lecture 1 introduction to computerarchtecture

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Lecture 1: Introduction to Computer Architecture

The aim of this course unit is to present the nature and characteristics of modern-day computer

systems. This task is challenging for several reasons:

1. There is a tremendous variety of products that can rightly claim the name Computer, from

single-chip microprocessors to supercomputers. Variety is exhibited in terms of cost, size,

performance and application.2. The rapid pace of change that has always characterised computer technology continue with

no letup e.g integrated circuit (IC) used to construct computer components, increased use

of parallel organisation concepts in combining those components and many ore aspects of

computer technology.

In spite of the variety and pace of change, certain fundamental concepts apply throughout. The

application of these concepts depends on the current state of technology and price/performance

objectives of the designer.All of the basic performance characteristics of computer systems, including processor speed,

memory speed, memory capacity, and interconnection data rates, are increasing rapidly.

This makes it difficult to design a balanced system that maximises the performance and

utilisation of all elements. Thus, computer design is a game of changing the structure or

function in one area to compensate for a performance mismatch in another area.

A computer system consists of an interrelated set of components. The system is best

characterised in terms of structure the way in which components are interrelated, and

function the operating of the individual components.

Why Study Computer organisation and Architecture?

The IEEE/ACM (Institute of Electrical and Electronics Engineers/Association for Computing

Machinery) report (2001) lists computer architecture as one on the core subjects that should be

in the curriculum of all students in Computer Science and Computer Engineering.

The report says the following:

The computer lies at the heart of computing. Without it most disciplines today would be

a branch of theoretical mathematics. To be a professional in the field of computing

today, one should not regard the computer as just a black box that executes programs by

magic. All students of computing should acquire some understanding and appreciationof a computer systems functional interactions. There are practical implications as well.

Students need to understand computer architecture in order to structure a program so that

it runs more efficiently on a real machine. In selecting a system to use, they should beable to understand the tradeoff among various components, such as CPU clock speed

versus memory size.

The following examples are reasons for studying computer architecture:

1. Suppose a graduate enters the industry and is asked to select the most effective

computer for use throughout a large organisation. An understanding of theimplications of spending more for various alternatives, such as a larger cache or a

higher processor clock rate, is essential to making the decision.

2. Many processors are not used in PCs or servers but in embedded systems. A designer

may program a processor in C that is embedded in some real-time or larger system,

such as intelligent automobile electrics controller. Debugging the system may require

the use of a logic analyser that displays the relationship between interrupt requests

from engine sensors and machine-code.

3. Concepts used in computer architecture find application in other courses. In particular,the way in way in which the computer provides architectural support for programming

languages and operating system facilities reinforces concepts from those areas.

Computer Architecture and Organisation

Definition of terms

a) Computer Architecture

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Baer: The design of the integrated system which provides a useful tool to the programmer

Hayes: The study of the structure, behavior and design of computers

Abd-Alla: The design of the system specification at a general or subsystem level

Foster: The art of designing a machine that will be a pleasure to work with

Hennessy and Patterson: The interface between the hardware and the lowest level software

Common themes: Design / structure

Art

System

Tool for programmer and application

Interface

Thus, computer architecture refers to those attributes of the system that are visible to a

programmer those attributes that have a direct impact on the execution of a program

Instruction sets Data representations the number of bits used to represent various data types ()e.g. numbers,

characters, etc)

Addressing memory techniques.

I/O mechanisms

NB

Computer architects have always been striving to increase the performance

of their architectures.Computer architecture is concerned with the structure and behavior of the computer as seen by

the user. It includes the information formats, the instruction set, and techniques for addressing

memory. The architectural design of a computer system is concerned with the specifications of

the various functional modules, such as processors and memories, and structuring them together

into a computer system.

Computer design is concerned with the hardware design of the computer. Once the computerspecifications are formulated, it is the task of the designer to develop hardware for the system.

Computer design is concerned with the determination of what hardware should be used and

how the parts should be connected. This aspect of computer hardware is sometimes referred to

as computer implementation.

b) Computer OrganizationComputer Organization refers to the operational units and their interconnections that realize thearchitecture specifications.

Synonymous with architecture in many uses and textbooks. We will use it to mean the

underlying implementation of the architecture, transparent to the programmer.

An architecture can have a number of organizational implementations:

Control signals

Technologies

Device implementations

Computer organization is concerned with the way the hardware components operate and the

way they are connected together to form the computer system. The various components are

assumed to be in place and the task is to investigate the organizational structure to verify thatthe computer parts operate as intended.

Structure & Function

A hierarchical system is a set of interrelated subsystems, each of the latter, in turn,

hierarchical in structure until we reach some lowest level of elementary subsystem.

Structure is the way in which components relate to each other

Function is the operation of individual components as part of the structure

c) Computer

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A computer is an electronic machine that accepts information, stores it until the information is

needed, processes the information according to the instructions provided by the user, and finally

returns the results to the user. The computer can store and manipulate large quantities of data at

very high speed, but a computer cannot think. A computer makes decisions based on simple

comparisons such as one number being larger than another. Although the computer can help

solve a tremendous variety of problems, it is simply a machine. It cannot solve problems on its

own!!!

Historically, a computer was a job title, not a piece of equipment!

