
A C - 3 5 1 0 0    WESTERN DIGITAL
                                                      Native|  Translation
                                                      ------+-----+-----+-----
Form                 3.5"/HH               Cylinders        |10572|     |
Capacity form/unform  5163/      MB        Heads           6|   15|     |
Seek time   / track  11.0/ 3.0 ms          Sector/track     |   63|     |
Controller           IDE / ATA4            Precompensation
Cache/Buffer           256 KB DRAM         Landing Zone
Data transfer rate    8.000 MB/S int       Bytes/Sector      512
                     33.300 MB/S ext UDMA
Recording method     GCR8/9PRML                     operating  | non-operating
                                                  -------------+--------------
Supply voltage     5/12 V       Temperature *C         5 50    |    -40 60
Power: sleep          1.0 W     Humidity     %         5 80    |      5 95
       standby        1.5 W     Altitude    km    -0.300  3.000| -0.300 12.000
       idle           5.4 W     Shock        g        10       |    150
       seek           8.6 W     Rotation   RPM      5400
       read/write     5.4 W     Acoustic   dBA        38
       spin-up       24.4 W     ECC        Bit   72BIT REED SOLOMON,SMART
                                MTBF         h     350000
                                Warranty Month        36
Lift/Lock/Park     YES          Certificates     CSA,EN50082-1,EN60950,FCC,...

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                        L   A   Y   O   U   T
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WESTERN  AC12100/23200/24300/35100/36400 TE.RE.MANUAL 79-860030-002 97

  +---------------------------------------------------------+
  |                                                         |XX
  |                                                         |XX J2
  |                                                         |XX Inter-
  |                                                         |XX face
  |                                                         |XX
  |                                                         |.X
  |                                                         |XX
  |                                                         |XX
  |                                                         |XX
  |                                                         |XX
  |                                                         |X1
  |                                                         |+-+
  |                                                         || |J8
  |                                                         |+-1
  |                                                         |XX Power
  |                                                         |XX J3
  +---------------------------------------------------------+  1








                         J2                    J8           J3
    +39------------------------------------1++9-7-5-3-1++-------+
    |o o o o o o o o o o o o o o o o o o o o||o o o o o||O O O O|
    |o o o o o o o o o o   o o o o o o o o o||o o o o o||4 3 2 1|
  --+40------------------------------------2+10-8-6-4-2+++-+-+-++----
                                                         | | | +12V
                   (Pin 20 keyed)                        | | +- GND
                                                         | +--- GND
                                                         +----- +5V



**********************************************************************
                      J   U   M   P   E   R   S
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WESTERN  AC12100/23200/24300/35100/36400 TE.RE.MANUAL 79-860030-002 97

 Jumper setting
 ==============


 J8  Master/Slave/Cable Select Configuration
 -------------------------------------------

    +5-3-1+ Single (Neutral Position)
    |xxx o| Factory default. The jumper in this position has no effect
    |o o o| on single hard drive configurations.
    +6-4-2+


    +5-3-1+ Cable Select              +5-3-1+ Master Drive
    |o o X| option.                   |X o o| Configuration
    |o o X|                           |X o o| (Dual Drives)
    +6-4-2+                           +6-4-2+


    +5-3-1+ Slave Drive
    |o X o| Configuration
    |o X o| (Dual Drives)
    +6-4-2+


 The Caviar can be assigned as either a single, master, or slave
 drive.


 Jumper Settings
 ---------------
 The Caviar drive has a jumper block (J8) located next to the 40-pin
 connector on the drive. The Caviar can be assigned as either a
 single, master, or slave drive.

 Caviar drives are shipped with a jumper shunt in the neutral storage
 position (across pins 5 and 3).

 The additional foour pins on the 10-pin connector are RESERVED
 for future use.

 Single Drive Mode - If you are installing the Caviar drive as the
 only hard drive in the system, leave the jumper in the neutral
 storage position. Jumpers are not required for single drive
 installations. Note that even with no jumper installed, the Caviar
 checks the DRIVE ACTIVE/SLAVE PRESENT (DASP) signal to determine if a
 slave IDE drive is present.

