Uni

vers

ity o

f Pun

e S.

E. I.

T.

Subj

ect c

ode:

214

442

Part

20

: Mem

ory

Org

aniza

tion

Basic

s

Com

pute

r Org

aniz

atio

n

UN

IT

IV

Tush

ar B

. Kut

e,

Dep

artm

ent o

f Inf

orm

atio

n Te

chno

logy

, Sa

ndip

Inst

itute

of T

echn

olog

y &

Res

earc

h Ce

ntre

, Nas

hik.

ht

tp:/

/tus

hark

ute.

com

Mem

ory

Use

d to

stor

e in

form

atio

n w

ithin

a c

ompu

ter ,

eith

er

prog

ram

s or d

ata.

Pr

ogra

ms a

nd d

ata

cann

ot b

e us

ed d

irect

ly fr

om a

disk

or C

D, b

ut m

ust

first

be

mov

ed in

mem

ory

Mai

n M

emor

y &

Cac

he M

emor

y re

fers

as i

nter

nal

mem

ory

beca

use

it is

plac

e at

the

mai

n bo

ard.

Co

mm

unic

ates

dire

ctly

with

CPU

imm

edia

tely.

Se

cond

ary

& te

rtia

ry m

emor

y re

fers

as e

xter

nal

mem

ory

(or a

uxili

ary

mem

ory)

bec

ause

it is

not

lo

cate

d at

the

mai

n bo

ard.

Usu

ally

for b

ack-

up

purp

ose.

Inte

rnal

vs E

xter

nal M

emor

y

Prim

ary

Seco

ndar

y Te

rtia

ry

Fast

Sl

ow

Slow

Dire

ctly

con

nect

ed

to C

PU

Not

dire

ctly

co

nnec

ted

to C

PU

Not

dire

ctly

co

nnec

ted

to C

PU

Expe

nsiv

e Ch

eap

Chea

p Sm

all v

olum

e La

rge

volu

me

Larg

e vo

lum

e

Eg. C

ache

/RAM

Eg

: Disk

Eg

: Tap

e

Mem

ory

Loca

tions

Each

par

t of m

emor

y ha

s a se

para

te

mem

ory

loca

tion,

whi

ch ca

n be

refe

rred

to

usin

g a

mem

ory

addr

ess.

Uni

t Ter

ms

Size

of m

emor

y is

mea

sure

d in

byt

es (o

r mul

tiple

s suc

h as

ki

loby

tes (

KB) o

r meg

abyt

es (M

B)

Num

ber o

f bits

for a

n ad

dres

s to

uniq

uely

acc

ess a

m

emor

y lo

catio

n

Num

ber o

f lo

catio

ns =

2 (n

o of

bits

in th

e ad

dres

s)

Mem

ory

Char

acte

ristic

s

Loca

tion

Capa

city

U

nit o

f tra

nsfe

r Ac

cess

met

hod

Perf

orm

ance

Ph

ysic

al ty

pe

Phys

ical

char

acte

ristic

s O

rgan

isat

ion

Mem

ory

Loca

tion

CPU

In

tern

al

Exte

rnal

M

emor

y Ca

paci

ty

Wor

d siz

e Th

e na

tura

l uni

t of o

rgan

isatio

n Co

mm

on w

ord

size:

8, 1

6, 3

2 bi

ts.

Num

ber o

f wor

ds

or B

ytes

Mem

ory

Uni

t of T

rans

fer

Inte

rnal

Th

e nu

mbe

r of b

its re

ad-o

ut o

f or w

ritte

n in

to m

emor

y at

a ti

me.

U

sual

ly g

over

ned

by d

ata

bus w

idth

Exte

rnal

U

sual

ly a

blo

ck w

hich

is m

uch

larg

er th

an a

wor

d

Addr

essa

ble

unit

Smal

lest

loca

tion

whi

ch c

an b

e un

ique

ly a

ddre

ssed

W

ord

inte

rnal

ly

Mem

ory

Acce

ss M

etho

ds (1

)

Sequ

entia

l St

art a

t the

beg

inni

ng a

nd re

ad th

roug

h in

ord

er

Acce

ss ti

me

depe

nds o

n lo

catio

n of

dat

a an

d pr

evio

us

loca

tion

e.g.

tape

Di

rect

In

divi

dual

blo

cks h

ave

uniq

ue a

ddre

ss

Acce

ss is

by

jum

ping

to v

icin

ity p

lus s

eque

ntia

l sea

rch

Acce

ss ti

me

depe

nds o

n lo

catio

n an

d pr

evio

us lo

catio

n e.

g. d

isk

Acce

ss M

etho

ds (2

)

Rand

om

Indi

vidu

al a

ddre

sses

iden

tify

loca

tions

exa

ctly

Ac

cess

tim

e is

inde

pend

ent o

f loc

atio

n or

pre

viou

s acc

ess

e.g.

