A Guide to PC Hardware Maintenance and Repair

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Chapter 13 Hard Disk Interfacing and Disk
Management
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• In this chapter youll get an overview of some
  different interfaces used by disk drivers over
  the years
• Youll learn basic disk preparation
• Most importantly, you will learn some
  preventative maintenance techniques to keep you
  drives running smoothly

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In the Beginning

• The first hard disks for the PC were the ST-506
  and the ST-412
• MFM drives
• The ST-506 was a whopping 5MB. FIVE WHOLE
  MEGABYTES!!!
• IBM demanded something bigger.
• So the 10MB ST-412 was born
• MFM Drives required a data cable and a control
  cable

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ESDI

• Enhanced Small Device Interface
• Similar to MFM in technology
• Some of the controller circuitry moved over onto
  the drive
• Like MFM, required a specialized controller card
  and two cables

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IDE

• Integrated Drive Electronics
• All controller circuitry moved onto device

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ATA

• Advanced Technology Attachment (First generation
  IDE)
• supported only 1 port
• 2 devices
• only hard drives
• due to an addressing issue, the largest drive
  supported was 504MB
• Used Programmed Input/Output (PIO)
• CPU had to negotiate the transfer of each packet
  of data

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ATA-2 and 3

• Eliminated addressing error
• now supports drives up to 8GB
• Introduced Multi-word DMA
• Once the CPU negotiated the transfer of data from
  the drive to memory, it stepped aside and let the
  data flow
• Introduced Logical Block Addressing (LBA)
• An Int13h extension that allows hard drives up to
  137GB

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What is EIDE?

• It was never an industry standard
• Western Digital incorporated some features that
  would eventually become a part of ATA-2
• Not all of WDs features would be accepted as an
  industry standard
• Still, the term took hold

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ATA-4

• Introduced a more efficient command set
• Incorporated cyclical redundancy checking (CRC)
  error correction
• Introduced Command Queuing and Command
  Overlapping to the world of IDE
• Bumped theoretical speeds to 66Mb/s

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ATA-5

• Merely a tweak for ATA-4
• bumped speeds to a theoretical 100Mb/s
• improved the command set

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ATA-6

• Increased the address bus to 64-bits
• this allows drives up to several hundred
  terabytes
• Bumped speed to a theoretical 133Mb/s
• New command set supports video streaming

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Serial ATA

• Takes IDE drives off a parallel cable
• data throughput increases dramatically
• Only a single device per cable prevents two
  devices from competing for bandwidth
• A very small footprint allows multiple ports to
  occupy less motherboard real estate than 40-pin
  connectors
• Differential gigabit technology speeds throughput

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Hard Disk Preparation

• Physical Installation
• Preparation of MBR and partitioning
• High-level format

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Installation Issues

• Masters and Slaves
• Modern computers have two IDE ports
• Each port can support two devices
• One device must be the master
• One device must be the slave
• IDE devices have jumpers
• Master, Slave or Cable Select settings

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More Installation Issues

• Two devices on one cable
• Both cannot be set to master or slave
• If set to cable-select, the position on the cable
  dictates which drive is master and which is slave

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A Word on Cable-Select

• 40-conductor Cables
• Not all are cable select. For a cable to be CS,
  the 28th wire will be clipped
• The middle connector becomes the master device
• 80-conductor Cables
• All are cable-select by default
• The end connector is the master

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Another Word on Cable-select

• If a cable-select cable is used, the drives
  should both be set to CS
• If the drives jumper setting conflicts with its
  position on the cable it will not be recognized
  at all

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Partitioning the Drive

• FDisk
• Used for all FAT file systems
• Prepares the MBR and allows the user to configure
  partitions
• 16-bit FDisk only supports FAT16
• 32-bit FDisk supports FAT16 and FAT32

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Formatting a Drive

• The high-level (OS) format maps out the FAUs on
  the drive
• The first format should NEVER be a quick format
• A standard format tests the integrity of each FAU
  before writing its information to FAT

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Hard Disk Maintenance

• Scandisk
• Checks file system for errors
• Cross-linked files
• Lost File Fragments
• FAT Entry Errors
• Can scan surface for bad sectors

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DeFrag

• Takes files that have been fragmented all over
  the drive and makes them contiguous
• Should be run in Safe Mode so fewer files are
  open by the OS
• Cannot be run if there are bad sectors. ScanDisk
  must be run first