
A P - 4 2 0 0    WESTERN DIGITAL
NO MORE PRODUCED                                      Native|  Translation
                                                      ------+-----+-----+-----
Form                 3.5"/HH               Cylinders    1280|  987|  987|  658
Capacity form/unform   212/      MB        Heads           8|   12|   10|   14
Seek time   / track  14.4/ 5.0 ms          Sector/track   41|   35|   42|   45
Controller           IDE / AT              Precompensation
Cache/Buffer            64 KB              Landing Zone
Data transfer rate    1.582 MB/S int       Bytes/Sector      512
                      5.000 MB/S ext
Recording method     RLL 2/7                        operating  | non-operating
                                                  -------------+--------------
Supply voltage     5/12 V       Temperature *C         5 50    |    -40 60
Power: sleep              W     Humidity     %         8 80    |      5 95
       standby            W     Altitude    km    -0.305  3.048| -0.305 12.192
       idle               W     Shock        g        10       |     50
       seek           8.5 W     Rotation   RPM      3610
       read/write     6.1 W     Acoustic   dBA        40
       spin-up       13.9 W     ECC        Bit   56
                                MTBF         h      50000
                                Warranty Month        24
Lift/Lock/Park     YES          Certificates     CSA,FCC,IEC950,UL1950,VDE


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WESTERN  WDAP4200 PIRANHA  INSTALLATION GUIDE S0830 79-000544-000

    +-------------------------------------------------------+
    |                                                       |XX 40-pin
    |                                                       |XX
    |                                                       |XX
    |                                                       |XX
    |                                                       |XX
    |                                                       |XX
    |                                                       |XX
    |                                                       |XX
 +-+|                                                       |X1
 |X||J4                                                     |+-+
 +-+|                                                       ||X|J8
 +-+|J5                                                     ||X|
 +-+|                                                       |+-+
   ++                                                       |XX
   ++LED                                                    |XX Power
    +-------------------------------------------------------+




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                      J   U   M   P   E   R   S
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WESTERN  WDAP4200 PIRANHA  INSTALLATION GUIDE S0830 79-000544-000


 Jumper Setting
 ==============
 All Piranha AP4200 drives have at least two jumper blocks, J4 and J8.
 In addition, some revisions have a third jumper J5.

 J4 is located next to the internal LED, behind the factory installed
 faceplate. J4 controls LED options and provides a connection for an
 external activity LED.

 J5 if present, is located next to J4. It provides an alternative
 connection for an external activitely LED.

 J8 is located next to the 40-pin connector. J8 defines information
 about the number and type of hard drives installed in the system.

 The Piranha drive is supplied factory-configured for the most common
 systems. If you need to change the standard Piranha settings for use
 in your system, use jumper shunts, which are available from your
 dealer.


 J4/J5 LED
 ---------
 The J4 jumper pins determine the color of the Piranha's internal LED
 and provide a connection for an external activity LED to the drive.

  LED+-+ J5 +7531+J4    To configure the internal LED as green, place
     |x|+--+|oooX|      a jumper shunt over J4 pins 1 and 2. This is
     | ||**||oooX|      the standard factory setting, and the drive is
  ---+-++--++8642+-     supplied with a jumper shunt on these pins.


  LED+-+ J5 +7531+J4    To configure the internal LED as red, move the
     |x|+--+|ooXo|      jumper shunt from pins 1 and 2 to pins 3 and
     | ||**||ooXo|      4.
  ---+-++--++8642+-

  LED+-+ J5 +7531+J4    To install an external activity LED from the
     |x|+--+|oXoo|      system, connect the positive lead (anode) of
     | ||**||oXoo|      the LED to pin 5 and the negative lead
  ---+-++--++8642+-     (cathode) to pin 6.
                        If you are using the WD 5.25 Kit, refer to the
                        instructions in the Kit.

  LED+-+ J5 +7531+J4    Some Piranha models include two additional
     |x|+--+|*ooo|      pins, 7 and 8, on the J4 jumper block. These
     | ||**||*ooo|      pins are reserved and should remain unjumper-
  ---+-++--++8642+-     ed.


