
H P   9 7 5 5 8   E    HEWLETT PACKARD
NO MORE PRODUCED                                      Native|  Translation
                                                      ------+-----+-----+-----
Form                 5.25"/FH              Cylinders    1962|     |     |
Capacity form/unform  1084/      MB        Heads          15|     |     |
Seek time   / track  13.5/ 3.0 ms          Sector/track   72|     |     |
Controller           ESDI                  Precompensation
Cache/Buffer               KB              Landing Zone
Data transfer rate    2.875 MB/S int       Bytes/Sector      512
                            MB/S ext
Recording method     RLL 2/7                        operating  | non-operating
                                                  -------------+--------------
Supply voltage     5/12 V       Temperature *C           50    |    -40 70
Power: sleep              W     Humidity     %         8 80    |      5 80
       standby            W     Altitude    km    -0.061  3.048| -0.300 15.240
       idle               W     Shock        g         6       |     30
       seek          33.0 W     Rotation   RPM      4002
       read/write    26.0 W     Acoustic   dBA        40
       spin-up            W     ECC        Bit   64
                                MTBF         h     150000
                                Warranty Month
Lift/Lock/Park     YES          Certificates     CSA,IEC950,TUV,UL1950,VDE    

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                        L   A   Y   O   U   T
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HEWLETT  HP 97556/58/60E  PRODUCT DESCRIPTION MANUAL 5960-0116, 8.91

  +---------------------------------------------------------+
  |                                  8-------1  4-----1     |XX
  |                                  +-------+S1+-----+S2   |XXData
  |                                                         |XX
  |                                                         |
  |                                                         |XX
  |                                                         |XX
  |                                                         |XX
  |                                                  +-+    |XX
  |                                       Termination| |    |XXControl
  |                                       Resistor   | |    |XX
  |                                       Pack       +-+    |XX
  |                                                         |XX
  |                                                         |+-+Sync
  |                                                         ||x|Spind.
  |                                                         |+-+
 ++LED                                                      |XX
 ++                                                         |XX Power
  +---------------------------------------------------------+



**********************************************************************
                      J   U   M   P   E   R   S
**********************************************************************
HEWLETT  HP 97556/58/60E  PRODUCT DESCRIPTION MANUAL 5960-0116, 8.91

 Jumper Setting
 ==============

                                                        Sync
    ESDI                  ESDI                       Spindle
    Data Connector        Control Connector          Pins
    +-----------++--+     +------------------++--+  +xxxxx--+-----+--+
    |           ||  |     |                  ||  |  |xXXXX  |XXXXX|  |
   ++           ++  +-----+                  ++  +--+xxxxx  +-----1  |
   |                              Termination                Power   |
   |1+--+-+                       Resistor Pack                      |
   |2|S2|-+Sector Size            +---------+                        |
   |3|  |-+                       +---------+                        |
   |4+--+Byte Sync ECC                                               |
   |1+--+Auto-Align-+                                                |
   |2|S1|Offline----+- Automatic                                     |
   |3|  |All Heads--+  Head Alignment                                |
   |4|  |Extended Direct Head Addressing                             |
   |5|  |Spin-up At Power On                                         |
   |6|  |-+
   |7|  | +-ESDI Address
   |8+--+-+
   |


 END VIEW
 --------

 |                                                               |
 |                                        Sync Spindle  Power    |
 |   ESDI Data       ESDI Control         Pins        +-------+  |
 |+--XXXXXXXXXXXXXX--XXXXXXXXXXXXXXXXXXXX--2-4--------+O O O O+-+|
 ||                                        o o o o o  +4-3-2-1+ ||
 ||                                        o o o o o            ||
 |++                                       1 3 +-+-+           ++|
 +-+                                           Not Used        +-+


 DC Power and pin connector assignments
 --------------------------------------
 Pin 1    +12 VDC +5%
 Pin 2    +12 Volts Return
 Pin 3    + 5 Volts Return
 Pin 4    + 5 VDC +5%


 Synchronized Spindle Pins
 -------------------------
 Pin 1    Ground
 Pin 2    Slave Sync
 Pin 3    N/C (Key)
 Pin 4    Master Sync

 There are four configurations of the synchronized spindle function:
 Stand Alone, Slave, Master, and Master Control. The HP 97556/58/60
 ESDI Disk Drives supports all four.

 The power-on default for all drives disables is the Stand Alone mode.
 In this mode, the drive does not transmit or receive any sync
 signals.

