
P R O D R I V E   4 2 5   S    QUANTUM
NO MORE PRODUCED                                      Native|  Translation
                                                      ------+-----+-----+-----
Form                 3.5"/HH               Cylinders    1520|     |     |
Capacity form/unform   426/      MB        Heads           9|     |     |
Seek time   / track  14.0/ 4.0 ms          Sector/track     |     |     |
Controller           SCSI2 SINGLE-ENDED    Precompensation
Cache/Buffer           256 KB SEGMENTED    Landing Zone
Data transfer rate    1.530 MB/S int       Bytes/Sector      512
                     10.000 MB/S ext SYNC
Recording method     RLL 1/7                        operating  | non-operating
                                                  -------------+--------------
Supply voltage     5/12 V       Temperature *C         4 55    |    -40 60
Power: sleep              W     Humidity     %         8 85    |      5 95
       standby            W     Altitude    km    -0.061  3.048| -0.061 12.192
       idle          11.5 W     Shock        g        10       |     60
       seek          12.8 W     Rotation   RPM      3606
       read/write         W     Acoustic   dBA        45
       spin-up            W     ECC        Bit   48,WITH 11BIT BURST COR
                                MTBF         h     150000
                                Warranty Month        24
Lift/Lock/Park     YES          Certificates     CSA,FCC,SDA,TUV,UL1950,VDE


**********************************************************************
                        L   A   Y   O   U   T
**********************************************************************
QUANTUM  PRODRIVE 425S  PRODUCT MANUAL 81100377-01, FEBRUARY 1992

  +----------------------------------------------------------+
  |                                         A2 A1 A0         |
  |                              JP1 +-+-+-++-+-+-+    RP12++|XX
  |                                  +-+-+-++-+-+-+        |||XX
  |                                  SS EP WS              |||XX
  |                                                        ++|XX
  |                                                    RP11++|XX SCSI
  |                                             Terminators|||XX J2
  |                                                        |||.X
  |                                                        ++|XX
  |                                                    RP10++|XX
  |                                                        |||XX
  |                                                        |||XX
  |                                                        ++|XX
  |                                                          |XX
  |                                                          |  1
 ++                                                          |XX
 ++ LED                                                      |XX J3
  +----------------------------------------------------------+  1



**********************************************************************
                      J   U   M   P   E   R   S
**********************************************************************
QUANTUM  PRODRIVE 425S  PRODUCT MANUAL 81100377-01, FEBRUARY 1992

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

 x = Jumper set at factory


 Jumper Options
 --------------
  +---------+-----------+-------------------------------------------+
  | Jumper  | Setting   | Description                               |
  +---------+-----------+-------------------------------------------+
  |   SS    | OPEN   x  | Self-seek test disabled                   |
  |         | CLOSED    | Self-seek test enabled                    |
  +---------+-----------+-------------------------------------------+
  |   EP    | CLOSED x  | Parity checking enabled                   |
  |         | OPEN      | Parity checking disabled                  |
  +---------+-----------+-------------------------------------------+
  |   WS    | OPEN   x  | Wait/Spin disabled                        |
  |         | CLOSED    | Wait/Spin enabled                         |
  +---------+-----------+-------------------------------------------+
  |   A2    | CLOSED x  | A0, A1, and A2 are used in combination to |
  |   A1    | CLOSED x  | determine the drive's SCSI ID. The default|
  |   A0    | OPEN   x  | value is six.                             |
  +---------+-----------+-------------------------------------------+


 SS  Self-Seek Jumper
 --------------------
 Quantum ships the ProDrive 425S hard disk drive from the factory
 with no Self-Seek (SS) jumper installed- that is, with the self-seek
 test disabled. To enable the Self-Seek test, install a the SS jumper.