  LED+-+ J5 +7531+J4    The J5 jumper, if present, is an alternative
     |x|+--+|oooo|      connector for an external activity LED. J5 is
     | ||**||oooo|      a two-pin 2mm connector.
  ---+-++--++8642+-


 J8 Master/Slave Configuration
 -----------------------------
     SINGLE
     ------531-+     The Piranha drive is factory-set for single drive
     oooo  ooo |J8   installation. If you are installing is as the
    ooooo  ooo |     only intelligent drive in your system, you do not
    -------642-+     need to install any jumper shunts.

     DUAL (MASTER)
     ------531-+     To designate the Piranha drive as the master,
     oooo  Xoo |J8   place a jumper shunt on pins 5-6.
    ooooo  Xoo |
    -------642-+

     DUAL (SLAVE)
     ------531-+     To designate the Piranha drive as the slave,
     oooo  oXo |J8   place a jumper shunt on pins 3-4.
    ooooo  oXo |
    -------642-+

     RESERVED
     ------531-+     Jumper pins 1 and 2 are reserved and should
     oooo  oo* |J8   remain unjumpered.
    ooooo  oo* |
    -------642-+



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WESTERN  WDAP4200 PIRANHA  INSTALLATION GUIDE S0830 79-000544-000


 Notes on Installation
 =====================

 Installation Options
 --------------------
 There are a number of installation options depending on your current
 system components and configuration.

 - If your system has a 40-pin connector on the motherboard, the
   Piranha drive is cabled directly to the motherboard.

 - If your system does not have a 40-pin connector on the motherboard,
   you need to install an adapter card and connect the hard drive to
   the connector on the adapter card.

 - If you are installing the Piranha drive as your second hard drive
   (dual installation,) the hard drives need to be daisy-chained to-
   gether using a daisy-chain cable. One connector to the adapter card
   or motherboard, and the other two attach to the drives.

 If you need to install an adapter card, your floppy drive(s) can
 also be connected to an adapter card with floppy support. This
 allows you to remove the floppy controller card from your system to
 create space for other cards you may want to add.

 The Piranha drive is not compatible with non-intelligent drives such
 as an ST-506 hard drive using a standard AT controller. If you have
 an ST-506 drive, you need to remove it and the AT controller card
 before installing the Piranha drive.

 You need a 40-pin host interface cable, not more than 18 inches long.

 You may need to use a power Y-adapter if you are installing the
 Piranha drive as a second hard drive and you do not have two internal
 power connectors. This adapter can be purchased through your computer
 supplier.

 If you are installing the Piranha intelligent drive in a 5-1/4" drive
 bay, you need a 5-1/4" frame. This frame mounts on the drive and
 adapts it to the larger bay. Western Digital offers a 5.25 Kit, which
 may be purchased from your dealer.

 If your system does not have a 40-pin connector on the motherboard,
 you need an adapter card to connect the drive. Usually, replacing an
 ST-506 drive requires the use of an adapter card.

 In dual drive installations, you must use a 40-pin host interface
 cable with three connectors, and daisy-chain the two drives to the
 motherboard or adapter card.

 Dual installations require a master/slave configuration, where one
 drive is designated as the secondary (slave) drive. The Piranha drive
 is compatible in dual installations with other intelligent drives
 that support the industry-standard master/slave configuration.

 If you have a Western Digital XT Controller and an ST-506 drive, you
 may retain the drive in the system by reconfiguring the XT controller
 for secondary drive. This is the only configuration that allows you
 to use both a Piranha drive and an ST-506 drive in the same system.

 CAUTION
 You may damage the Piranha drive if the interface cable is not
 connected properly. To prevent incorrec connection, use a cable that
 has keyed connectors. The female connector on the interface cable
 chould have a plug in position 20.


 Mounting Screws
 ---------------
 Mount the Piranha drive and frame to the drive bay using 6-32 screws
 (3/16"). Be sure to use the correct size screws. Do not install the
 screws past six threads. Screws that are too long will damage the
 Piranha drive.