 When the drive is in the Stand Alone mode:

  - It does not transmit a sync signal on the master line.
  - It does not receive an externally sourced slave sync input.

 When the drive is set to the Slave mode:

  - It does not transmit a sync signal on the master line.
  - It receives and syncs to an externally sourced slave sync on the
    slave input line.

 When the drive is set to the Master mode:

  - It transmits a sync signal on both the master and slave lines.
  - It syncs internally to the same signal

 When the drive is set to the Master Control mode:

  - It transmits a sync signal on the master line.
  - It receives and syncs to an externally sourced sync on the slave
    line.



 S1 Head Alignment Control
 -------------------------

 +-------+--------------------------+--------------------------------+
 |Drive  |Switch Status             | Drive Action                   |
 |State  +------+---------+---------+                                |
 |       |S1-1  |S1-2     |S1-3     |                                |
 |       |(Auto-|(Off-    |(All-    |                                |
 |       |Align)|line)    |Heads)   |                                |
 +-------+------+---------+---------+--------------------------------+
 |Automatic Mode                                                     |
 +-------+------+---------+---------+--------------------------------+
 |Needed:|      |         |         |                                |
 |       |ON    |No Effect|OFF      |Embed an alignment of the       |
 |       |      |         |         |current head in next Seek       |
 |       |      |         |         |                                |
 |       |ON    |No Effect|ON       |Embed an alignment of All-Heads |
 |       |      |         |         |in next Seek                    |
 +-------+------+---------+---------+--------------------------------+
 |Criti- |      |         |         |                                |
 |cal:   |      |         |         |                                |
 |       |ON    |OFF      |OFF      |Write Protect Media             |
 |       |      |         |         |Embed an alignment of the       |
 |       |      |         |         |current head in next Seek       |
 |       |      |         |         |                                |
 |       |      |         |ON       |Write Protect Media             |
 |       |      |         |         |Align All-Heads on next         |
 |       |      |         |         |Recalibrate, or Reset Attention |
 |       |      |         |         |                                |
 |       |ON    |ON       |No Effect|Write Protect Media             |
 |       |      |         |         |Immediately disconnect and      |
 |       |      |         |         |execute All-Heads alignment.    |
 |       |      |         |         |NOTE: this operation may        |
 |       |      |         |         |interrupt an in-progress Read or|
 |       |      |         |         |Write                           |
 +-------+------+---------+---------+--------------------------------+
 |Host-Controlled Mode                                               |
 +-------+------+---------+---------+--------------------------------+
 |Needed:|      |         |         |                                |
 |       |OFF   |No Effect|No Effect|Wait 1 minute for Seek          |
 |       |      |         |         |Declare Seek Fault              |
 |       |      |         |         |Embed current head alignment in |
 |       |      |         |         |next Seek, OR                   |
 |       |      |         |         |embed All-Heads alignment in    |
 |       |      |         |         |next Recalibrate or Reset       |
 |       |      |         |         |Attention                       |
 +-------+------+---------+---------+--------------------------------+
 |Criti- |      |         |         |                                |
 |cal:   |      |         |         |                                |
 |       |OFF   |No Effect|No Effect|Declare Seek Fault              |
 |       |      |         |         |Write protect media             |
 |       |      |         |         |Embed current head alignment in |
 |       |      |         |         |next Seek, OR                   |
 |       |      |         |         |embed All-Heads alignment in    |
 |       |      |         |         |next Recalibrate, or Reset      |
 |       |      |         |         |Attention                       |
 +-------+------+---------+---------+--------------------------------+

 The drive executes a complete calibration and head alignment for all
 heads during the Power-On sequence. For subsequent operation, there
 are two modes for head alignments: the automatic mode, or the
 Initiator-controlled mode. In the automatic (default) mode, the drive
 automatically embeds head alignments in Seek commands. In the Host-
 controlled mode, head alignments are executed upon receipt of a
 Recalibrate command.


 Head Alignment States
 ---------------------
 The drive will enter a head alignment needed or critical state
 according to changes in temperature since the last alignment, or the
 elapsed time since the last head alignment.

