Computer Organization & Articture No. 3 from APCOMS

8/14/2019 Computer Organization & Articture No. 3 from APCOMS

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COA by Athar Mohsin

Introduction

Lecture 03


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Last week Overview

Computer organization Encompasses all physical aspects of computer systems.

E.g., circuit design, control signals, memory types.

How does a computer work?

Computer architecture

Logical aspects of system implementation as seen by theprogrammer.

E.g., instruction sets, instruction formats, data types, addressingmodes.

How do I design a computer?

At the most basic level, a computer is a device consisting of threepieces:

A processor to interpret and execute programs

A memory to store both data and programs

A mechanism for transferring data to and from the outside world.


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Hertz = clock cycles per second (frequency)

1MHz = 1,000,000Hz Processor speeds are measured in MHz or GHz.

cycle time is the reciprocal of clock frequency.

A bus operating at 133MHz has a cycle time of 7.52 nanoseconds:

Byte = a unit of storage 1KB = 210 = 1024 Bytes 1MB = 220 = 1,048,576 Bytes Main memory (RAM) is measured in MB Disk storage is measured in GB for small systems, TB for large systems.

Millisecond = 1 thousandth of a second

Hard disk drive access times are often 10 to 20 milliseconds. Nanosecond = 1 billionth of a second

Main memory access times are often 50 to 70 nanoseconds.

Micron (micrometer) = 1 millionth of a meter Circuits on computer chips are measured in microns.

Measuring units

133,000,000 cycles/second = 7.52ns/cycle


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An Example System

Computers with large main memory capacity can run larger

programs with greater speed than computers having smallmemories.

RAM is an acronym forrandom access memory. Random access

means that memory contents can be accessed directly if you know its

location.

Cache is a type of temporary memory that can be accessed faster than

RAM.

I/O Ports

Serial ports send data as a series of pulses along one or two data

lines.

Parallel ports send data as a single pulse along at least eight data

lines.

USB, Universal Serial Bus, is an intelligent serial interface that is self-

configuring. (It supports plug and play.)


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Structure & Function

A computer is a complex system contains millions of

electronic components Best is to recognize the hierarchical nature of complex system

A hierarchical system is a set of interrelated subsystem

A hierarchical nature of complex system is essential to design anddescription

Designer will deal to a particular level of the system at any one time At each level the designer is concerned with the STRUCTURE and

FUNCTION

The designer need to deal with a particular level of thesystem at any one time, and concerned with structure and

function at each level Structure is the way in which components relate to each other

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


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Function

The basic functions of allcomputer are:

Data processing

Processor

registers Data storage

Primary and secondary

memories

Data movement Buses I/O

Control

Signalling


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Function

A computer can perform generally four functions Data processing

Few types of data processing

Data storage

Temporary Permanents

On the route to and fro processor

Data movement

Within or to and fro outside

Control

Control of data processing, data storage and data movement

functions

Control manages the computer resources



Function

The computer must be able to process data, that may be in

any forms and range

The computer must also store data

Data storage may be short term or for a longer period

Computer must be able to move data between in and

outside the computer

When data are received from or delivered to a device that is directly

connected to the computer, the process is known as input output

(I/O)

When data is moved over longer distances to or from a remotedevice, the process is known as data communication

There must be control of data processing, data movement

and data storage functions that is done through instructions



Operations



Structure

The computer interacts with its external environment

All the linkages to external environment are classified as peripheral

devices or communication lines

The internal structure of the computer is based on four

structural components:

Central Processing Unit (CPU): controls the operation of the computer and performs the date processing

functions

Main Memory:

Store data

I/O:

Moves data between the computer and its external environment

System Interconnection:

some mechanism that provides for communication among CPU, main

memory and I/O



Structure

The computer interact with its external environment All linkages to the external environment can be classified

as peripheral devices or communication lines

Four main structural components are central processing unit- CPU refers as processor

Controls the operation of the computer and

Performs its data processing functions

Main memory Data storage

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

System interconnection Provides means of communication



Computers consist of many things besides chips.

Before a computer can do anything worthwhile, it must also use

software.

Divide and conquer- a programming technique

Writing complex programs requires a divide and conquer approach,

where each program module solves a smaller problem.

Complex computer systems employ a similar technique through a

series of virtual machine layers

Imagine the machine is to be built from a hierarchy of levels

Each level has a specific function

Each level executes its own particular set of instruction

The Computer Level Hierarchy



Each virtual machine layer

is an abstraction of the

level below it.

The machines at each level

execute their own particular

instructions, calling uponmachines at lower levels to

perform tasks as required.

Computer circuits

ultimately carry out thework.




Level 6: The User Level or upper level

Program execution and user interface level

E.g., Running word processing

The level with which we are most familiar.

Level 5: High-Level Language Level

The level with which we interact when we write programs in

languages such as C, Pascal, Lisp, and Java

These languages must be translated to machine understandable

language Compilers, interpreters

Compiled languages are translated into assembly language and

then to machine language




Level 4: Assembly Language Level

Acts upon assembly language produced from Level 5, as well

as instructions programmed directly at this level

One to one relation- each assembly language instruction is

translated to exactly one machine language instruction

Level 3: System Software Level, deals with operating system

instructions responsible for

Controls executing processes on the system.

Protects system resources.

Instructions translated through Assembly language to machinelanguage instructions often pass through Level 3 without

modification.



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Level 2: Machine Level or ISA level

Also known as the Instruction Set Architecture (ISA) Level.

Consists of instructions that are particular to the architecture of

the machine.

Programs written in machine language need no compilers,interpreters, or assemblers

Programs written in machine language can be executed directly

by the electronic circuits without any interpreter, complier or

translator



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Level 1: Control Level

Control unit make sure that instructions are decoded andexecutes properly

A control unitdecodes and executes instructions and moves datathrough the system

Control unit interprets the machine instructions one at a time

Control units can be microprogrammedorhardwired. A microprogram is a program written in a low-level language that

is implemented by the hardware.

Hardwired control units consist of hardware that directly executesmachine instructions

Through control signals that direct data and instruction traffic toappropriate parts of the system

Hardwired control units are very fast being actual physical parts

Once implemented difficult to modified



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Level 0: Digital Logic Level

This level is where we find digital circuits (the chips).

Digital circuits consist of gates and wires.

These components implement the mathematical logic

of all other levels.


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Computer Organization & Articture No. 3 from APCOMS