ITEC255 Chapter 1

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ITEC255-ComputerOrganization&Architecture

Eastern Mediterranean University

School of Computing and Technology

ITEC255

Computer Organization

& Architecture

INTRODUCTION

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Introduction

The course is about the structureand functionof computers.

The purpose is to present the nature and characteristics of

modern-day computers.

The intent of this course is to provide:

a detailed discussion of the fundamentals of computer

organization and architecture to relate these to contemporary computer design issues.


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Organization and Architecture

Computer architecturerefers to those attributes of a systemvisible to a programmer or those attributes that have a direct

impact on the logical execution of a program.

Examples of architectural attributes include:

Instruction set

Number of bits used to represent various data types (e.g.

numbers, characters)

I/O mechanisms

Memory addressing techniques


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Computer organizationrefers to the operational units and

their interconnections that realize the architectural

specifications.

Examples of organizational attributes are transparent to

programmer, such as:

Control signals

Interfaces between the computer and peripherals Memory technology being used



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As an example:

The fact that a multiply instruction is available is a

computer architecture issue.

How that multiply is implemented is a computer

organizationissue.



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Many computer manufacturers offer a family of computer

models all with thesame architecture.

All Intel x86 family share the same basic architecture.

The IBM System/370 family share the same basic architecture.

This gives compatibilityfor new models.

Organization differsbetween different versions with changing

technology.



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Structure and Function

Modern computers contain millions of electronic

components.

The key to describe such systems is to recognize their

hierarchical nature.

A hierarchical system is a set of layers or levels of

interrelated subsystems.


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The designer need only deal with a particular level of the

system at a time.

At each level, the system consists of a set of components and

their interrelationships.

The behavior at each level depends only on a simplified,

abstracted characterization of the system at the next lower

level.



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At each level, the designer is concerned with:

Structure: The way in which components relate to each

other (interrelated).

Function: The operation of each individual components as

part of the structure.

We will usually describe systems from the top-down, instead

of bottom-up.



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Function

There are only four basic functions that a computer can

perform.1. Data processing: The data may take a wide variety of form,

but only a few fundamental methods or types of data

processing.

2. Data storage: There are long-term or short, temporary storage.

3. Data movement

Input/Output: When data are received from or delivered to

a peripheral, a device connected directly to the computer. Data communication: When data is moved over longer

distances, to or from a remote device.

4. Control:Control of the above functions, by instructions

provided by the user of the computer (i.e. their programs).


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Function


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Within the computer, a control unit manages the computers

resources and orchestrates the performance of its functional

parts in response to those instructions.

Function


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The number of possible operations that can be performed is

four:1. The computer can function as a data movement device,

simply transferring data from one peripheral or

communications line to another.

Function


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2. The computer can function as a data storage device, with

data transferred from external environment to computer

storage (read) and vice versa (write).

Function


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3. The computer can operatedata processing in storage.

Function


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4. The computer can operatedata processing between storage

and external environment.

Function


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Structure

Figure shows thesimplest possible representation of a

computer.

The computer interacts in some fashion with its external

environment.

In general, all of its linkages to the external environment can

be classified as peripheral devices or communication lines.


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There are four main structural components in the internal

structure of the computer:

1. Central processing unit (CPU): Controls the operation

of the computer and performs its data processing

functions. Often simply referred to as processor.

2. Main memory: Stores data.

3. I/O: Moves data between the computer and its external

environment.

4. System interconnection: Some mechanism that provides

communication among CPU, main memory and I/O. A

common example of system interconnection is by means

of asystem bus, consisting of a number of conducting

wires to which all the other components attach.

Structure


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Structure

Internal structure of a computer:

Computer

Main

Memory

I/O

Systems

Bus

Peripherals

Communicationlines

CPU

Computer


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Structure

CPU

Traditionally, there has been just a single processor. In recent

years, there has been increasing use of multiple processors in a

single computer.

Major structural components of CPUare as follows:

Control Unit:Controls the operation of CPU and hence

computer.

Arithmetic and logic unit (ALU):Performs computers

data processing functions.

Registers:Provides storage internal to CPU.

CPU interconnection:Some mechanism that provides

communication among control unit, ALU and registers.


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Internal structure of a CPU:

ALU

Control

Unit

Internal Bus

Registers

CPU

MainMemory

I/O

Systems

Bus

CPU

Structure CPU

Computer


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There are several approaches to the implementation of the

control unit.

The most common is a microprogrammedimplementation.

A microprogrammed control unit operates by executing

microinstructionsthat define the functionality of the control

unit.

Structure

Control Unit


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Control

Memory

Control Unit

Registers

and

Decoders

Sequencing

Logic

Control Unit

ALU

Control

Unit

InternalBus

Registers

CPU

Internal structure of a control unit:

Structure Control Unit


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Why Study Computer Organization and Architecture?

To be a professional in any field of computing today, one

should not regard the computer just as a black box that

executes programs by magic.

Students need to understand computer architecture in order

to structure a program so that it runs more efficiently on a

real machine.

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ITEC255 Chapter 1