 +------------------------------+------------------------------------+
 |Temperature Considerations    |    Elapsed Time Considerations     |
 +------------------------------+------------------------------------+
 |If a temperature increase     | Under normal conditions, the drive |
 |exceeds the first two pre-    | schedules head alignment calibra-  |
 |defined (at the factory)      | tions at preset intervals since    |
 |thresholds, the drive enters  | spin-up. The drive enters the      |
 |the head alignment needed     | needed state at these intervals. If|
 |state. If a head alignment    | a head alignment occurs, the drive |
 |occurs the drive cancels the  | cancels the needed state. If enough|
 |the needed state. If the      | time passes without calibration    |
 |temperature increase exceeds  | that a Write operation may be un-  |
 |the second (higher) threshold | reliable, the drive enters the     |
 |before a head alignment is    | critical state. The time periods   |
 |acomplished, the drive enters | between head alignments are pre-   |
 |the critical state.           | defined at the factory to assure   |
 |                              | reliable operation under start-up  |
 |                              | and long term conditions.          |
 +------------------------------+------------------------------------+

 Typical Head Alignment Times
 ----------------------------
 The time requirements for head alignments will vary according to how
 they are executed.

 Some typical values are listed below:

     Single Head Alignments:           127 milliseconds

     All-Heads Alignment:

      - 11 data heads                  847 milliseconds
      - 15 data heads                 1135 milliseconds
      - 19 data heads                 1423 milliseconds


 S1 Extended Direct Head Addressing
 ----------------------------------
 S1-4  OFF  Use Drive Select 3 as Drive Select 3
       ON   Use Drive Select 3 as Head Select 4

 This option converts the Drive Select Bit 3 line (pin 30) of the
 ESDI Control connector to a fifth head select line providing faster
 host access to data heads 16, 17, and 18 of the HP 96560E Disk
 Drives. In this configuration, only three drives can be supported on
 the ESDI interface.


 Valid Head Select Values
 ------------------------
  +-----------+--------------------+--------------------------+
  |Head       |  Standard Head     |  Data Head Selected      |
  |Select 4(1)|  Select Lines      |                          |
  +-----------+--------------------+--------+--------+--------+
  |   2(4)    | 2(3) 2(2) 2(1) 2(0)| 97556E | 97558E | 97560E |
  +-----------+--------------------+--------+--------+--------+
  |                      Head Group Zero(2)                   |
  +-----------+-----+----+----+----+--------+--------+--------+
  |   0       |  0  | 0  | 0  | 0  |    0   |    0   |    0   |
  |   0       |  0  | 0  | 0  | 1  |    1   |    1   |    1   |
  |   0       |  0  | 0  | 1  | 0  |    2   |    2   |    2   |
  |   0       |  0  | 0  | 1  | 1  |    3   |    3   |    3   |
  |   0       |  0  | 1  | 0  | 0  |    4   |    4   |    4   |
  |   0       |  0  | 1  | 0  | 1  |    5   |    5   |    5   |
  |   0       |  0  | 1  | 1  | 0  |    6   |    6   |    6   |
  |   0       |  0  | 1  | 1  | 1  |    7   |    7   |    7   |
  |   0       |  1  | 0  | 0  | 0  |    8   |    8   |    8   |
  |   0       |  1  | 0  | 0  | 1  |    9   |    9   |    9   |
  |   0       |  1  | 0  | 1  | 0  |   10   |   10   |   10   |
  |   0       |  1  | 0  | 1  | 1  | Invalid|   11   |   11   |
  |   0       |  1  | 1  | 0  | 0  | Invalid|   12   |   12   |
  |   0       |  1  | 1  | 0  | 1  | Invalid|   13   |   13   |
  |   0       |  1  | 1  | 1  | 0  | Invalid|   14   |   14   |
  |   0       |  1  | 1  | 1  | 1  | Invalid| Invalid|   15   |
  +-----------+--------------------+--------+--------+--------+
  |                      Head Group One(2)                    |
  +-----------+-----+----+----+----+--------+--------+--------+
  |   1       |  0  | 0  | 0  | 0  | Invalid| Invalid|   16   |
  |   1       |  0  | 0  | 0  | 1  | Invalid| Invalid|   17   |
  |   1       |  0  | 0  | 1  | 0  | Invalid| Invalid|   18   |
  +-----------+-----+----+----+----+--------+--------+--------+
  |NOTES:                                                     |
  |                                                           |
  |1: The Drive Select Bit 3 (pin 30) of the ESDI Control     |
  |   Cable Connector is converted to Head Select 4 when      |
  |   Extebded Direct Head Addressing is enabled (S1-4 = ON). |
  |                                                           |
  |2: When Extended Direct Head Addressing is enabled, all    |
  |   heads are assigned to Head Group Zero (0), and the drive|
  |   will only accept an ESDI Select Head Group command to   |
  |   Head Group Zero (0). When Extented Direct Addressing is |
  |   disabled, the drive will accept an ESDI Select Head     |
  |   Group command to Head Group zero (0) or Head Group One  |
  |   (1).                                                    |
  +-----------------------------------------------------------+


 S1 Automatic Spin-Up at Power-On
 --------------------------------
 S1-5  OFF  Automatic spin-up at power-on
       ON   Spinup on Host command

 When  S1-5 is set to the OFF position, the disk drive spins up
 automatically when power is applied. When set to the ON position, the
 disk drive will spin up only on command from the controller.


