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Storing Data On Your Computer. Chapter 12, Exploring the Digital Domain. In this chapter . . . You will learn about. how various storage technologies support processing how data is transferred to and from the processor two classes of secondary memory DASD SASD

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storing data on your computer

Storing Data On Your Computer

Chapter 12,

Exploring the Digital Domain

in this chapter
In this chapter . . .

You will learn about

  • 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
main memory
Main Memory
  • RAM is composed of integrated units
  • SDRAM--Synchronous Dynamic RAM
  • DIMMs--Dual Inline Memory Modules
connecting to the processor
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 processor5
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
types of memory access
Types of Memory Access
  • 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
secondary memory
Secondary Memory
  • SEQUENTIAL ACCESS STORAGE DEVICES AND MEDIA (SASD)
    • magnetic tape
  • DIRECT ACCESS STORAGE DEVICES AND MEDIA (DASD)
    • magnetic floppy disks
    • magnetic hard disks
    • optical discs
direct access storage devices
Direct Access Storage Devices
  • magnetic hard and floppy disks
  • removable hard disks
  • optical discs
    • CD-ROM,
    • CD-R, CD-RW,
    • DVD

GEOMETRY:

TRACKS and SECTORS

dasd media
DASD Media
  • 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
Direct Access
  • 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
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
disk vs file organization
Disk vs. File Organization
  • 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
CD-ROM
  • 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
slide16
CD–R
  • 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 rw
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
slide18
DVD
  • Digital Versatile Disc
  • second generation CD-ROM
  • higher capacity:
    • higher data density
    • multiple sides
    • multiple layers