 Power Connectors and Cables
 ---------------------------
 Power Connector         4 Pin (AMP P/N 770671-1 or equivalent)
 Mating Connector        Body (AMP 1-480424-0 or equivalent)
 Power Cable Wire Gauge  18 AWG



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                      F   E   A   T   U   R   E  S
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WESTERN  WDAP4200 PIRANHA  INSTALLATION GUIDE S0830 79-000544-000


 Overview
 --------
 The Western Digital Piranha AP4200 is a 212-MByte intelligent disk
 drive suitable as a new, upgrade, or replacement drive for installa-
 tion in your IBM PC/AT or compatible system. The Piranha hard drive
 is an intelligent drive, which means that the hard disk has the
 controller circuitry and 40-pin connector attached directly to the
 drive and doesn't require a slot-mounted controller card.

 Because of its compact, half-height size, the Piranha drive is easily
 incorporated into the newest systems, It has been designed for high-
 speed desktop PCs, CAD/CAM, engineering workstations, network file
 servers, and desktop publishing. The Piranha is a 3-1/2" drive that
 can also be used in a 5-1/4" drive bay with a drive frame available
 from your dealer.


 CAUTION
 Your intelligent drive is preformatted (low-level), and defect free.


 Seek Time
 ---------
       +----------------------------------+--------+
       |                                  | AP4200 |
       +----------------------------------+--------+
       |Track-to-Track         msec. typ. |   5    |
       +----------------------------------+--------+
       |Average                msec. typ. |  14.4  |
       |                       msec. max. |  25    |
       +----------------------------------+--------+
       |Latency                msec. avg. |   8.31 |
       +----------------------------------+--------+



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WESTERN   TIPS

 WESTERN DIGITAL 3.5-INCH DRIVES FREQUENTLY ASKED QUESTIONS
 ----------------------------------------------------------
 1) Will a Caviar drive work in my system?
   If your computer is 100% AT compatible and has either a 40-pin AT
   IDE interface on the motherboard or an IDE controller card with a
   40-pin data cable.

 2) What are the master/slave jumper settings on Western Digital
    drives?
    All Western Digital drives are configured the same. On the back of
    the drive between the 4-pin power connector and the 40-pin data
    connector, there is a jumper block J8 consisting of 6 pins.
    Western Digital hard drives are shipped with a jumper shunt in the
    neutral storage position (across pins 5 and 3) for future dual
    drive use.

 - If you are installing the Western Digital hard drive as the only
   hard drive in your system, leave the jmper shunt in the neutral
   storage posiition. Jumper shunts are not required for single hard
   drive installations.

 - To designate the Western Digital hard drive as the master (C:),
   place a jumper shunt on pins 5-6

 - To designate the Western Digital hard drive as the slave (D:),
   place a jumper shunt on pins 3-4.

 3) What are the drive type and the drive parameters in the CMOS, for
    Western Digital drives?
    On top of the drive, the number of cylinders, heads and sectors
    per track are printed on the label. Precomp and L-zone should be
    set equal to the drive's cylinder count + 1. Select user type or
    custom type (typically type 41 or 42) for your drive. This will
    allow you to type in the parameters. Older systems that do not
    offer a user type can either upgrade the system BIOS or set the
    drive to drive type 1 (which should be a smaller drive size), and
    run Ontrack Disk Manager from A drive to get the full capacity of
    the drive. If you do not follow one of these procedures and your
    system is pre-1994, you will be limited to the largest size drive
    your BIOS will allow.

 4) What is the Ontrack Disk Manager software that came with my drive
    and what does it do?
    Ontrack Disk Manager is the original hard disk installation
    package that will initialize, partition, and prepare your hard
    drive for use. Ontrack Disk Manager also allows you to access the
    full capacity of the drive even when your system BIOS can't. It is
    compatible with 32-bit disk access.

 Note: Ontrack Disk Manager must be installed from floppy drive A. If
 your A drive is a 5.25-inch floppy drive, copy the contents of your
 Ontrack Disk Manager disk to a formatted 5.25-inch disk and re-run
 Ontrack Disk Manager.

 5) I just installed Ontrack Disk Manager on my Caviar drive and tried
    to install DOS. DOS attempted to write to my drive and it
    formatted my drive back to 528 MB which is my BIOS limitation. How
    do I install DOS and still get the full capacity of my drive?
    After Ontrack Disk Manager installation, you must create an
    Ontrack Disk Manager rescue disk. There are two ways of
    accomplishing this:

 OPTION 1:
 - Create a clean DOS bootable disk.

