gate computer organization & architecture book

8/10/2019 GATE Computer Organization & Architecture Book

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COMPUTER ORGANIZATION

ARCHITECTURE

For

Computer Science

Information Technology

By

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Syllabus Computer Organization

THE GATE ACADEMY PVT.LTD. H.O.: #74, Keshava Krupa (third Floor), 30thCross, 10thMain, Jayanagar 4thBlock, Bangalore-11 080 65700750 i f @th t d C i ht d W b th t d

Syllabus for

Computer Organization and Architecture

Machine instructions and addressing modes, ALU and data-path, CPU control design, Memory

interface, I/O interface (Interrupt and DMA mode), Instruction pipelining, Cache and main

memory, Secondary storage.

Analysis of GATE Papers

(Computer Organization and Architecture)

Year

Percentage of marks

Overall Percentage

2013

11.00

9.48

2012

6.00

2011

7.00

2010

9.00

2009

6.66

2008

16.00

2007 9.33

2006

9.33

2005 14.67

2004

10.00

2003

5.33


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Contents Computer Organization

THE GATE ACADEMY PVT.LTD. H.O.: #74, Keshava Krupa (third Floor), 30thCross, 10thMain, Jayanagar 4thBlock, Bangalore-11

080 65700750 i f @th t d C i ht d W b th t d Page I

C O N T E N T S

Chapter Page No.

1. Introduction 1 28

Computer Design 1 4

Binary Data Representation 4 12

CPU Design 12 13

Binary Adder 13 19

Arithmetic Logic Unit 19 22

Assignment 1 23

Assignment 2 24

26 Answer Keys 27

Explanations 27 28

2. Memory 29 60

Memory Parameter 29 30

Main Memory 31 36

Cache Memory 36 42

Virtual Memory 42 45

Solved Examples 45

47 Assignment 1 48 51

Assignment 2 51 53

Answer Keys 54

Explanations 54 60

#3. Pipelining and Vector Processing 61 82

Parallel Processing 61 65

Pipelining 65 74

Solved Example 74

Assignment 1 75 77

Assignment 2 77 78

Answer Keys 79

Explanations 79 82

4. Instruction Set and Addressing Mode 83 99

Introduction 83

Instruction format 83 86

Addressing Modes 86 -87


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080 65700750 i f @th t d C i ht d W b th t d Page II

CISC and RISC 87 88

Solved Example 89

Assignment 1 90

93

Assignment 2 93 94

Answer Keys 95

Explanations 95 99

#5. CPU Operation and Design 100 - 110

CPU Operations 100 103

Data Path and Control Path 103 104

Machine Cycle 104 107

Assignment 108 109

Answer Keys 110

Explanations 110

#6. I/O Interface (Interrupt and DMA Mode) 111 131

Introduction 111

Difference between the Computer and Peripheral Devices 111

I/O Bus and Interface Modules 111 112

Modes of Data Transfer 112

116 I/O Communication Technique 116 118

Direct Momory Access (DMA) 119 124

Assignment 1 125 126

Assignment 2 126 128

Answer Keys 129

Explanations 129 131

#7. Control Unit Design 132 141

Von-Neumann Architecture 132

133 Von-Neumann Bottleneck 133

Harvard Architecture 134

Control Unit 134 137

Solved Examples 137 138

Assignment 139 140

Answer Keys 141

Explanations 141


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080 65700750 i f @th t d C i ht d W b th t d Page III

Module Test 142 153

Test Questions 142 148

Answer Keys 149

Explanations 149 153

Reference Books 154


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Chapter-1 Computer Organization

THE GATE ACADEMY PVT.LTD. H.O.: #74, Keshava Krupa (third Floor), 30th

Cross, 10th

Main, Jayanagar 4th

Block, Bangalore-11

080 65700750 i f @th t d C i ht d W b th t d P 1

CHAPTER 1

Introduction

Computer Architecture

Computer architecture deals with the structure and behavior of the computer system. It includesthe information formats, the instruction set and the hardware units that implement the

instructions along with the techniques for addressing memory.

