Integrated Drive Electronics AT Attachment ( IDE / ATA )

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Integrated Drive ElectronicsAT Attachment ( IDE
/ ATA )
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Some numbers

• Desktop PC
• 80 500 GB
• 7200 10000 rpm (laptop 5400rpm)
• 50 150 MB/s
• Server
• 70 300 GB
• 10000 15000 rpm
• 320 MB/s

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ST-506 interface

• 1980 ST-506 interface
• Encoding scheme MFM (Modified Frequency
  Modulation), still used in 1,44 MB floppy
• Data rate 5 megabits per second
• No logic on the disk dumb disk
• 2 cables
• 20 pins cable for data
• 34 pins cable for control signals

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ESDI interface

• Enhanced Small Device Interface
• Mid-1980s Late 1980s
• Some drive controller functions moved to the hard
  disk
• More reliable
• 24 Mbits/seconds (practice 12Mbits/second)

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IDE interface

• Late 1980s
• ATA, ATA/ATAPI, EIDE, ATA-2, Fast ATA, ATA-3,
  Ultra ATA, Ultra DMA, ...
• Used by a majority of the current PCs
• Good performance at relatively low cost
• Competitor SCSI and SATA (successor)

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Overview IDE/ATA Interface

• 1986 Compaq, Western Digital and Control Data
  Corporation (now Seagate).
• Extension of the ISA system bus
• 16 bits wide (till today !)
• 2 drives on each IDE/ATA channel
• Special signalling used to not interfere
• 1990 first ANSI standard for IDE/ATA

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ATA-1 standard

• Published in 1994, withdrawn as ANSI standard in
  1999
• Two hard disks master and slave
• PIO Modes PIO mode 0, 1 and 2
• DMA Modes single word DMA modes 0, 1 and 2 and
  multiword DMA mode 0
• No support for ATAPI, block mode transferts,
  Ultra DMA, ...

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PIO Programmed IO
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DMA modes
DMA was not supported by the first version of
Windows 95 !
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Ways of doing DMA transferts

• Conventional DMA
• AKA third party
• DMA controller on the motherboard coordinates
• Slow, still the same controller since the early
  days of the PC
• Tied to the ISA bus

• Bus Mastering DMA
• AKA first party
• Disk and Memory communicate directly
• Low CPU Utilization
• Became popular with Ultra DMA

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ATA-2 Standard

• Backward compatible
• Faster PIO Modes 3 and 4
• Faster DMA modes multiword 1 and 2
• Commands to do block transfers are added
• Logical Block Addressing (LBA)
• Supported by the harddisk
• BIOS must support LBA
• Improved Identify Drive Command

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Block Mode

• Block Mode (option in BIOS)
• Performance enhancement
• Allows grouping of multiple read or write
  commands over IDE/ATA Interface so that they can
  be handled on a single interrupt.
• Newest drives allow transferts of 16-32 sectors
  with a single interrupt.
• CPU is less frequently interrupted gt performance
  is increased.

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LBA Logical Block Addressing

• Regular adressing (Standard CHS)
• Cylinder, head, sector address define location
• Extended CHS addressing
• Cylinder, head, sector address define location
• To break the 504 MB barrier (1024 cyl, 16 heads,
  63 sectors).
• Change the way the geometry appears
• LBA
• Each sector is assigned a unique sector number
  (0,1,2...,N-1). N is the total number of sectors
  on a given disk.
• Must be supported by the harddisk, System BIOS
  and Operating System
• No problem with 504 MB disk size barrier

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ATA-3

• Improved Reliability of the higher speed transfer
  modes. (cabling was low-perf 40 wire ribbon)
• SMART-Technology
• Self-Monitoring Analysis and Reporting Technology
• Security Mode password protect devices
• PIO Mode 5 never approved

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S M A R T

• Early warning system for pending drive problems.
• Sensors that monitor various aspects of the
  drives performance
• Predictable failures occur slowly over time and
  can be detected by monitoring temperature,
  current, time things take, ...
• Ex. Spindle motor bearing burnout
• Warning system only, not foolproof !

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S M A R T can monitor

• Head Flying Height A downward trend in flying
  height will often presage a head crash.
• Number of Remapped Sectors If the drive is
  remapping many sectors due to internally-detected
  errors, this can mean the drive is starting to
  go.
• ECC Use and Error Counts The number of errors
  encountered by the drive, even if corrected
  internally, often signal problems developing with
  the drive. The trend is in some cases more
  important than the actual count.
• Spin-Up Time Changes in spin-up time can reflect
  problems with the spindle motor.
• Temperature Increases in drive temperature often
  signal spindle motor problems.
• Data Throughput Reduction in the transfer rate
  of the drive can signal various internal
  problems.

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SFF-8020/ATA Packet Interface (ATAPI)

• Special protocol (ATAPI) to add support for
  non-disk-devices.
• Commands to ATAPI devices are sent in groups
  called packets.
• Much more complex than regular ATA.
• Resembles SCSI more than IDE in terms of its
  command set and operation.
• Special ATAPI driver used to communicate with
  ATAPI devices

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ATA/ATAPI-4

• ATAPI feature ATA (1998)
• Ultra DMA Modes 0,1 and 2 (16.7,25 and 33.3 MB/s)
• High Performance IDE Cable (80-conductor)
• In the end left optional for Ultra DMA modes
• Mandatory for ATA/ATAPI-5 (Starting with Ultra
  ATA/44)
• CRC (Cyclic Redundancy Checking)
• Command set was cleaned up

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Ultra DMA CRC

• Double transition clocking (data transferred on
  both rising and falling edges of the clock).
• CRC to improve integrity of this faster
  interface.
• Naming Ultra ATA/xx where xx is the speed of
  the interface.
• Disk with Ultra DMA mode 5 gt Ultra ATA/100

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ATA/ATAPI-5

• Published in 2000
• Higher speed DMA Modes 3 and 4 (44.4 and 66.7
  MB/s) by means of inerface speed-up.
• Mandatory 80-Conductor IDE cable
• Host can detect if 80-conductor cable is used
• Minor command changes, further cleanup

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ATA/ATAPI-6

• Published in 2002
• Ultra DMA mode 5 100MB/s
• LBA Address Size Expansion
• Harddisk noise reduction
• Specific command set for Audio and Video
  streaming
• ? SATA

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Summary of IDE/ATA Standards
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Sources

• http//www.storagereview.com/guide2000/ref/hdd/if/
  ide/index.html