 - Copy 2 files from the Ontrack Disk Manager disk to your bootable
   disk: XBIOS.OVL, and DMDRVR.BINs Create a CONFIG.SYS file on this
   bootable disk with these 3 lines: DEVICE=DMDRVR.BIN FILES=35
   BUFFERS=35

 - Remove the floppy and reboot the system.

 - When you see the message "Press spacebar to boot from diskette",
   press the spacebar (system halts).

 - Insert the rescue disk in the A: drive.

 - Press any key (system resumes boot process).

 - At the A: prompt, remove rescue disk, insert DOS installation disk
   and type SETUP.

 - You can now install DOS without overwriting the Ontrack Disk
   Manager files.

 OPTION 2:

 - Create a clean DOS bootable disk.

 - Insert Ontrack Disk Manager disk in the A: drive.

 - At the A prompt, type: DMCFIG/D=A:. You will be prompted to insert
   a bootable floppy in the A: drive.

 - Follow the prompts on the screen. Ontrack Disk Manager will ask you
   to change disks a few times.

 - Continue until Ontrack Disk Manager is finished.

 - Remove the floppy and reboot the system.

 - When you see the message "Press spacebar to boot from diskette".
   Press the spacebar (system halts).

 - Insert the rescue disk in A drive.

 - Press any key (system resumes boot process).

 - At A prompt, remove rescue disk, insert DOS installation disk and
   type SETUP.

 - You can now install DOS without overwriting the Ontrack Disk
   Manager files.

 6) CHKDSK or SCANDISK reports a few bad sectors. How do I go about
    fixing the problem.
    You can use the Western Digital defect management utility WDATIDE.
    One of its options is the comprehensive surface analysis. This
    procedure will mark all grown defects bad if indeed there are any
    and it will compensate for the lost capacity by utilizing spare
    tracks.

 Note: This utility is data destructive. Back up all data on the drive
 before using it. Due to the thoroughness of this operation, WDATIDE
 can take quite a bit a time depending on the capacity of your drive.

 7) Do I have to do anything with my original drive when adding a new
    drive to my system?
    Yes, one hard drive must be designated as the master drive
    (preferably the newer, faster drive) and the other must be
    designated as the slave drive. Typically, most drives need to have
    a jumper placed on them to specify the Master or Slave position.
    For information on non-Caviar hard drives, please contact the
    appropriate manufacturer.

 8) I installed my new drive and entered the drive parameters in the
    CMOS, but the drive will not boot or it displays the message "HDD
    controller failure."
    Your drive must be partitioned and formatted before it will be
    bootable. If your system will support drives larger than 528 MB,
    and you have a copy of MS-DOS or PC-DOS version 5.0 or greater,
    insert the setup diskette in your floppy drive and turn on your
    computer. Follow the prompts and DOS will partition and format the
    drive for you.

 If you do not have a copy of MS-DOS or PC-DOS version 5.0 or greater,
 you will need to boot from a bootable disk and then run the FDISK
 command to partition your drive, and then format the drive using the
 DOS FORMAT command. After running format, you should be able to
 reboot your computer from your hard drive.

 9) How can I use the full capacity of my Caviar drive of 540 MB or
    greater?
    You can use Ontrack Disk Manager to obtain full capacity if your
    system does not support LBA mode. If your system does support LBA
    mode, you can enable LBA in your CMOS setup utility.

 10) How can I get 32-Bit Disk Access in Windows on my Caviar AC2540,
     AC2700 or AC31000 in Windows 3.1x? If your BIOS supports the
     drive at full capacity (i.e., the BIOS supports Logical Block
     Addressing) you use WDCDRV.386, Western Digital's FastDisk device
     driver. This driver is contained in a file named WIN31.EXE
     available for downloading from our bulletin board (714/753-1234),
     our Web server (WWW.WDC.COM), our FTP site (FTP.WDC.COM), our
     forum on the Microsoft Network (Go word WDC), and our forum on
     America On-line (keyword WDC). If your BIOS does not support LBA
     mode and you have installed your drive using Ontrack Disk Manager
     (v6.03 and above), run DMCFIG to install WDCDRV.386 and obtain
     32-Bit Disk Access.

