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Secondary Memory and Input/Output

Secondary Memory and Input/Output. Exploring the Digital Domain. I/O Subsystem. Input/Output exchanging data and instructions between the user and the computer Secondary Storage auxiliary storage for data and instructions. Secondary Memory (Storage).

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Secondary Memory and Input/Output

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  1. Secondary Memory and Input/Output Exploring the Digital Domain

  2. I/O Subsystem • Input/Output • exchanging data and instructions between the user and the computer • Secondary Storage • auxiliary storage for data and instructions

  3. Secondary Memory (Storage) • backup or alternative storage in place of (volatile) RAM • cheaper, mass storage for long term use • secondary memory devices (and media) are distinguished by their capacities, speed, and cost

  4. 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

  5. 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

  6. Memory Hierarchy I

  7. Memory Hierarchy II

  8. Magnetic Tape • stores data represented by magnetized particles in linear tracks • magnetized clusters or domains are aligned to represent binary codes

  9. Magnetic Tape

  10. Magnetic Tape Formats • LONGITUDINAL • older format used for record-keeping • SERPENTINE • used for system backups • HELICAL SCAN • high capacity formulation used for system backups and archives

  11. Longitudinal (9-track)

  12. Serpentine (QIC)

  13. Direct Access Storage Devices • magnetic hard and floppy disks • removable hard disks • optical discs • CD-ROM, CD-R, • WORM, • magneto-optical GEOMETRY: TRACKS and SECTORS

  14. 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

  15. 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

  16. FLOPPY DISKS 5.25 and 3.5 inch diskettes 1.44 – 2.88 MBytes capacity access: drive speeds – 600 r.p.m. inexpensive, archival uses for small amounts of data HARD DISKS 3.5 inch has approx 3,000 tracks per side multiple disk, sides (cylinders) high capacity access: drive speeds – 3,600 up to 7,200 r.p.m. on-line storage Magnetic Disks

  17. 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)

  18. Optical Discs • Compact Disc–Read Only Memory (CD-ROM) • archived and published information • high capacity • Compact Disc–Recordable (CD-R) • recordable • readable using CD-ROM technology • Write Once, Read Many (WORM) • high capacity archival storage • Magneto-Optical Discs • erasable, high capacity, on-line storage alternative • Digital Versatile Discs (DVD) • Very high capacity, read-only storages

  19. 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

  20. 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

  21. Other Optical Media • Magneto-Optical • combines magnetic and optical technologies • erasable, readable-writable storage • very high capacity • not yet economical • Digital Versatile Disc (DVD) • successor to CD-ROM technology • very high capacity read-only storage • multiple disc, multiple sided storage

  22. Input Peripherals • keyboard • mouse • scanners (flatbed, slide, and drum) • digital cameras • sound digitizers • MIDI (Musical Instrument Digital Interface) • Video digitizers

  23. Output Peripherals • video display monitors • monochrome and color • CRT and LCD

  24. CRT technology • cathode ray tube (CRT) • phosphors excited by electron gun beams • RGB composite color • horizontal scanning pattern to refresh phosphors

  25. Output Peripherals • video display monitors • monochrome and color • CRT and LCD • printers • character, line, and page

  26. CHARACTER dot matrix low-cost, text and graphic printers slow-speed, low quality inkjet medium-priced general-purpose PAGE laser printers high-quality assortment of sizes, performance, and cost Printers

  27. Output Peripherals • video display monitors • monochrome and color • CRT and LCD • printers • character, line, and page • sound and voice output • MIDI synthesizers

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