Floppy Drives

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Chapter 7

• Floppy Drives

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You Will Learn

• How floppy drives work
• How to exchange and support floppy drives

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How Floppy Drives Work

• How data is physically stored on a floppy disk
• How the OS logically views that data

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Floppy Drive Subsystem

• Many people have called the floppy dead. There
  are some applications where a floppy can be very
  useful. For example, when installing Windows XP,
  you press F6 to install SATA drivers from floppy.
• A floppy fits in a 3.5 external bay connected
  to the motherboard through a 34 pin ribbon
  cable. The twist goes towards the floppy.
• Systems support two floppy drives with reserved
  letters A and B
• Floppy drives use Berg connectors for power.

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How Data Is Physically Stored on a Floppy Disk

• Floppy drives hold 720 kB, 1.44 MB, or 2.88 MB of
  data. The most common is 1.44 MB.
• 720 KB - Double density
• 1.44 MB High density
• 2.88 MB Extra-high density
• In concentric circles (tracks or cylinders)
• Each track is divided into sectors
• Each sector holds 512 bytes of data

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How Data Is Physically Stored on a Floppy Disk
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How Floppy Disks Vary

• Organization of tracks and sectors
• Density at which data can be stored
• Intensity of magnetic spots on magnetized plastic
  surface of the disk

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Inside a Floppy Disk Drive
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How Data Is Physically Stored on a Floppy Disk
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How Data Is Logically Stored on a Floppy Disk

• Cluster
• Smallest logical unit of space allocated to a
  file
• On a 3½-inch high-density floppy disk, one
  cluster one sector (512 bytes)

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How Data Is Logically Stored on a Floppy Disk
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Ways to Format a Floppy Disk

• Format command from a command prompt
• Windows Explorer, right-click the 3½ Floppy (A)
  icon and select Format on shortcut menu

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Formatting Process for a Floppy

• Creates tracks and sectors
• Creates boot record
• Creates two copies of file allocation table (FAT)
• Creates root directory

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Boot Record

• First sector of the disk - The boot record is
  always located at the beginning of the disk at
  track 0, sector 1.
• Stores basic information about how the disk is
  organized
• Has a bootstrap loader that can be used to boot
  from the disk.
• IO.SYS or NTLDR make it bootable
• To make a floppy bootable, you have to copy the
  boot files with format a /s, sys a, or select
  the Create an MS-DOS startup disk check box in
  Windows Explorer.

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File Allocation Table (FAT)

• Lists location of file segments (clusters) on a
  disk in a one-column table
• Width of each entry in the column is 12 bits
  that is why it is called FAT12
• Lists how each cluster on the disk is currently
  used

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Root Directory Table

• Lists all files and subdirectories assigned to
  this table
• Contains a fixed number of rows to accommodate a
  predetermined number of files and subdirectories

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Important Items in the Root Directory

• Filename and extension this includes both 8.3
  and LFN format names
• Time and date of creation or last update
• File attributes R, A, S, H

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Exchanging and Supporting Floppy Drives

• How to replace the drive
• How to add an additional floppy drive to a
  computer system
• Problems that can occur with a floppy drive and
  its support system

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Replacing a Floppy Drive

• Check that computer and other peripherals are
  working
• Turn off computer and remove cover
• Unplug data cable and power cable from old drive
  unscrew and dismount the drive
• Slide new drive into the bay reconnect data
  cable and power cable
• Turn on computer check setup test the drive
  turn off computer and replace the cover

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Removing the Power Cable
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The Data Cable

• This is a 34-pin data cable for floppy drives.
• The larger connectors were designed to connect to
  very old 5 ¼ floppy drives.
• The drive at the twisted end will be drive A.
  The drive in the middle, before the twist, is
  drive B The twist in the cable replaces drive
  configuration jumpers.