Computer Organization

Computer organization deals with the way the various hardware components operate and the

way they are connected together to form the computer system. It also deals with the units of the

computer that receive information from external sources and send computed results to externaldestinations.

Computer Design

Computer design is concerned with the hardware design of the computer. This aspect of

computer hardware is sometimes referred to as computer implementation. Figure 1.1 shows the

basic building blocks of a typical computer system.

The basic blocks available in any digital computer are, Arithmetic Logic Unit (ALU), ControlUnit, Memory and Input/Output Unit.

Input Unit

It is a medium of communication between the user and the computer. With the help of input

unit only, it is possible to enter programs and data to the computer.

Examples

Keyboard, floppy disk drive, hard disk drive, mouse, Magnetic Ink Character Recognition(MICR), Optical Character Recognition (OCR), paper tape reader, Magnetic tape reader,

Scanner etc.

Output Unit

It is a medium of communication between the computer and the user. With the help ofoutput unit only, it is possible to get results from the computer.

Example: Printers, Video Display Unit (VDU), Floppy disk drive, Hard disk drive, Magnetictape drive, punched cards, paper tape, plotter, digitizer etc.

MEMORY

INPUT OUTPUT

ALU

CPU

CU

Fig. 1.1 Basic functional units of a computer


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Memory

The memory unit is responsible for storing the user programs and data. The digital computer

memory unit mainly consists of two types of memories: Read Only Memory (ROM) and ReadWrite Memory (R/WM) or Random Access Memory (RAM).

ROM

ROM is used to store permanent programs or system programs. It does not have writecapability.

Types: PROM, EPROM, EEPROM

RAMIt is also called user memory because the user programs or application programs are

stored in this memory. The CPU is able to write or read information into or from thistype of memory.

Types:static, dynamic, scratch pad etc.

Central Processing Unit CPU)

The ALU and Control Unit together are called CPU. It is the heart of any digital computer.

ALU Arithmetic Logic Unit)

The data processing part of CPU is responsible for executing arithmetic and logical instructionson various operand types including fixed point and floating point numbers.

Various circuits used to execute data processing instructions are usually combined in a single

circuit called an arithmetic logic unit (ALU). The complexity of an ALU is determined by the wayin which its arithmetic instructions are realized. Simple ALUs that perform fixed point additionand subtraction as well as word based logical operations, can be realized by combinationalcircuits. Much more extensive data processing and control logic necessary to implement is

floating point arithmetic in hardware.

Example

For finding the sum of a series , how will you usean ALU without a multiplier unit but with an adder and barrel shifter? Barrel shifter is a shifter

that does shift at an instance.SolutionLeft shift by 7 means multiplication by 128,6 means multiplication by 64,5 means multiplicationby 3 and means multiplication by. Hence the shift operations will be faster forcomputing . Using the barrel shifter seven times for shifting by 3 .. we find and store leftshifted values of in a register and add these.Two Types of ALUs

1.

Combinational ALUs

The simple ALU combine the functions of s complement adder-subtracter with those of acircuit that generates word based logic functions of the form f(x, y).For example AND XOR and NOT. They can thus implement most of a CPUs fixed point dataprocessing instructions.

2.

Sequential LUs

Both multiplication and division can be implemented by combinational logic. It is generally

impractical to merge these operations with addition and subtraction into a single,

combinational ALU.


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The combinational multipliers and dividers are costly in terms of hardware. They are also

much slower than addition and subtraction.

An n-bit combinational multiplier or divider is typically composed of n or more levels of

add-subtract logic making multiplication and division at least n times slower thanaddition (or) subtraction, where addition and subtraction each take one clock cycle, whilemultiplication and division are multicycle operations.

Example

How many 16-bit ALU slices can be used for designing a 64-bit ALU?

SolutionFour slices will be needed in parallel if ALU 64-bits operations are to take nearly the same time

as 16-bit slice, and four slices will be needed in series if ALU 64- bits operations are to takenearly four times of 16-bit slice.