 When the SS jumper is installed, the drive initiates a self-seek
 test. During the self-seek test, the drive can execute any command
 that does not require a disk access. When the self-seek test begins,
 the drive-activity LED (Light-Emitting Diode) lights and remains on
 as long as the test proceeds without error. The drive executes seeks
 in butterfly pattern. Each butterfly seek pattern starts and ends
 with a seek to cylinder 256, where the drive verifies the sector ID.
 If the vertification detects a seek error, the self-seek test
 terminates immediately and the LED flashes continously until the SS
 jumper is removed. When the SS jumper is removed, the drive completes
 the seek pattern in progress and turns off the LED. The drive
 attempts no error recovery and is ready to execute any command.


 EP  Enable Parity Jumper
 ------------------------
 The Enable Parity (EP) jumper controls parity checking across the
 SCSI bus. Installing the EP jumper enables parity checking. Quantum
 ships ProDrive 425S hard disk drive from the factory with the
 EP jumper installed. Removing the EP jumper disables parity checking.
 The drive still generates parity, but does not perform parity check-
 ing. When the jumper is changed, the new setting takes effect at the
 next power on.


 WS  Wait/Spin Jumper
 --------------------
 The Wait/Spin (WS) jumper controls the Wait/Spin option. Quantum
 ships the ProDrive 425S hard disk drive from the factory with
 no WS jumper installed - that is, with the Wait/spin option disabled.
 With the Wait/Spin option disabled at power-on, the motor starts
 spinning automatically and the drive is ready within 20 seconds. To
 enable Wait/Spin option, install the WS jumper.

 With the WS jumper installed at power-on, the motor does not start to
 spin until the host sends a START/STOP UNIT command. This delay
 permits power sequencing, preventing the system power supply from be-
 ing overloaded by simultaneous demands for peak start current from
 multiple devices. Once the drive receives the START/STOP UNIT
 command, it is ready within 20 seconds.


 A2/A1/A0  SCSI-Bus Device Identification
 ----------------------------------------
 The SCSI bus can support up to eight devices, including the host
 system. The identification number of each device determines its
 priority level. Prior to installing the ProDrive 425S hard disk
 drive, you must choose its SCSI-device identification number.

 Jumpers installed across three pair of jumper pins - A2, A1 and A0 -
 in various combinations permit the assignment of the drive's
 identification number. These three pairs of jumper together comprise
 a 3-bit binary number, in which A2 is the most-significant bit and A0
 is the least significant bit. With a jumper installed, a pair of pins
 represents a 1; with no jumper installed a 0. Thus, with jumpers
 installed across all of the pins, the device identification is 7;
 without jumpers installed, the device identification is 0.

 Quantum ships the ProDrive 425S hard disk drive from the factory
 with the A2 and A1 jumpers installed - that is, the drive's default
 SCSI-device identification is 6. If the jumpers are changed, the new
 device identification takes effect at the next power on.

   +----------+-----------------------+
   | SCSI ID  |        Jumpers        |
   |          |  A2   |  A1   |  A0   |
   +----------+-------+-------+-------+
   |    0     | OPEN  | OPEN  | OPEN  |
   |    1     | OPEN  | OPEN  | CLOSED|
   |    2     | OPEN  | CLOSED| OPEN  |
   |    3     | OPEN  | CLOSED| CLOSED|
   |    4     | CLOSED| OPEN  | OPEN  |
   |    5     | CLOSED| OPEN  | CLOSED|
   |x   6     | CLOSED| CLOSED| OPEN  |
   |    7     | CLOSED| CLOSED| CLOSED|
   +----------+-------+-------+-------+

 The SCSI bus supports up to eigth devices, including the host system.
 A device's identification number determines its priority and must be
 unique in the system.


 Driver Terminators
 ------------------
 On the ProDrive 425S hard disk drive, three resistor networks
 installed in sockets on the PCB terminate the SCSI bus. Quantum ships
 the ProDrive 425S hard disk drive from the factory with the
 terminating resistors installed. On a SCSI bus, only the first device
 - usually the host - and the last device can contain terminating
 resistors. When installing the ProDrive 425S hard disk drive
 in any other position on the bus, remove the terminating resistors.
 When using the ProDrive 425S with a differential SCSI Adapter Kit
 where the TERM PWR line is used to provide power to external
 terminating resistors, remove the termination resistors from the hard
 disk drive, and add an i-line termination resistor pack between the
 differential SCSI adapter kit 50 pin SCSI connector and the 50-pin
 connector on the SCSI flat cable.