RAM

Asso

ciat

ive

Data

is lo

cate

d by

a c

ompa

rison

with

con

tent

s of a

por

tion

of th

e st

ore

Acce

ss ti

me

is in

depe

nden

t of l

ocat

ion

or p

revi

ous a

cces

s e.

g. ca

che

Mem

ory

Perf

orm

ance

Acce

ss ti

me

Tim

e be

twee

n pr

esen

ting

the

addr

ess a

nd g

ettin

g th

e va

lid d

ata

Mem

ory

Cycl

e tim

e

befo

re n

ext a

cces

s Cy

cle

time

is ac

cess

+ re

cove

ry

Tran

sfer

Rat

e Ra

te a

t whi

ch d

ata

can

be m

oved

Mem

ory

Tran

sfer

Rat

e

Tran

sfer

rate

for r

ando

m-a

cces

s m

emor

y =

1/(c

ycle

tim

e)

Tran

sfer

rate

for n

on-r

ando

m-a

cces

s m

emor

y =

T N =

TA +

N/R

W

here

TN =

ave

rage

tim

e to

read

or w

rite

N b

its

T

A = a

vera

ge a

cces

s tim

e

N =

num

ber o

f bits

R =

tran

sfer

rate

, in

bits

per

seco

nd (b

ps)

Mem

ory

Phys

ical

Typ

es

Sem

icon

duct

or

RAM

& R

OM

Mag

netic

Di

sk &

Tap

e

Opt

ical

CD

& D

VD

Oth

ers

Bubb

le

Holo

gram

Phys

ical

Cha

ract

eris

tics

Deca

y

Vola

tility

Er

asab

le

Pow

er c

onsu

mpt

ion

Seria

l vs.

Ran

dom

Acc

ess

Seria

l Acc

ess

Rand

om A

cces

s Se

rially

dat

a is

acc

esse

d Da

ta is

acc

esse

d ra

ndom

ly

Mem

ory

orga

nize

d re

cord

s are

acc

esse

d se

quen

tially

Th

e un

ique

add

ress

of m

emor

y is

acce

ssed

inde

pend

ently

Mem

ory

acce

ss ti

me

depe

nds u

pon

posi

tion

of st

orag

e lo

catio

n M

emor

y ac

cess

tim

e is

inde

pend

ent o

n po

sitio

n of

stor

age

loca

tion

Fast

mem

ory

acce

ss ti

me

Mem

ory

acce

ss ti

me

is le

ss

Chea

per

Com

para

tivel

y co

stly

Non

vol

atile

Vo

latil

e /

non-

vola

tile

e.g.

Mag

netic

Tape

s e.

g. S

emic

ondu

ctor

Mem

orie

s

Mem

ory

Hie

rarc

hy

Mem

ory

syst

ems (

a co

llect

ion

of v

ario

us fo

rms o

f m

emor

y) a

re c

onst

ruct

ed in

a h

iera

rchy

W

hy ?

Ru

le o

f thu

mb:

the

fast

er th

e m

emor

y th

e hi

gher

the

cost

in

term

s of p

rice,

mak

ing

it ve

ry e

xpen

sive

to m

ake

all t

he

mem

ory

out o

f the

fast

est m

emor

y de

vice

s.

Slow

er te

chno

logi

es a

re le

ss e

xpen

sive,

mak

ing

it m

ore

prac

tical

to m

ake

larg

er m

emor

ies o

ut o

f the

se d

evic

es

Goa

l of a

mem

ory

hier

arch

y

to ke

ep th

e da

ta th

at is

acc

esse

d m

ost h

igh

up th

e hi

erar

chy,

so it

can

be a

cces

sed

quic

kly

the

leas

t use

d at

the

bott

om o

f the

hie

rarc

hy.

Mem

ory

hier

arch

y ..

Mem

ory

hier

arch

y ..

Mem

ory

Hie

rarc

hy ..

At

the

top

- reg

ister

s th

ese

are

fast

, bu

t onl

y pr

ovid

e a

very

lim

ited

and

tem

pora

ry st

orag

e us

ually

par

t of t

he p

roce

ssor

in

CPU

Ex

pens

ive

The

next

leve

l - c

ache

mem

ory

exp

ensiv

e fa

st a

cces

s tim

e (ti

me

take

n to

acc

ess t

he d

ata

stor

ed).

The

amou

nt th

at c

an b

e st

ored

(cap

acity

) in

cach

e is

grea

ter t

han

is st

ored

in th

e re

gist

ers,

but

is sl

ower

Th

e ne

xt le

vel -

mai

n m

emor

y/in

tern

al m

emor

y Gr

eate

r cap

acity

than

cach

e, b

ut is

slow

er th

an ca

che

to a

cces

s.

RAM

At

the

botto

m o

f the

hie

rarc

hy

seco

ndar

y st

orag

e/ex

tern

al m

emor

y

the

grea

test

cap

acity

, but

is th

e slo

wes

t to

acce

ss

Back

up/s

tora

ge

Refe

renc

e

Com

pute

r Arc

hite

ctur

e an

d O

rgan

izatio

n

By A

. P. G

odse