 11) My drive will not spin up or spins down after a few seconds.
     This is a drive failure. Return the drive to the distributor or
     contact a technical support representative to receive a Return
     Materials Authorization (RMA).

 12) CMOS, FDISK and File Manager in Windows report less than the
     capacity of my new drive, but CHKDSK reports the right number of
     bytes. Which is correct?
     Setup (CMOS) and FDISK use a binary definition of a megabyte
     which is calculated at 1,048,256 bytes per megabyte. All hard
     drive manufacturers and the DOS CHKDSK utility use a decimal
     definition of a megabyte which is calculated at 1,000,000 bytes
     per megabyte. This is why some utilities show 515 MB for a 540
     megabyte drive and some show the actual number.

 13) How Can I install OS/2 for Windows, OS/2 3.0 WARP, Windows NT
     3.5x or Windows 95 on my drive which was initially installed
     using Ontrack Disk Manager?
     If you have Ontrack Disk Manager version 6.03, 6.03a, or 6.03b,
     download the file named DMPATCH.EXE from Western Digital's online
     services: ftp site: ftp.wdc.com

 World Wide Web Site: http://www.wdc.com/
 Microsoft Network (MSN) - Go word WDC
 America Online (AOL) - Keyword: Western Digital
 Western Digital's BBS at (714) 753-1234
 This file has the latest Ontrack Disk Manager drivers which will
 allow you to install OS/2 version 2.1x, OS/2 WARP, Windows NT 3.5x
 or Windows 95 on your hard drive. Please read the included readme
 file with this file for further detail.

 14) My drive will work as a slave but not as a master (or vice-
 versa).
 Check master/slave jumpers on all drives. Also, some drive's speed
 and timing differ drastically as to the initial spinup sequence. This
 might confuse the system and cause one of the drives not to be
 recognized. The best solution for this situation is to exchange
 drives (make the master a slave and vice-versa).

 15) My drive will not partition when I run FDISK. It hangs the system
     or it displays the message: "Runtime error."
     This is usually caused by corruption or damage to track zero. Use
     the Western Digital utility WDFMT to format the drive. If that
     does not help, call Western Digital Technical support at
     1-800-ASK-4-WDC to get further instructions.

 16) Can a hard drive be mounted on it's side, edge, or upside down?
     Drives can be mounted on any side but it is preferable to mount
     the drive right side up. It is also important to use all four
     screws to hold the drive firmly in place.


 Self-Monitoring, Analysis, and Reporting Technology (S.M.A.R.T.)
 ----------------------------------------------------------------
 S.M.A.R.T. enables a drive's internal status to be monitored through
 diagnostic commands at the host level.

 The Caviar AC21600, AC32100 and AC32500 drives monitor read error
 rate, start/stop count, spin-up retry count, and drive calibration
 retry count. All of these attributes are updated and stored on the
 hard drive in the reserved area of the disk. The hard drive also
 stores a set of attribute thresholds that correspond to the
 calculated attribute values. Each attribute threshold indicates the
 point at which its corresponding attribute value achieves a negative
 reliability status.
 ====================================================================

  QUESTION
  Which hard drive specification is most important to overall
  system performance ?

 - Host Transfer Rate
 - Drive RPM (revolutions per minute)
 - Disk Transfer Rate (Media Rate)
 - Seek Time
 - Cache Size
 - PC Data Handling
 - All of the above

 Answer
 The correct answer is actually a combination of "all of the above,"
 keeping in mind most of the above specifications are interrelated
 when it comes to optimizing system performance.

 The pie chart illustrates the relative influence of factors affecting

 drive performance during a typical random I/O operation (reading
 and writing to a hard drive).

 The major determinate of hard drive performance is mechanical
 factors which are one hundred times slower than the high-speed
 electronics contained in a drive.


 Factors Affecting Hard Drive Performance
 (In their relative order of importance)

 MECHANICAL LATENCIES
 Mechanical Latencies include both Seek Time and Rotational
 Latency. The seek time is a measure (in milliseconds) of how
 fast the hard drive can move its read/write heads to a desired
 location. Rotational latency is a measure of the average time
 (also in milliseconds) the read/write heads must wait for the
 target sector on the disk to pass under them once the read/write
 heads are moved to the desired target track.

