Storing Data On Your Computer

Chapter 12,Exploring the Digital Domain

In this chapter . . .

how various storage technologies support processing

how data is transferred to and from the processor

two classes of secondary memory DASD SASD

How data is organized on magnetic and optical media

You will learn about

RAM is composed of integrated units

SDRAM--Synchronous Dynamic RAM

DIMMs--Dual Inline Memory Modules

Main Memory

Connecting to the Processor

a bus is a connection between components

classifying buses data width speed

early designs featured a single system bus

Connecting to the Processor

Modern designs feature two-tier chipset

“northbridge”--controller connecting CPU with memory, graphics controller

“southbridge”--controller connecting I/O and other devices

Memory Hierarchy I

Memory Hierarchy II

RANDOM ACCESS items are independently addressed access time is constant

DIRECT ACCESS items are independently addressed in regions access time is variable—though not

significantly SEQUENTIAL ACCESS

items are organized in sequence (linearly) access time is significantly variable

Types of Memory Access

SEQUENTIAL ACCESS STORAGE DEVICES AND MEDIA (SASD) magnetic tape

DIRECT ACCESS STORAGE DEVICES AND MEDIA (DASD) magnetic floppy disks magnetic hard disks optical discs

Secondary Memory

magnetic hard and floppy disks removable hard disks optical discs

CD-ROM, CD-R, CD-RW, DVD

GEOMETRY: TRACKS and SECTORSGEOMETRY: TRACKS and SECTORS

Direct Access Storage Devices

CAV — constant angular velocity (e.g., floppy and hard disks)

CLV — constant linear velocity (e.g., optical discs)

Zoned CAV — number of sectors depends upon zone

DASD Media

SEEK — controller advances read/write head to proper track

LATENCY — waits for proper sector to rotate under head

READ/WRITE — disk head scans the sector for read or write

Direct Access

FLOPPY DISKS 5.25 and 3.5 inch

diskettes CAV 1.44 – 2.88 MBytes

capacity access: drive speeds –

600 r.p.m. inexpensive, archival

uses for small amounts of data

offline storage

HARD DISKS 3.5 inch has approx

10-30K tracks per side

ZCAV multiple disk, sides

(cylinders) high capacity access: drive speeds –

5,400; 7,200 r.p.m. and higher

on-line storage

Magnetic Disks

data is stored in blocks blocks occupy sectors sectors on tracks files have names files are indefinite in size files may be updated (in

part or whole) directory entries record

file data file allocation table

keeps track of file pieces

Disk vs. File Organization

based on CDDA technology

CLV geometry density: 16,000 tpi up to 650 MBytes nonerasable,

nonwriteable storage discs are mastered,

pressed (mass production)

multispeeds drives common

CD-ROM

discs are “burnt” one at a time

high intensity laser beam used for recording pregrooved tracks

low intensity beam for reading

attributes similar to CD-ROM

CD–R

CD-RW CD-ReWritable--

writable, erasable disc

optical phase-change recording

Erased, written up to 1,000 times

UDF (Universal Disk Format) variable-length

packets fixed-length packets

DVD

Digital Versatile Disc second generation CD-

ROM higher capacity:

higher data density multiple sides multiple layers