Interconnection of basic of blocks

In order to form an operational system individual components or parts of computer that we

have discussed need to be connected in some organized way for this purpose u is introducedwhich is defined as a group of lines that serves as a connecting path for several devices. Theselines carry data, address and control signals.

Figure 1.2 shows a exemplanary interconnection using single bus structure

Since, this bus can be used only for single transfer at a time Multiple busesare introduced so asto achieve more concurrency in operations so that two or more transfers can be carried out atthe same time. Hereby, increasing performance but at an increased cost.

Control Unit

The control unit (CU) is the heart of the CPU. Every instruction CPU supports has to be decidedby the CU and executed appropriately. Every instruction consists of a sequence of micro

instructions that carries out that instruction the CU controls the elements inside the CPU theinterface to the external data rate.

Following are the basic tasks of the control unit

1. For each instruction the CU causes the CPU to go through a sequence of control steps:

2.

In each control step the CU issues a set of signal which caused the correspondingoperation to be executed.

OutputMemory CPU

Fig1.2. Single-bus Structure

Input


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3. The signals to be generated by CU depends upon the actual step to be executed, the

condition and states of flag register of the processor, the actual instruction to be executed

and any external signals received on the system bus (i.e., interrupt signals)

Binary data representation

In digital computer, integers are represented as binary numbers of fixed length. A binarynumber of length x is an ordered sequencex x x . . . x xOf binary digits where each digit

x(also known as a bit)

Can assume one of the values 0 or 1The above sequence of x digits represents the integer value

X x x . . . . x x x.

Since operands and results in an arithmetic unit are started in resisters of a fixed length, there isa finite number of distances that can be represented with in an arithmetic unit. Let x andxdenote the smallest and largest representable value. We say that x x is the rangeof the number

A sequence of n digits in a register does not necessarily have to represent an integer. We can getsuch a sequence to represent a mixed number that has a fractional part as well as an integral

part. This is done by portioning the n digits into two series; k digits in integral part and in digitsin the fractional part, satisfying k +m = n

xx. . . . . xx xx. . . . . x The above sequence of n digits represents the value

X x x . . . . . x x x . . . . . x x

The radix point is now stored in the register but is understood to be in a fixed position between

k most significant digits and the m least significant digits. For this reason we call suchrepresentation as fixed-pointrepresentation

IR

Common signals

internal to the CPU

Common signals

internal on system bus

Signals from system bus

Control Unit (CU)

Clock

Flags


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Representation of negative numbers

For fixed point numbers, we have to determine the way negative numbers are represented. Two

different terms are commonly used:

1.

Sign and magnitude representation

Which is also called the signed-magnitude method

2. Complement representationWhich comprises two alternatives

Signed magnitude

In this representation the first digit is the sign digit and the remaining digits representmagnitude. In binary case sign bit is normally selected to be o for +ve numbers and 1 for +veones.

Let the

digits representing the magnitude be partitioned into

and m digits in the

integral and fractional part, respectively. The largest representable number is then, ( )Thus the range of +ve numbers is [ ]and the range of ve number is ( ).We therefore have two representations of zero, one +ve and ve.A major disadvantage of the signed-magnitude representation is that the operation to beperformed may depend on the signed of the operands. This is avoided in the complementrepresentation methods

Complement representationThere are two alternatives

1. Radio complement also called s complement2. Diminished radix complement also called s complement

In both complement method, a +ve number is represented in the same way as in the signal

magnitude method, where a negative number is represented by , where R is aconstant. Such a representation satisfies the basis identify One of the major advantages of a complement method is that no decisions have to be made

before executing an addition or substation If

the

ve result

is already in the same complement form. However if

, the

correct result should be , while . The addition term R must bediscarded, and the value of R should be selected to simplify or completely eliminate thiscorrection step.

In case of s complement the value of R is and for complement the value of R is .The range of numbers in the twos complement for is This range is slightly a symmetric as then is one more ve number than are +ve numbers, on thehand these is a unique representation for 0.

The range of representable number in the ones complement system is symmetric


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gate computer organization & architecture book

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