 S1 ESDI Address
 ---------------
   +----------+-----------------------+
   | ESDI     |                       |
   | Address  | S1-6  | S1-7  | S1-8  |
   +----------+-------+-------+-------+
   |    0     | OFF   | OFF   | OFF   |
   |    1     | OFF   | OFF   | ON    |
   |    2     | OFF   | ON    | OFF   |
   |    3     | OFF   | ON    | ON    |
   |    4     | ON    | OFF   | OFF   |
   |    5     | ON    | OFF   | ON    |
   |    6     | ON    | ON    | OFF   |
   |    7     | ON    | ON    | ON    |
   +----------+-------+-------+-------+

 If Extended Direct Head Addressing is enabled (S1-4 = ON), S1-6 has
 no effect, and addresses 4 through 7 are not available.


 S2  Sector Size/Byte Sync ECC Switch Selections
 -----------------------------------------------

   +------------------------------------------------------------+
   |                     Sector Size                            |
   +-----+------+-------+---------------------------------------+
   |S2-1 |S2-2  |S2-3   |  Bytes per Sector / Sectors per Track |
   |     |      |       |   Hex (DEC)       |  Hex (DEC)        |
   +-----+------+-------+-------------------+-------------------+
   |OFF  |OFF   |OFF    |   0256 (598)      |  0048 (72)        |
   |OFF  |OFF   |ON     |   010A (266)      |  00A2 (162)       |
   |OFF  |ON    |OFF    |   0145 (325)      |  0084 (132)       |
   |OFF  |ON    |ON     |   014F (335)      |  0080 (128)       |
   |ON   |OFF   |OFF    |   024E (590)      |  0049 (73)        |
   |ON   |OFF   |ON     |   0450 (1134)     |  0026 (38)        |
   |ON   |ON    |OFF    |   086B (2155)     |  0014 (20)        |
   |ON   |ON    |ON     |   10D6 (4310)     |  000A (10)        |
   +-----+------+-------+-------------------+-------------------+

 Sector Size Power-On Default
 ----------------------------
 Switch segments S2-1, S2-2, and S2-3 determine the Power-On default
 for the number of bytes (including the inter-sector gap) that can be
 formatted between the Sector/Index pulses. As sector size increases,
 the corresponding number of sectors per track decreases. The default
 sector size can be changed with the ESDI Set Bytes per Sector
 command.


 S2 Byte Sync ECC
 ----------------
 S2-4  OFF  Disable
       ON   Enable

 This option provides error correction for the sync patterns pre-
 ceeding the header address and data fields. The Byte Sync ECC option
 can correct most single-bit drop-in, drop-out, or bit shift errors.

 Byze Sync ECC is enabled when S2-4 is set to ON. When Byte Sync ECC
 is enabled, an 8-bit sync pattern of hexadecimal DC (1101 1100) must
 be used. In addition, when Byte Sync ECC is enabled, the error
 correction process extends the Read Propagation Delay time by nine
 bit times. This requires corresponding additions to the pad files.

 Byte Sync ECC is disabled when S2-4 is set to OFF. When Byte Sync ECC
 is disabled, the host may use any sync pattern.

 NOTE
 When Byte Sync ECC is enabled (S2-4 = ON), the Read Data interface
 signal clocked on the interface by the drive will be all zeros until
 a valid or correctable byte sync has been detected.


 Front Panel LED Indicator
 -------------------------
 The light emitting diaode (LED) indicator on the front of the disk
 drive displays the status of the power-on diagnostics. As the drive
 progresses through the diagnostics, the LED will display the
 following indications:

 1. ON   When the disk drive is switched on, the power-on reset line
         from the drive hardware illuminates the LED. The LED remains
         lit until extinguished by the microprocessor on the drive
         electronics/controller PCA. If the LED remains on, a failure
         has occured. The most probable cause is a failure of the
         drive electronics/controller PCA.

