an
instruction.The term was f irstly
introduced by the Intel in 1972.
y In 1980¶s full scale microprocessor
were developed that consists of 32 bit
address system and has operating
frequency is from 25 to 50 Mhz.
Microprocessors Today:
Technology has been changing at a rapid
pace. Everyday a new product ismade to
make life a little easier. The computer
plays a major role in the lives of
most people. It allows a person to do
practically anything. The Internet enables
the user togain more knowledge at a much
faster pace compared to researching
throughbooks. The por tion of the computer
that allows it to do more work than a
simplecomputer is the Microprocessor.
Microprocessor has brought electronics
into a new era and causedcomponent
manufacturers and end-users to rethink the
role of the computer. Whatwas once a
giant machine attended by specialists in a
room of its own is now a tinydevice
conveniently transparent to users of
automobile, games, instruments,
off iceequi pment, and a large array of other
products.
From their humble beginnings 25 years
ago, microprocessors haveproliferated into
an astounding range of chi ps, power ing
devices ranging fromtelephones to
supercomputers.
Today, microprocessors forpersonal
computers get widespread attention and
have enabled Intel to becomethe wor ld's
largest semiconductor maker. In addition,
embedded microprocessorsare at the hear t
of a diverse range of devices that have
become staples of aff luentconsumers
wor ldwide.
The impact of the microprocessor,
however, goes far deeper than new
andimproved products. It is alter ing the
structure of our society by changing howwegather and use information, how we
communicate with one another, and how
andwhere we work. Computer users want
fast memory in their PCs, but most do
notwant to pay a premium for it.
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Bi bliography:
Books Referred:
y Fundamentals of Microprocessors and
Microcomputers by B. Ram
y Microprocessor and Assembly Language
Programming by U. S Shah
Internet Sites:
y www.google.com
y www.ask.com
y www.wik i pedia.com