 If you have a dual installation (two hard drives), you must designate
 one of the drives as the master and the other as the slave drive. The
 jumper pins on the J8 connector need to be configured for the dual
 installation.


 Master Drive Mode - To designate the drive as the master, place a
 jumper shunt on pins 5-6. With the Caviar configured as the master
 drive, the Caviar assumes that a slave drive is present. The jumper
 on pins 5-6 is optional if the slave drive follows the same protocol
 (Common Access Method AT Bus Attachment) as the WD Caviar drive.


 Slave Drive Mode - To designate the drive as the slave, place a
 jumper shunt on pins 3-4. When the Caviar is configured as the slave
 drive, the Caviar delays spin up for three seconds after power-up
 reset. This feature prevents overloading of the power supply during
 power-up.


 Cable Select (CSEL) - Caviar also supports the CSEL signal on the
 drive cable as a drive address selection. Place a jumper shunt on
 pins 1-2 to enable this option. When enabled, the drive address is 0
 (Master) if CSEL is low, or 1 (Slave) if CSEL is high.

 Do not install the CSEL jumper shunt when installing the Caviar drive
 in systems that do not support the CSEL feature.


 J3   DC Power and pin connector assignments
 -------------------------------------------
      +------------+   pin 1    +12 V
      | 4  3  2  1 |   pin 2    GND
      +------------+   pin 3    GND
                       pin 4    + 5 V


 Alternate Jumper Settings for Drives Larger than 2.1 GB
 =======================================================
 On initial boot, the system BIOs may lock up on drives that have
 more than 4095 cylinders (driver larger than 2.1 GB). Alternate
 jumper setting have been provided for the Caviar drives that are
 larger than 2.1GB to overcome this system BIOS limitation. These
 jumper settings cause the drive to report 4092 cylinders (instead of
 the usual 8912, 6,296, 11,184, or 7752) in Word 1 of the Identify
 Drive data.

 The true capacity is still reported in Word 54 and Word 60-61. All
 other Identify Drive data remains the same.

 NOTE
 Do not use these alternate jumper settings in Windows NT systems!

    +5-3-1+ Single Drive              +5-3-1+ Master Drive
    |X X o| Configuration             |X o X| Configuration
    |X X o|                           |X o X| (Dual Drives)
    +6-4-2+                           +6-4-2+


    +5-3-1+ Slave Drive
    |o X X| Configuration
    |o X X| (Dual Drives)
    +6-4-2+

 If these jumper settings are invoked, the cable select option is not
 avaiable.



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                      I   N   S   T   A   L   L
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WESTERN  AC12100/23200/24300/35100/36400 TE.RE.MANUAL 79-860030-002 97

 Notes On Installation
 =====================

 Installation direction
 ----------------------

     horizontally                           vertically
   +-----------------+             +--+                       +--+
   |                 |             |  +-----+           +-----+  |
   |                 |             |  |     |           |     |  |
 +-+-----------------+-+           |  |     |           |     |  |
 +---------------------+           |  |     |           |     |  |
                                   |  |     |           |     |  |
                                   |  |     |           |     |  |
 +---------------------+           |  +-----+           +-----+  |
 +-+-----------------+-+           +--+                       +--+
   |                 |
   |                 |
   +-----------------+

 The drive will operate in all axis (6 directions).


 Orientation
 -----------
 The Caviar can be mounted in the X, Y, or Z axis depending upon the
 physical design of your system. It is recommended that the drive be
 mounted with all four screws grounded to the chassis.


 Screw Size Limitations
 ----------------------
 The Caviar is mounted to the chassis using four 6-32 screws.
 Recommended screw torque is 5 in-lb. Maximum screw torque is 10
 in-lb.

 Caution: Screws that are too long will damage circuit board
 components. The screw must engage no more than six threads (3/16
 inch). Side mounted screws should engage a maximum of .188 inches
 (3/16"). Bottom mounted screws should engage a maximum of .250
 inches (1/4").