 2. OFF  Once the processor has performed Self Test, the LED goes off.
         The LED stays off for approximately 1 second, while the
         processor performs additional hardware tests and establishes
         various operating parameters. If the LED indication change to
         "quick flash" at an approximate 1 Hz rate, the most propable
         cause is a failure of the ESDI interface control circuitry on
         the drive electronics/controller PCA.

 3. ON   The LED goes again to indicate that the spindle motor is be-
         ing started. The LED stays on until the spindle is up to
         speed. If the drive is not configured to spin up at power-on,
         (S1-5 = ON), this step of the sequence will be skipped.

 4. FLASHING
         A "slow-blink" LED indication of approximately 1 Hz means
         that the drive is waiting for the controller to initiate
         channel activity. If the controller sends a command
         immediately, this LED pattern may not be seen. If the LED
         continues to "slow blink" at a rate of 1 Hz, the controller
         is not communicating with the drive. This may be caused by a
         hardware failure, a disconnected interface cable, or an
         incorrect ESDI address set on the disk drive.

 Once the controller establishes communication, the LED functions as
 an activity light. The LED reflects the state of the ESDI Drive
 Selected signal: when asserted, the LED is ON; when negated, the LED
 is OFF.



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                      I   N   S   T   A   L   L
**********************************************************************
HEWLETT  HP 97556/58/60E  PRODUCT DESCRIPTION MANUAL 5960-0116, 8.91

 Notes on installation
 =====================

 Protection From Mechanical Shock
 --------------------------------
 The mechanism is attached to th emounting frame(s) by pliable shock
 mounts that isolate it from mechanical shock when properly installed.
 Before installation, the disk drive is susceptible to damage from
 excessive shock and vibration during shipping and handling. Dropping
 a drive almost always causes immediate damage, but setting a drive
 down too hard may shorten its operational life. The damage can be
 hidden, and can reduce the life of the drive, or cause unexplained
 failure to occur at a later date.


 Physical Mounting
 -----------------
 There are eight (8) threaded mounting holes (for 6/32 threads) on the
 disk drive: two on each side, and four on the bottom. Typically, the
 disk drive is fastened directly to a chassis with 6/32 screws. Use
 the following guidelines to mount the disk drive:

  - Use 6/32 screws and torque them to 10 inch-pounds.

  - When mounted, the hardware must not protude more than 1 mm (0.04
    inch) beyond the inside of the disk drive frame.


 Airflow Requirements
 --------------------
 The disk drive must be installed such that the ambient air
 temperature surrounding the disk drive is maintained within the
 limits.

 Airflow is required to maintain disk drive performance and
 reliability. The disk drive can be cooled by forced air or by natural
 cooling. Forced air may be necessary if the disk drive is located
 within a cabinet or other enclosure. If forced air cooling is not
 used, the disk drive must be located such that internal heat is
 conducted away from the drive and no outside heat sources raise the
 operating temperatures above the limits.


 Frame Ground Connector
 ----------------------
 The frame ground connector provides a ground contact to the drive
 casting.


 Terminator Resistor Pack
 ------------------------
 The drive is shipped with a 14-pin DIP terminator resistor pack
 installed. The pack is located on the bottom of the electronics/
 controller PCA. When installing multiple drives on an ESDI interface,
 the pack must be removed from all but the last drive in the chain.


 Cable Requirements
 ------------------
 The disk drive adheres to the cabling requirements and limitations
 of the ANSI ESDI specifications.

  - 34-conductor and 20-conductor flat cables should be used. Cable
    length should be less than or equal than 3.0 metres.

  - To minimize discontinuities and signal reflections, do not use
    cables with different impedances on the same bus.

  - A minimum cable size of 28 AWG should be used to minimize noise
    effects.

  - Cables should be properly terminated.


 Recommended Mating Connectors
 -----------------------------
 ESDI Control Connector               3M 3463-0041

 ESDI Data Connector                  3M 3461-0041

 DC Power                             AMP 1-480424-0

 Frame Ground                         AMP 62187-1

 Synchronized Spindle Pins Connector  AMP Housing 1-86427-0 (*1)

 *1 Also requires a contact set; (For 20-24 gauge wire, use AMP
    1-85969-6)


 Power Distribution
 ------------------
 The +5 and +12 voltages provided by an external dc power supply are
 distributed to the spindle motor driver, actuator driver, analog
 amplifiers, and digital circuitry. A reset output alerts the other
 circuits when power-on occurs and when power is lost. Each circuit
 responds in a predefined manner to the reset conditions.