 Mechanical latencies are the main hindrance to higher performance
 in modern Enhanced IDE (EIDE) hard drives. The time delays of
 mechanical latencies are one hundred times higher than
 electronic (non-mechanical) latencies associated with the
 transferring of data. Therefore, reducing mechanical latencies
 (a lowering of seek time and rotational latency) should be the
 top consideration in improving hard drive performance.

 RPM
 This is the rotational speed of the media (disk), also referred
 to as the spindle speed. Hard drives only spin at one constant
 speed. Typical speeds are 3600 to 3880, 4500, and 5200 to 5400
 revolutions per minute. The slower the RPM, the higher the
 Mechanical Latencies. Disk RPM is a critical component of hard
 drive performance because it directly impacts the rotational latency
 and the Disk Transfer Rate explained below.

 DISK TRANSFER RATE
 The Disk Transfer Rate (sometimes called media rate) is the
 speed at which data is transferred to and from the disk media
 (actual disk platter) and is a function of the recording frequency.
 Typical units are bits per second (BPS), or bytes per second.
 Modern hard disks have an increasing range of Disk Transfer
 Rates from the inner diameter to the outer diameter of the disk.
 This is called a "zoned" recording technique.

 The key media recording parameters relating to density per platter
 are Tracks Per Inch (TPI) and Bits Per Inch (BPI). A track is a
 circular ring around the disk. TPI is the number of these tracks
 that can fit in a given area (inch). BPI defines how many bits
 can be written onto one inch of a track on a disk surface. To
 greatly simplify, the Disk Transfer Rate (the rate at which data
 is read and written to the disk) is dependent upon the speed of
 the disk (RPM) and the density of the data on the disk (BPI).
 Even most modern, high-speed, 5000 RPM hard drives are generally
 limited to a maximum Disk Transfer Rate of approximately 9 to 10
 MB per second. This specification is critical to performance and
 must be weighed carefully against such electronic latencies as
 Mode 3 PIO and Mode 4 PIO host transfer rates explained below.

 PC DATA HANDLING
 After the data moves down the IDE cable from the drive to the host
 interface, there are several factors that can affect drive
 performance over which the hard drive has no control. PC Data
 Handling is independent from the hard drive and very dependent
 upon the CPU type and speed, the BIOS overhead (how the system
 issues commands to the hard drive), speed and size of the system
 RAM and RAM cache, CPU-to-memory speed, and storage subsystem
 performance. PC Data Handling is also affected by the caching
 methods of such software applications as SMARTDRIVE, 32-bit
 disk access operating system drivers, etc.

 HOST TRANSFER RATE
 The speed at which the host computer can transfer data across the
 IDE or EIDE interface. Processor Input/Output (PIO) modes and
 Direct Memory Access (DMA) modes are defined in the ATA-2 industry
 specification as follows:

 Mode 3 PIO  11.1 MB/sec
 Mode 4 PIO  16.6 MB/sec
 Mode 1 DMA  13.3 MB/sec
 Mode 2 DMA  16.6 MB/sec

 Modern host computer systems usually support most of the above
 modes. Faster Host Transfer Rates in the future will use multi-word
 DMA modes as the industry will not support any future PIO mode
 standards beyond mode 4.

 The computer system manufacturer is responsible for implementing a
 Host Transfer Rate that is high enough to ensure that the host
 computer is not the performance bottleneck. Implementing
 increasingly higher Host Transfer Rates without corresponding
 increases in Disk Transfer Rates on the hard drive will not result
 in increased drive performance.


 Cache Buffer Size - Is Bigger Always Better ?
 A Cache Buffer is similar to a water glass. When you are writing
 to a hard drive, the host computer fills the glass and the disk
 media empties it. If you are reading data from a hard drive, the
 disk media fills the glass and the host computer empties it.

 The reason that a bigger cache buffer is not always better
 (or faster) is because the host computer (with Mode 4 PIO or
 Mode 2 DMA capabilities) can empty or fill the glass much faster
 than the hard drive can empty or fill it. When the host system can
 transfer data in or out of the cache buffer faster than the media
 rate, a larger buffer size becomes irrelevant because the host
 system is always "waiting" for the hard drive.