 Grounding
 ---------
 It is recommended that the drive be mounted with all four screws in
 the side grounded to the chassis. The drive must be grounded with at
 least one mounting screw.

 Side mounting: Use four metal screws.

 Top face mounting: Use four metal screws.


 Cabling and Installation Steps
 ------------------------------
 Make sure your interface cable is no longer than 18 inches (including
 daisy chaining) to minimize noise that is induced on the data and
 control buses. When connecting two drives, use a daisy-chain cable
 that has three 40-pin connectors. Connectors should be placed no more
 than six inches from the end of the cable. If only one drive is
 connected, it should be placed on the end of the cable.

 Caution: You may damage the Caviar drive if the interface cable is
 not connected properly. To prevent incorrect connection, use a cable
 that has keyed connectors at both the drive and host ends.
 Pin 20 has been removed from the J2 connector. The female connector
 on the interface cable should have a plug in position 20 to prevent
 incorrect connection. Make sure that pin 1 on the cable is connected
 to pin 1 on the connectors.


 Interface Pin 39 HDASP (I/O) Drive Active/Slave Present
 -------------------------------------------------------
 This open collector output is a time-muliplexed signal indicating
 drive active or slave present. At reset, this signal is an output
 from the slave drive and an input to the master drive, showing that a
 slave is present. For all times other than reset, HDASP- is asserted
 by the master and slave drives during command execution.


 Power Connectors and Cables
 ---------------------------
 Power Connector           4-pin AMP P/N 84069-1 or equivalent

 Mating Connector          Body  AMP 1-480424-0 or equivalent
                           Pins  AMP 60619-4 or equivalent

 Power Cable Wire Gauge    18 AWG (or heavier)



**********************************************************************
                      F   E   A   T   U   R   E  S
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WESTERN  AC12100/23200/24300/35100/36400 TE.RE.MANUAL 79-860030-002 97

 General Description
 -------------------
 Western Digital's latest generation of high-performance WD Caviar
 drives, the AC12100/23200/24300/35100 and AC36400 Enhanced IDE hard
 drives, set new standards for storage, performance and reliability.

 With storage capacities up to 6.4 gigabytes, these workhorse WD
 Caviar drives are engineered to handle today's most storage-intensive
 desktop, workstation, multimedia and internet applications.


 Advanced Product Features
 -------------------------
 - CacheFlow5 - Western Digital's unique, fifth-generation caching
   algorithm evaluates the way data is read from and written to the
   drive and adapts on-the-fly to the optimum read and write caching
   methods. CacheFlow5 minimizes disk seeking operations and the
   overhead due to rotational latency delays.

   CacheFlow5 supports sequential write cache.
   Incorporating write cache with other CacheFlow5 features enables
   the user to cache both read data as well as write data. Multiple
   writes can now be held in the cache and then written collectively
   to the hard disk later. Data is held in the cache no longer than
   the time required to write all cached commands to the disk.

   CacheFlow5 constantly evaluates not only the size of the read data
   request but the type of data request, that is, whether the
   data request is sequential, random, or repetitive. CacheFlow5
   selects the appropriate caching mode for optimum system
   performance.

 - Advanced Host Transfer - The AC12100/23200/24300/35100/36400
   support Mode 4 PIO (16.6 MB/s) and Mode 2 multi-word DMA (16.6
   MB/s) as defined by the ATA-4 standards. To achieve Mode 4 PIO
   burst transfers, hard disk drives must be able to throttle the
   host via the IORDY signal.

   Systems typically require a high-speed VL or PCI local bus in
   order to support Mode 4 PIO.

 - High-Speed DMA Capability - DMA Read and DMA Write commands are
   ATA-4 compatible and provide significant improvement in CPU
   bandwidth over conventional PIO data transfers. The system CPU
   is free to accomplish other tasks while the Caviar drive
   transfers data directly to/from system memory.