**********************************************************************
                      F   E   A   T   U   R   E  S
**********************************************************************
HEWLETT  HP 97556/58/60E  PRODUCT DESCRIPTION MANUAL 5960-0116, 8.91


 Product Description
 -------------------
 The HP 97556/58/60, Option 050, Disk Drives are reliable, high
 capacity, high performance, random access mass storage devices
 utilizing sputtered thin-film 5.25-inch disks as storage media. The
 electrical interface of the Option 050 drives is compatible with the
 industry standard Enhanced Small Device Interface (ESDI).

 These drives incorporate a hybrid servo design that provides the
 flexibility and performance of a dedicated servo system and the
 dynamic head alignment of an embedded servo system.



 Seek Time
 ---------
       +-----------------------------------+--------+
       |Track-to-Track          msec. typ. |   3    |
       +-----------------------------------+--------+
       |Random Average          msec. typ. |  13.5  |
       +-----------------------------------+--------+
       |Maximum Seek (1962 cyl) msec. typ. |  25    |
       +-----------------------------------+--------+
       |Incremental Head Switch msec. typ. |   0.8  |
       +-----------------------------------+--------+
       |Latency (Average)       msec. avg. |   7.5  |
       +-----------------------------------+--------+


 Assembly Descriptions
 ---------------------
 The assemblies in the disk drive include the head/disk assembly (HDA)
 and the drive/electronics printed-circuit assemly (OCA). The sealed
 HDA contains the mechanical and electromechanical assemblies of the
 disk drive. The drive/electronics PCA provides all electronic control
 over the HDA.


 Head/Disk Assembly
 ------------------
 The head/disk assembly (HDA) contains disks, heads, an actuator
 assembly, head interface circuits, atmospheric controls, vibration
 isolators, and a spindle assembly. An aluminium casting provides the
 supporting structure for these parts. The entire assembly is sealed
 and is not field repairable.


 Disks
 -----
 The disks are 130 mm (5.1 inch) diameter aluminium substrate with a
 sputtered thin-film surface. The disks are mounted on the spindle
 assembly in stacks of six (97556E), eight (97558E), or ten (97560E)
 disks. Data is stored on all surfaces except for the bottom surface
 of the bottom disk, which is dedicated for servo use.


 Heads
 -----
 Eleven (97556E), fifteen (97558E), or nineteen (97560E) MIG data
 heads in the HDA write and read user data. An additional thin-film
 head is used to recover the servo information on the bottom surface
 of the bottom disk.


 Actuator Assembly
 -----------------
 Mechanical positioning of the read/write heads is achieved using a
 rotary actuator. Actuator current is supplied by the actuator driver,
 which amplifies position information from the servo circuits. A
 shipping latch captures the heads at the inside diameter of the disks
 (away from user data) whenever power is removed from the disk drive.
 This prevents the actuator from moving until power is applied to the
 disk drive. At power-on, the servo processor releases the latch,
 allowing normal movements of the heads.


 Atmospheric Controls
 --------------------
 The atmospheric controls in the HDA consist of a breather system and
 a recirculating filter. The breather system equalizes air pressure
 within the HDA to ambient air pressure. A breather filter prevents
 contaminants from entering the HDA. A recirculating filter maintains
 a low particle count within the HDA.


 Vibration Isolators
 -------------------
 To protect the HDA from random external vibrations, it is mounted on
 vibration isolators.


 Spindle Assembly
 ----------------
 The spindle assembly provides the mechanical mounting for the disks.
 The spindle rotates on a ball bearing system and is driven by an
 "in-hub" brushless DC motor. The 3-phase drive current for the motor
 is provided by the spindle drive circuit on the drive/electronics
 PCA. Three Hall-effect sensors, mounted on the spindle assembly,
 provide feedback signals to the spindle control electronics for
 coarse speed and phase switching control.


 Defect List Format
 ------------------
 A defect list implemented according to the ESDI specification is
 included on the disk media. Each defect entry is 5 bytes long. These
 five bytes define the physical location of a single media defect.
 Defect lists resides on the last cylinder, last cylinder minus eight,
 and at cylinder 4095.

 Maximum Defects               50 defects per surface, but not exceed:

 For  6 disks                  300 defects per drive
 For  8 disks                  400 defects per drive
 For 10 disks                  500 defects per drive