 Western Digital hard drives are designed with cache buffer sizes
 that are matched to the Disk Transfer Rate capabilities of the
 drive and the Host Transfer Rates of modern computer systems. All
 of our drives are benchmarked with various cache buffer sizes to
 verify that the most cost-effective and performance-effective
 cache size is implemented.


 Confusion Over Mode 4 and Mode 2 DMA
 The Enhanced IDE program created the long-range road map for
 performance enhancements which included faster disk and host
 transfers, Mode 3, Mode 4, Mode 2 DMA, etc. Currently, computer
 systems and hard drive controller silicon have most of the elements
 needed to implement Mode 4 PIO or Mode 2 DMA (a 16.6 MB/sec Host
 Transfer Rate). However, to take advantage of these performance
 modes, physical drive architecture must also make some performance
 improvements in the area of Mechanical Latencies and Disk Transfer
 Rate (media rate) as defined earlier.

 Some competitors, in their eagerness to supply a new feature, are
 prematurely marketing Mode 4 and Mode 2 DMA. While their drive
 controller silicon supports these modes (which is very easy and
 inexpensive to implement), spindle speeds (RPM), rotational latency,
 bit density, and other factors have not yet been improved (these
 being very difficult and costly). The result is hard drives which
 have the electronic capability to do Mode 4 and Mode 2 DMA transfer
 rates, but can't take advantage of these modes due to the slower
 Disk Transfer Rate of the drive.

 Western Digital will not be implementing Mode 4 or Mode 2 DMA on
 older drive products as the host systems into which these drives
 are designed are not electrically capable of these data transfers,
 nor are the Disk Transfer Rates on these drives beyond current Mode
 3 capabilities. As next generation systems are introduced, they will
 be paired with next generation drives. Those drives will require
 and offer true Mode 4 / Mode 2 DMA capability from a total drive
 architecture standpoint.
 =====================================================================
 AC2540/2635/2700/2850/21000/31000/31200/31600

 Windows 95 Operating System Addendum
 ------------------------------------
 The information in this addendum supersedes that supplied in Windows
 95 section on pages 35 and 36 of this manual. Please refer to thos
 addendum for Windows 95 questions.

 Although Windows 95 is capable of recognizing the full capacity of
 hard drives larger than 528 MB in systems with a translating BIOS,
 some restrictions apply to systems without a translating BIOS.


 For Systems With a Translating BIOS
 -----------------------------------
 Enter your CMOS setup and select a drive type that will recognize the
 full capacity of your drive. This is usually done by selecting the
 auto config drive tape. The boot partition can be set up to be as
 large as the full capacity of your hard drive.


 For Systems Without a Translating BIOS
 --------------------------------------
 Enter your CMOS setup and select a user defined drive type. Enter
 these parameters: cylinders = 1024, heads = 16, sectors = 63. Your
 system's total disk space will be limited to a maximum of 528MB.

 If you want your system to utilize more than 528 MB of disk space,
 you must use Ontrack's Disk Manager software (or a similar third-
 party installation software).


 Installing Windows 95 on a Hard Drive with Ontrack Disk Manager
 Already Installed
 ---------------------------------------------------------------
 The Windows 95 installation program will analyze your computer
 system and install seamlessly with Ontrack Disk Manager.


 Computer Systems with Windows 95 Already Installed
 --------------------------------------------------
 If you are installing a Western Digital hard drive and Ontrack Disk
 Manager on a computer system with Windows 95 already installed, you
 must install Ontrack Disk Manager as described here.

 Enter your CMOS setup and select a user defined drive type. Enter
 these parameters for drives with capacities over 528MB:
         Cylinders = 1024, Heads = 16, Sectors = 63.

 Save these changes and reboot your computer.

 1. Select the Start icon from the Windows 95 main screen.
    DO NOT open an MS-DOS menu from Win 95 to install Ontrack Disk
    Manager.

 2. Choose the Shut Down option.

 3. Select Resatrt Computer in DOS mode. When your computer restarts,
    you should be at the DOS prompt.

 4. Install Ontrack Disk Manager.

 Windows 95 will noe recognize the full capacity of your hard drive
 and run in 32-bit disk access mode for optimum performance.