 - Power Conservation - The AC12100/23200/24300/35100/36400 supports
   the ATA-4 power management command set. This command set allows the
   host to reduce the power consumption of the drive by issuing a
   variety of power management commands.

 - Block Mode - ATA-4 compatible Read Multiple and Write Multiple
   commands are supported. Block mode increases overall data
   transfer rates by transferring more data between system
   interrupts.

 - Logical Block Addressing (LBA) - The AC12100/23200/24300/35100/
   36400 support both LBA and CHS-based addressing. LBA is included
   in advanced BIOS and operating system device drivers and ensures
   high-capacity disk integration.

 - Automatic Head Parking - Head parking is automatic with Caviar
   drives. On power down, the heads retract to a safe, non-data
   landing zone and lock into position, improving data integrity and
   resistance to non-operational shock.

 - Advanced Defect Management - These Caviar drives are preformatted
   (low-level) at the factory and come with a full complement of
   automatic defect management functions. Extensively tested during
   the manufacturing process, media defects found during intelligent
   burn in are mapped out with Western Digital's high performance
   defect management technique. No modifications are required
   before installation.

 - Embedded Servo Control - These Caviar drives feature an embedded
   servo concept as the means of providing sampled position feedback
   information to the head position servo system. Servo bursts are
   located along a radial path from the disk center, ensuring that
   head positioning data occurs at constant intervals. This high
   sampling rate supports the high frequency servo bandwidth
   required for fast access times as well as highly accurate head
   positioning. The embedded servo concept provides the means of
   generating accurate feedback information without requiring a full
   data surface as would a dedicated servo control concept.

 - Dual Drive Operation - These Caviar drives support dual drive
   operation by means of a "daisy chain" cable assembly and
   configuration options for master or slave drive designation. They
   also supports Cable Select (CSEL) for master or slave designation.

 - Universal Address Translation - These Caviar drives provide a
   linear disk address translator to convert logical sector
   addresses to physical sector addresses which provides for easy
   installation and compatibility with numerous drive types.

 - Guaranteed Compatibility - Western Digital performs extensive
   testing in its Functional Integrity Test Lab (FIT Lab) to
   ensure compatibility with all 100% AT-compatible computers and
   standard operating systems.

 - Reed Solomon ECC On-the-Fly - The Caviar implements Reed Solomon
   error correction techniques to obtain extremely low read error
   rates. This error correction algorithm corrects errors
   on-the-fly without any performance penalties. It allows for
   hardware corrections of up to a 72-bit error span on-the-fly.

 - Automatic Defect Retirement - If the Caviar drive detects a
   defective sector while writing, it automatically relocates the
   sector without enduser intervention.


 Defect Management
 -----------------
 Every Caviar undergoes factory-level intelligent burn in, which
 thoroughly tests for and maps out defective sectors on the media
 before the drive leaves the manufacturing facility. Following the
 factory tests, a primary defect list is created. The list contains
 the cylinder, head, and sector numbers for all defects.

 Defects managed at the factory are sector slipped. Grown defects that
 can occur in the field are mapped out by relocation to spare sectors
 on the inner cylinders of the drive.


 Format Characteristics
 ----------------------
 The Caviar is shipped from the factory preformatted (low-level) with
 all the known defects mapped out. In order to be compatible with
 existing industry standard defect management utility programs, the
 Caviar supports the logical format command. When the host issues the
 Format Track command, the Caviar performs a logical version of this
 command in response to the host's interleave table request for good
 and bad sector marking or assign/unassign the sector to/from an
 alternate sector.

 If the host issues the Format Track Command during normal operating
 modes, the data fields of the specified track are filled with a data
 pattern of all zeros. The Format Track Command can be used to
 mark/unmark bad sectors, and reassign unrelocated sectors.


 Automatic Defect Retirement
 ---------------------------
 The automatic defect retirement feature automatically maps out
 defective sectors while writing. If a defective sector appears,
 Caviar finds a spare sector.