Requirements of a computer are:

Process data

Store data

Move data between the computer and the outside world

Control the operation of the above

Figure showing functional view of a computer

History of ComputersTECHNOLOGICAL DEVELOPMENTComputer technology has shown an unprecedented rate of improvement. This includes the development of

processors and memories. Indeed, it is the advances in technology that have fueled the computer industry.The integration of numbers of transistors (a transistor is a controlled on/off switch) into a single chip has

increased from a few hundred to millions. This impressive increase has been made possible by the advancesin the fabrication technology of transistors.The scale of integration has grown from small-scale (SSI) to medium-scale (MSI) to large-scale (LSI) tovery large-scale integration (VLSI), and currently to wafer-scale integration (WSI). Table 1 shows the

typical numbers of devices per chip in each of these technologies.

TABLE 1 Numbers of Devices per Chip

It should be mentioned that the continuous decrease in the minimum devices feature size has led to acontinuous increase in the number of devices per chip, which in turn has led to a number of developments.Among these is the increase in the number of devices in RAM memories, which in turn helps designers totrade off memory size for speed. The improvement in the feature size provides golden opportunities for

introducing improved design styles.

Mechanical Era (1600s-1940s)

Wilhelm Schickhard (1623) Astronomer and mathematician

Automatically add, subtract, multiply, and divide

Blaise Pascal (1642)

Mathematician

Mass produced first working machine (50 copies)

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Could only add and subtract

Maintenance and labor problems

Gottfried Liebniz (1673)

Mathematician and inventor

Improved on Pascals machine

Add, subtract, multiply, and divide

Charles Babbage (1822)

Mathematician Father of modern computer

Wanted more accuracy in calculations

Difference engine

Government / science agreement

Automatic computation of math tables

Analytic engine

Perform any math operation

Punch cardsModern structure: I/O, storage, ALU

Add in 1 second, multiply in 1 minute

Both engines plagued by mechanical problems

George Boole (1847)

Mathematical analysis of logic

Investigation of laws of thought

Herman Hollerith (1889)

Modern day punched card machine Formed Tabulating Machine Company (became IBM)

1880 census took 5 years to tabulate

Tabulation estimates

1890: 7.5 years

1900: 10+ years

Holleriths tabulating machine reduced the 7.5 year estimate to 2 months

Konrad Zuse (1938) Built first working mechanical computer, the Z1

Binary machine

German government decided not to pursue development -- W.W.II already started

Howard Aiken (1943)

Designed the Harvard Mark I

Implementation of Babbages machine

Built by IBM

Mechanical era summary

Mechanical computers were designed to reduce the time required for calculations and

increase accuracy of the results

Two drawbacks

Speed of operation limited by the inertia of moving parts (gears and pulleys)

Cumbersome, unreliable, and expensive

The Electronic Era

Computer Generations

The history of computer development is known as computer generations.

John von Neumann and his Neumann architecture: using a processing unit and a single

separate storage structure to hold both instructions and data.

Each generation of computer is characterized by a major technological development

that fundamentally changed the ways the computers operate.

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This resulted in smaller, cheaper, powerful, efficient and reliable machines.

How many generations of computers we have now?

First Generation

1940s~1956

Vacuum Tubes

Used vacuum tubes for circuitry and magnetic drums for memory

Often enormous, taking up entire rooms

Reliability is a problem

Expensive, used lots of electricity, generated lots of heat Examples: ENIAC-Electronic Numerical Integrator and Calculator,

UNIVAC-UNIVersal Automatic Computer

ENIAC: the first high-speed, purely electronic, Turing-complete, digital computer capable of

being reprogrammed to solve a full range of computing problems .

It contained 17,468 vacuum tubes, 7,200 crystal diodes, 1,500 relays, 70,000 resistors, 10,000

capacitors and 5 million hand-soldered joints. 27 Tons, 8.5ft X 3ft X 80ft.

Second Generation

1956-1963 Transistors

The transistor was far superior to the vacuum tube, allowing computers to become

smaller, faster, cheaper, more energy-efficient and more reliable than their first-

generation predecessors

Still the transistors generated lots of heat

High level programming languages were used like COBOL and FORTRAN

Examples: IBM 1620, CDC 3600

Sample Photo: The IBM 1620 Data Processing System

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Nick name: CADET (Can't Add Doesn't Even Try)

Third Generation

1964-1971

Integrated Circuits (IC). Up to 100 devices per chip.

Transistors were miniaturized and placed on silicon chips, called

semiconductors, which drastically increased the speed and efficiency of computers.

Instead of punched cards and printouts, users interacted with third generationcomputers through keyboards and monitors and interfaced with an operating system

CPL->BCPL->B

Examples: IBM-360, ICL-1900, VAX-750

Sample Photo: VAX - 750

Fourth Generation

1971-present

Microprocessors

Very Large Scale (VLSI), Ultra Large Scale (ULSC), millions of components

could be fit into a single silicon chip

Due to the development of microprocessor it is possible to place computer's

central processing unit (CPU) on single chip

1981: IBM PC, 1984: Apple Macintosh

GUIs, Mouse.

Fifth Generation

Present and Beyond

Based on artificial intelligence, the fifth generation is still in development,

though there are some applications, such as voice recognition, that are being used

today

The use of parallel processing and superconductors is helping to make

artificial intelligence a reality

Quantum computation and molecular and nano technology will radically

change the face of computers in years to come

Any other idea?

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Do you possess any of these devices?????

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lecture 1 introduction to computerarchtecture

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