**********************************************************************
                      I   N   S   T   A   L   L
**********************************************************************
QUANTUM  PRODRIVE 425S  PRODUCT MANUAL 81100377-01, FEBRUARY 1992

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

 Orientation
 The ProDrive 425S can be mounted in ANY orientation.
 #6-32 UNC screws are recommended for mounting.

 Note
 With the exception of the faceplate and integral mounting bracket,
 clearance between the drive and any other surface must be a minimum
 of 0.10 inch.

 CAUTION: The PCB is very close to the mounting holes. Do not exceed
 the specified length for the mounting screws. The specified screw
 length allows full use of the mounting-hole threads, while avoiding
 damaging or placing unwanted stress on the PCB. To avoid stripping
 the mounting-hole threads, the maximum torque applied to the screws
 must not exceed 8 inch-pounds.


 Ventilation
 -----------
 The ProDrive 425S hard disk drive operates without a cooling
 fan, provided the ambient air temperature does not exceed 131*F
 (55*C). Any user-designed cabinet should provide adequate air
 circulation to prevent the maximum temperature from being exceeded.


 J3 DC Power Connector
 ---------------------
 The DC power connector (J3) is a 4-pin Ranoda Molex connector 8981-
 4SM3 or equivalent, mounted on the back edge of the Printed-Circuit
 Board (PCB).
   +----------+
   |4  3  2  1|
   +----------+

 Recommended connectors and their numbers:

 4-pin connector:         AMP P/N 1-480424-0 or equivalent

 Loose-piece contacts:    AMP P/N 60619-4 or equivalent

 Strip contacts:          AMP P/N 61117-4 or equivalent

  pin 1    +12 VDC
  pin 2    +12 Volts Return (Ground)
  pin 3    + 5 Volts Return (Ground)
  pin 4    + 5 VDC

 Note:
 Pins 2 and 3 are connected on the drive.


 J2  SCSI Connector
 ------------------
 The SCSI cable connector (J2) on the ProDrive 425S hard disk drive
 is a 50-pin universal header.

 Note:
 A key slot on the header prevents the incorrect installation of the
 header connector on the SCSI cable. To prevent the header connector
 on the SCSI cable from being plugged in backwards, use only a keyed
 header connector.

 Recommended header connectors and their part numbers:

 50-pin connector (without strain relief) AMP P/N 1-746195-2 or
 equivalent

 50-pin connector (with strain relief) AMP P/N 1-499508-2 or
 equivalent


 LED Operation
 -------------
 Whenever the drive initiates the execution of a command, a green LED
 on the faceplate lights, and remains lit until the execution of the
 command is complete, disconnectec, or aborted.


 Air Filtration
 --------------
 ProDrive Series hard disk drives are Winchster-type drives. The heads
 fly very close to the media surface, with a nominal flying height of
 6 microinches. Therefore, it is essential that the air circulating
 within the drive be kept free of paticles. Quantum assembles the
 drive in a Class-100, purified air environment, then seals the drive
 with a metal cover. When the drive is in use, the rotation of the
 disks forces the air inside the drive through an internal filter.


 SCSI Electrical Characteristics
 -------------------------------
 All signals are asserted, or true, at the low level, and use open-
 collector drivers terminated at each end of the cable with 220 ohms
 to +5 volts (nominal) and 330 ohms to ground. On the ProDrive 425S
 hard disk drive, resistor networks in sockets terminate the lines.

 Note
 To connect multiple devices on a SCSI bus, remove the terminating
 resistors on all but the two devices at the cable ends.