 Error Recovery Process
 ----------------------
 The Caviar has four means of error recovery:

 - ECC On-the-Fly

 - Preamp Thermal Asperity (TA) compensation

 - Read/Write Retry Procedure

 - Extended Read Retry Procedure

 - Extended (Firmware Assisted) ECC Correction and Realocation


 ECC On-the-Fly - If an ECC error occurs, the Caviar attempts to
 correct it on-the-fly without retries. Data can be corrected in this
 manner without performance penalty.


 Preamp Thermal Asperity Compensation - A Thermal Asperity (TA) is a
 baseline shift in the readback signal due to heating of the magneto-
 resitive stripe on the head as a result of physical contact with the
 disk or a particle.

 The preamp circuit has the ability to detect and compensate for
 thermal asperities. When an error cannot be corrected by ECC
 On-the-Fly, another retry is performed, where the preamp with its
 thermal asperity detection feature determines if the error is due to
 a thermal asperity. Once the preamp determines that the error is due
 to thermal asperity, preamp compensation is enabled. If preamp
 compensation alone is not enough to recover, then the channel
 performs a series of TA-specific recoveries.


 Read/Write Retry Procedure - This retry procedure is used by all disk
 controller error types. If this procedure succeeds in reading or
 writing the sector being tried, then recovery is complete and the
 controller continues with the command. Each retry operation also
 checks for servo errors. This procedure ends when error recovery is
 achieved or when all possible retries have been attempted.


 Extended Read Retry Procedure - This retry procedure tries
 combinations of positive/negative track offsets, and data DAC
 manipulations to recover the data. This retry procedure is applicable
 only to read data recovery. The Read/Write Retry procedure is used
 to perform the actual retry operation.

 When an extended retry operation has been successful, the controller
 continues with the command. The controller ensures that any changes
 in track offset or data DAC settings that exist are cleared before
 the command continues.


 Extended (Firmware Assisted) ECC - If an ECC error is too large to
 correct using ECC on-the-fly, the Caviar can attempt to correct the
 error using Extended Error Correction. This allows correction of
 large ECC errors that ECC on-the-fly cannot correct. However, the
 Extended Error Correction process takes more time than ECC
 on-the-fly to return the corrected data.


 REED SOLOMON ECC On-the-Fly
 ---------------------------
 The WD Caviar implements Reed Solomon error correction techniques in
 hardware to reduce the uncorrectable read error rate. This allows a
 high degree of data integrity with no impact on the drive's
 performance. Because on-the-fly corrected errors do not require the
 drive's firmware to assist with error correction, they are invisible
 to the host system.

 To obtain the ECC check byte values, each byte within the sector is
 interleaved into one of three groups, where the first byte is in
 interleave 1, the second byte is in interleave 2, the third byte is
 in interleave 3, the fourth byte is in interleave 1, and so on.

 Interleaving and the ECC formulas enable the drive to detect where
 the error occurs. A maximum of one byte can be corrected in each
 interleave without firmware assistance.


 Firmware Assisted ECC
 ----------------------
 With firmware assisted ECC, a maximum of 3 random bytes can be
 corrected in each interleave. In this case, a 113-bit single-burst
 error span is the maximum that is always correctable with firmware
 assistance because the entire error span will never occupy more than
 three bytes in each interleave.


 Universal Address Translation
 -----------------------------
 The Caviar implements linear address translation. The translation
 mode and translated drive configuration are selected by using the Set
 Drive Parameters command to issue head and sector/track counts to the
 translator. Caviar supports universal translation. Therefore, any
 valid combination of cylinder, head, and SPT can be assigned to the
 drive as long as the total number of sectors is not greater than the
 physical limits. The product of the cylinder, head and sectors/track
 counts must be equal to or less than the maximum number of sectors
 available to the user.

 AC12100   -  4,124,736
 AC23200   -  6,346,368
 AC24300   -  8,421,840
 AC35100   - 10,568,880
 AC36400   - 12,594,960

 Each sector consists of 512 bytes.

 The values in the Sector Count Register and the SDH Register
 determine the Sectors Per Track (SPT) and heads. Regardless of the
 values of the SPT and the heads, Caviar is always in the translation
 mode.


