Transcript Storing data on your computer

Storing Data On Your Computer
Chapter 12,
Exploring the Digital Domain
In this chapter . . .
You will learn about
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how various storage technologies support
processing
how data is transferred to and from the
processor
two classes of secondary memory
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DASD
SASD
How data is organized on magnetic and
optical media
Main Memory
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RAM is composed of
integrated units
SDRAM-Synchronous
Dynamic RAM
DIMMs--Dual Inline
Memory Modules
Connecting to the Processor
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a bus is a
connection between
components
classifying buses
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data width
speed
early designs
featured a single
system bus
Connecting to the Processor
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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
Types of Memory Access
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RANDOM ACCESS
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DIRECT ACCESS
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items are independently addressed
access time is constant
items are independently addressed in regions
access time is variable—though not significantly
SEQUENTIAL ACCESS
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items are organized in sequence (linearly)
access time is significantly variable
Secondary Memory
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SEQUENTIAL ACCESS STORAGE
DEVICES AND MEDIA (SASD)
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magnetic tape
DIRECT ACCESS STORAGE DEVICES
AND MEDIA (DASD)
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magnetic floppy disks
magnetic hard disks
optical discs
Direct Access Storage Devices
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magnetic hard and floppy disks
removable hard disks
optical discs
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CD-ROM,
CD-R, CD-RW,
DVD
GEOMETRY:
TRACKS and SECTORS
DASD Media
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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
Direct Access
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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
Magnetic Disks
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FLOPPY DISKS
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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
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HARD DISKS
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3.5 inch has approx 1030K 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
Disk vs. File Organization
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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
CD-ROM
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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–R
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discs are “burnt” one at
a time
high intensity laser
beam used for
recording pregrooved
tracks
low intensity beam for
reading
attributes similar to CDROM
CD-RW
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CD-ReWritable-writable, erasable disc
optical phase-change
recording
Erased, written up to
1,000 times
UDF (Universal Disk
Format)
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variable-length packets
fixed-length packets
DVD
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Digital Versatile Disc
second generation CD-ROM
higher capacity:
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higher data density
multiple sides
multiple layers