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Reconnecting the Data Cable

• Floppy drives lack the consistency of hard
  drives with the red stripe for pin 1. The red
  stripe is still for pin 1, but it may be on the
  right or the left.
• To make sure you turn the cable correctly, look
  for a pin 1 designation and turn the red stripe
  towards it. You can also hope the connector is
  keyed most of them are not.
• If you turn the computer on and the floppy drive
  access light stays on, you have the data cable
  backwards on either the motherboard or the drive.

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Requirementsfor Adding a New Drive

• Empty external 3.5 bay
• Extra power cable (or Y splitter)
• Extra connection on floppy drive data cable.
  Some floppy cables dont have two connectors, so
  you may need to replace the data cable.

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Adding a New Drive

• Slide the drive into the bay screw it down
• Connect the cable and power cable
• Change setup in BIOS

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When a Floppy Disk Doesnt Work

• Check simple things first
• Check physical condition of the floppy diskette
• Check error messages
• Error messages in 600 range occur when a floppy
  drive does not pass POST test
• Check CMOS settings is the drive enabled in
  BIOS
• Check data and power cables connected to the drive

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Potential Problems

• Application points to a different drive If an
  application is trying to save a file on another
  drive, it wont magically show up on the floppy.
• Unrelated error locked up the system not all
  errors that occur after installing a floppy drive
  are related to the floppy drive.
• System BIOS or CMOS setup is not correctly
  configured
• Disk in drive is not formatted change to a
  known good floppy diskette
• Floppy drive or floppy diskette may be bad

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Potential Problems

• Shuttle window on floppy disk cannot open fully
  try another floppy
• Cable on motherboard to the drive is damaged or
  poorly connected. Also look to see if someone
  else damaged the pins.
• Edge color, typically red, on cable is not
  aligned with pin 1. Look for the pin 1
  indicator, a 1, a 2 or a ?. Also, understand
  that if a pin is labeled 33 or 34, place the red
  side of the data cable on the other end.
• Power supply or power lead from supply is bad.
  Test with a power supply tester.

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Potential Problems

• Power supply cable to the drive is loose or
  disconnected. Also, check to see if a power
  connector pin is bent.
• Command just issued has a mistake or is the wrong
  command
• Disk is not inserted correctly. Is it all the
  way in until it clicks this is how you can tell
  it is seated.

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Common Error Messages

• Non-system disk or disk error. Replace and strike
  any key when ready. No operating system was
  found on the floppy. This is often because
  someone accidentally left a floppy in the drive,
  and it is listed before the HDD in the boot order
  in the BIOS.
• Bad or missing COMMAND.COM - An error such as
  "Bad or missing COMMAND.COM" means that the two
  hidden files are present but Command.com is not
  present or is corrupt. (Win9x)
• Error in Config.sys line xx this usually
  indicates you had a syntax error when you edited
  the config.sys file, which loads real-mode
  drivers.
• Himem.sys not loaded this means the himem.sys
  was not loaded , so extended memory will be
  unavailable (Win9x)
• Missing or corrupt Himem.sys this means the
  himem.sys was not loaded because it was missing
  or had been damaged, so extended memory will be
  unavailable (Win9x)

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Common Error Messages

• Invalid Drive Specification The drive that you
  specified was not detected by the BIOS. Reboot
  and check the BIOS configuration.
• Not ready reading drive A, Abort, Retry, Fail?
  The floppy diskette was not readable. Reseat it.
  If it still doesnt work, replace it.
• General failure reading drive A, Abort, Retry,
  Fail? This is much like the last error message
  but worse. Reseat the diskette, replace the
  diskette, or replace the drive.
• Track 0 bad, disk not usable This means your
  floppy is bad throw it away. Track 0 is bad.
  It is also possible that the drive is bad. Try
  another diskette.
• Write-protect error writing drive A - Someone
  moved the write protect tab or covered the hole
  with tape.

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Summary

• Main uses of floppy drives
• Troubleshooting a failed boot
• Quick and easy way to transfer small files from
  one PC to another
• How data is physically and logically stored on a
  floppy disk
• Sector (physical storage)
• Cluster (logical storage)
• How to install a floppy drive on a PC