 Power Conservation
 ------------------
 The AC12100/23200/24300/35100/36400 support the ATA-4 power
 management commands that lower the average power consumption of the
 disk drives.

 For example, to take advantage of the lower power consumption modes
 of the drive, an energy efficient host system could implement a power
 management scheme that issues a Standby Immediate command when a
 host resident disk inactivity timer has expired. The Standby
 Immediate command would cause the drive to spin down and enter a
 low-power mode. Subsequent disk access commands would cause the drive
 to spin up and execute the new command.

 To avoid excessive wear on the drive due to the starting and stopping
 of the HDA, the host's disk inactivity timer should be set to no
 shorter than ten minutes.


 High-Speed DMA Capability
 -------------------------
 By engaging an ATA-4 compatible, Mode 2 multi-word DMA, the host CPU
 bandwidth is increased because the peripheral data transfer burden is
 off-loaded to the system's DMA channel. With the exception of DMA
 data transfers, which are limited to Read DMA and Write DMA
 commands, all other commands must be performed using PIO. DMA or PIO
 data transfer mode selection by the host is performed on a
 command-by-command basis.


 Ultra DMA/33
 ------------
 The AC12100/23200/24300/35100/36400 support high-speed Ultra Direct
 Memory Access 33 (Ultra DMA/33) host transfers. Mode 2 Ultra DMA/33
 doubles the current burst DMA transfer rate of 16.67 MB/s to 33.3
 MB/s. Mode 2 Ultra DMA/33 increases throughput by utilizing hardware
 for time-consuming interface control functions during host-to-disk
 and disk-to-host transfers. This allows disk functions to execute in
 the background thus freeing up the system to perform other tasts.


 Advanced Host Transfers
 -----------------------
 The AC12100/23200/24300/35100/36400 support high-speed Mode 3 and 4
 PIO.

 These are data transfer modes that utilize hardware handshaking
 between the host and the drive via the IORDY signal. When the drive
 deasserts the IORDY signal, the host extends the read/write cycle
 until IORDY is asserted, thereby eliminating data corruption from
 overrun and underrun conditions. When in Mode 3 PIO, data can be
 transferred in bursts to and from the host at a rate of up to 11.1 MB
 per second; in Mode 4 PIO, the data can be transferred at a rate of
 up to 16.6 MB per second.

 Mode 3 and Mode 4 PIO are enabled on the drive by issuing a Set
 Features command. If Mode 3 or Mode 4 PIO is enabled, it can only be
 disabled by issuing another Set Features command, a hard reset, or by
 cycling power.

 To support Mode 4 PIO, Flow Control must be enabled in the host
 system. If this mode is enabled on a system that does not support
 Flow Control, host FIFO errors can occur.

 Mode 3 and Mode 4 PIO timings were defined to facilitate EIDE drive
 integration into VL and PCI local bus systems.


 Zoned Recording
 ---------------
 Zoned Recording is a mechanism for increasing the capacity of the
 drive by increasing the Bit-Per-Inch (BPI) density of data written
 on the longer outer tracks of the drive. Track capacity (number of
 sectors) is constant within groups of tracks or zones, and is
 increased when the tracks are sufficiently long to accommodate a
 significant number of additional sectors. This incremental increase
 in track capacity moving outward on the disk surface creates a series
 of concentric zones with different data densities.


 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.

 These WD Caviar drives monitor read error rate, start/stop count,
 spin-up retry count, drive calibration retry count, G-list entry
 count, and multi-zone error rate.

 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.


 WESTERN DIGITAL Defect Management Utility
 -----------------------------------------
 All Caviar EIDE drives are defect-free and low level formatted at the
 factory. After prolonged use, any drive, including Caviar, may
 develop defects. If you continue receiving data errors in any given
 file at the DOS level, you can use the defect management utility
 WDDIAG.EXE to recover, relocate and rewrite the user data to the
 nearest spare sector and maintain a secondary defect list.

