A Guide to PC Hardware Maintenance and Repair

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Chapter 11 Working with Removable Disks
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Objectives

• Here is where you get an introduction to the
  basics of magnetic media
• To take a tour of different types of removable
  disks, both past and present
• To get a first hand look at troubleshooting disks
  and file systems

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The Floppy Disk

• The first magnetic storage device used on a PC
• Originally designed as a component for IBMs
  mainframe computers back in 1967

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The Evolution of the Floppy

• The 8 floppy
• Mainframes
• The First IBM PC
• The 5.25 floppy
• Introduced with the XT
• 360K and 1.2MB
• The 3.5 floppy
• Introduced on the AT
• 720K, 1.44MB and 2.88MB

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Storage Data on Magnetic Disks

• Data stored in 512K sectors
• A ring of sectors that travels the entire
  circumference of the disk is a track
• Two factors that determine disk capacity are
  sectors per track and tracks per inch
• Sectors are mapped out and information about them
  is stored in the File Allocation Tables (FAT)

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Floppy Disk Formats over Time
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Floppy Disk Formats over Time
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Floppy Diskette Cables

• 34-conductor
• Can support up to two devices
• Device on end opposite of twist is bootable device

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Cable-specific issues

• 34th conductor is the drive change indicator
• You run a directory of a disk and look at the
  contents
• Run another disk and the contents are the same
• 34th conductor is crimped or broken

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Cable-specific issues, Part II

• The floppy disk drive isnt recognized and the
  activity light never goes off
• The cable is plugged in backwards, either on the
  motherboard or on the drive
• The drive isnt recognized and no lights show
• Cable isnt plugged in
• System BIOS is set to No Floppy

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Diskette Problems

• Data Read Errors
• Seek error writing Drive A
• Sector not found reading Drive A
• Abort, Retry, Fail?
• Abort, Retry, Fail, Ignore?
• Data error reading Drive A

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Diskette Drive Problems

• Drive Not Ready
• Can indicate either an unreadable diskette or a
  bad drive
• FDD Controller Failure
• Usually means a bad disk drive
• Could also indicate a motherboard controller
  failure

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Other Removable Disks

• ZIP and JAZZ drives
• The Super Floppy
• HiFD

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Tape Drives

• Quarter Inch Cartridge (QIC)
• Digital Audio Tape (DAT)
• Digital Linear Tape (DLT)
• Advanced Intelligent Tape (AIT)
• Scalable Linear Recording (SLR)