 Each signal driven by the ProDrive 425S hard disk drive has
 the following output characteristics:

 - True (signal assertion) = 0.0 to 0.5 volts DC at 48 milliamperes
                             (maximum)

 - False (signal deassertion) = 2.5 to 5.25 volts DC

 Each signal from the host to the ProDrive 425S hard disk
 drive must have the following characteristics, as measured at the
 drive:

 - True (signal assertion) = 0.0 to 0.8 volts DC

 - False (signal deassertion) = 2.5 to 5.25 volts DC

 The ProDrive 425S hard disk drive uses a standard 50-pin SCSI-bus
 connector (J2) - providing a single-ended, non shielded connection.
 The maximum cable length is 20 ft (6 meters). Odd pins are grounded
 with the exception of Pin 25, which is not connected.

 --------------------------------------------------------------------

 DIFFERENTIAL SCSI ADAPTER KIT
 -----------------------------
 The adapter kit consists of a printed-circuit board (PCB) assembly
 with flex circuit, a plastic connector protector, and retainer clip.
                                            +-+------+
                                      8-pin |x|      |
                                      Header+-+--+   |Flex Cable
                                                 |   |
                                                 |   |
                                              +--+   |
                                              |   +--+
                                              |   |
                +-----------------------------+---+
 Drive    +----+|XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXDrive SCSI Connector
 Power    |XXXX||XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX |
 Connector++++++|+-------------------------------+|
           |||| ||::::::::::::::::*::::::::::::::||Differential SCSI
        +--++++-++-------------------------------+|Connector
        | xxx+|                                   |
        | xxx-+    DIFFERENTIAL PCB               |
        |                                         |
        | XXXXXX System Power Connector           |
        +-----------------------------------------+

 Precautions
 -----------
 The installation of the differential SCSI adapter kit is simple and
 straightforward. However, before installation you should be aware of
 the following precautions.

 1. Static Electricity. The integrated circuits used on the
    differential adapter and the disk drive are sensitive to static
    electricity. Just prior to handling the adapter board, be sure to
    discharge the static electricity from your body by wearing a
    properly grounded wrist strap or touching a grounded object (a
    metal water pipe, bare metal part of the system chasis or the
    adapter's disk drive housing). Failure to take this precaution,
    may damage the drive or the adapter PCB circuitry.

 2. Flex Cable Damage. The adapter board comes with a flex cable. The
    flex cable is used to connect the adapter kit to the drive. It
    should be handled gently.

 3. Disk Drive Damage. Disk drives should be handled with care. Be
    careful to not subject the drive unnecessary shock or roughness.
    This will ensure that you do not cause damage to the drive or its
    data.

 4. Compatibility. Only the following Quantum drives and adapters
    should be used together:

                     Drive       Adapter Kit
                   ProDrive 425S   D_425


 Adapter PCB Installation
 ------------------------
 Push the adapter SCSI connector into the mating connector on the
 drive. Next, push the 4-pin power connector of the adapter into the
 mating connector on the drive.


 Removal fo Terminating Resistors
 --------------------------------
 Remove resistor packs RP10, RP11, RP12.


 Flex Cable Installation
 -----------------------
  ------------------------------------------------------+
                     8-pin                              |
   CONNECT FLEX CABLE****      JP1+-+-++-+-+-+        ++|XX
   HERE!             ****       +-+-+-++-+-+-+        |||XX
                                                      |||XX

 A flex cable connects the differential SCSI adapter to the PCB. The
 free end of the flex cable contains an 8-pin female header. Secure
 the flex cable to the underside of the PCB by gently bending the
 cable and aligning the four guide holes in the cable with the four
 outer pins of RP12, then push the cable so that the pins go through
 the holes snugly. This can be accomplished by using a pair of
 tweezers or similar tool. Plug the header at the end of the flex
 cable should be facing upwards (the flex cable side goes onto the
 header pin first). In order to keep the flex cable routed properly,
 use the pressure-sensitive adhesive strips attached to the flex
 cable. (Before attaching the flex cable to the drive remove the
 protective covering on the pressure-sensitive adhesive strips.)
 Secure the flex cable to the tops of the two large ICs (U21, U10).