 Caution: As with all format utilities, some options in the WDDIAG.EXE
 utility will overwrite user data.


 Dual Drive Option
 -----------------
 WD Caviar drives support ATA-4 dual drive operations by means of
 configuratin options for master or slave designation.

 The WD Caviar is 100% ATA-4 compatible regarding the timing of the
 PDIAG- and DASP- signals. A jumper must be placed in the drive's
 option area for both master and slave configurations. If a jumper is
 placed in the drive's option area for both master and slave
 configurations. If a jumper is placed on the cable select (CSEL)
 option, the drive address selection will be determined by the CSEL
 signal on the drive cable. Connection to the host is implemented by
 means of a daisy-chain cable assembly.

 The SDH Register contains the master/slave select bit for the Caviar.
 The DASP- signal is a time-multiplexed indicator of Drive Active or
 Slave Present on the Caviar's I/O interface. At reset, this signal is
 an output from the slave drive and an input to the master drive,
 showing that a slave drive is present. For all times other than
 reset, DASP- is asserted at the beginning command processing and
 released upon completion of the comand. If the master drive option
 has been configured, the WD Caviar will not respond to commands or
 drive option has been configured, the WD Caviar will not respond to
 commands or drive status on the interface when the slave bit is
 selected in the SDH Register.



**********************************************************************
                      G   E   N   E   R   A   L
**********************************************************************
WESTERN   AC35100/36400

 Introduction
 ------------
 Ultra DMA is a high-speed data transfer feature that allows DMA
 commands to transfer data at 33.3 MB/s - double the current burst DMA
 transfer rate of 16.6 MB/s while using the standard 40-pin IDE
 interface cable.

 Ultra DMA lets host computers send and retrieve data faster, removing
 the bottlenecks associated with data transfers - especially during
 sequential operations. Western Digital's WD Caviar hard drives
 that support Ultra DMA are able to transmit and receive data at
 higher rates resulting in greater performance.

 In addition to speed improvements, Ultra DMA delivers new data
 integrity capabilities to the EIDE interface. Improved timing margins
 and the use of Cyclical Redundancy Check (CRC), a data transfer error
 detection code, help to ensure the integrity of transferred data.

 Ultra DMA is also recognized as Ultra ATA and Fast ATA-2 and is
 endorsed by the industry's leading hard drive manufacturers,
 including Fujitsu, IBM, Maxtor, Quantum, Seagate, Toshiba, Western
 Digital, and others.


 More Ultra DMA Information
 --------------------------
 1. Ultra DMA hard drives are backward compatible with existing
    EIDE/IDE hard drives, CD-ROM drives and host systems.
    Examples: 1) an Ultra DMA hard drive can be installed in a
                 system that supports EIDE or IDE;
              2) the latest motherboards that support Ultra DMA also
                 support standard EIDE interfaces.

 2. Ultra DMA supported hard drives and standard EIDE/IDE hard drives
    can be used in the same system.


 VIA Chipset
 -----------
 There is a known issue involving a small shipment of Western Digital
 high-performance WD Caviar Ultra DMA hard drives and the VIA VPX and
 VP2/97 (also marketed as AMD-640) chipsets.

 During the initiation phase of an Ultra DMA read data transfer, a
 series of commands are issued by the hard drive, the BIOS, and the
 VIA chipset. A deviation from standard protocol by the VIA VPX
 and VP2/97 chipsets is causing the system and the hard drive to go
 out of synchronization, resulting in a system that does not respond
 or locks up.


 Hard Drives Affected
 --------------------
 The specific Western Digital hard drives affected have CCC:C1
 firmware, were shipped between 9/10/97 and 10/8/97, with model
 numbers AC35100 and AC36400.


 Solution
 --------
 If using an Ultra DMA hard drive in a system with one of the VIA
 chipsets specified above, you must disable Ultra DMA. A hard drive
 firmware workaround solution has been developed to accommodate
 systems using the VIA chipsets specified above. Current shipments of
 Western Digital hard drives are not affected by this VIA chipset
 issue.