 Connector Protector and Retainer Clip Attachment
 ------------------------------------------------
 With the adapter board securely connected to the drive, and with the
 flex cable installed, cover the soldered ends of the upper two rows
 of connector pins on the adapter PCB with the plastic protector
 (groove side facing out). Next, attach the retainer clip (it holds
 the protector securely to the adapter PCB). To do this, first hook
 the left end of the clip into the 50-pin connector. Then, holding the
 clip near the right end with needle-nose pliers, "wrap" the clip
 around the connector protector and hook the right end of the clip
 into the end of the connector.


 Drive Cable Connection
 ----------------------
 The system differential SCSI cable and power cables can now be
 connected. Insert them into the appropriate connectors on the
 adapter.

 This complete the installation. The drive is now ready to receive
 power and to operate as a differential SCSI device.


 Differential Adapter Board
 --------------------------
 The differential SCSI adapter board consists of a small PCB that
 translates all SCSI-bus signals coming from the drive single-ended to
 differential, and translates signals to the drive from differential
 to single-ended.

 The adapter board contains two 50-pin connectors. The single-ended
 female SCSI connector (P1) mates to the matching 50-pin connector on
 the drive. The differential male SCSI connector (J2) provides for
 connection to a differential host system.

 System power is relayed to the drive by means of two 4-pin power
 connectors. P3 is a 4-pin female connector that attaches to the
 power connector on the drive, and J3 is a 4-pin male connector that
 receives power from the system.

 A flexible cable connects 5 proprietary control and 3 drive ID lines
 from the PCB on the main drive to the differential adapter board
 through connector P6.


 Cable Requirements
 ------------------
 Ordinary 50-pin flat cable (non-twisted pair) is not recommended for
 use in a differential SCSI system due to excessive crosstalk at very
 short distances. Either twisted-pair flat cable or 25 twisted-pair
 regular cable (non-flat) having the following characteristics is
 recommended:

  Characteristic impedance:         90 to 132 ohms
  Signal attenuation:               0.095 dB maximum per meter @ 5 MHz
  Pair to pair propagation delta:   0.20 ns maximum per meter
  DC resistance:                    0.230 ohms maximum per meter
  Total cable length:               25 meters maximum
  Stub length:                      0.2 meters maximum

 Mixing cable types on the same SCSI bus - such as twisted-flat to
 twisted-round twisted-flat - is specifically discouraged due to the
 resultant impedance discontinuities and signal reflections.


 Difference Fron Single-Ended Operation
 --------------------------------------
 The differential signals found in the operation of the differential
 SCSI adapter differ from normal single-ended SCSI signals. The
 signals in a differential SCSI-bus can assume three different states
 - true, false, and released. A signal is false when +SIGNAL is
 asserted (high) and -SIGNAL is deasserted (low). A signal is false
 when +SIGNAL is deasserted (low) and -SIGNAL is asserted (high). A
 signal is released when both +SIGNAL and -SIGNAL are neither
 asserted nor deasserted (tri-state).

 Also, in a differential SCSI-bus, there are no "OR-tied" signals, as
 there are in a single-ended SCSI bus. Furthermore, under no
 circumstances may a device drive any signal to a state other than
 that to which it is already being driven by another device.

 NOTE
 Going from single-ended to differential causes no degradation in data
 transfer rates.


 Interface Characteristics
 -------------------------
 All active signals on the differential SCSI interface consist of two
 lines designated +SIGNAL and -SIGNAL, where SIGNAL is the name of a
 particular line. A signal is true when +SIGNAL is a minimum of 200
 millivolts more positive than -SIGNAL. A signal is false when -SIGNAL
 is a minimum of 200 millivolts more positive than +SIGNAL. All
 signals should be terminated at the end of the cable with a 150 ohm
 resistor between +SIGNAL and -SIGNAL, a 330 ohm resistor between
 -SIGNAL and +5V (TERMPWR), and a 330 ohm resistor between +SIGNAL and
 ground.

 The differential adapter board has no provision for internal
 termination. The DIFFSENS signal on the connector is used solely for
 the purpose of automatically disabling the differential drivers
 should a single-ended cable be inadvertently connected to the differ-
 ential adapter board.

 Each pair of differential signals driven by the adapter board has the
 following characteristics:

     Signal assertion:     0 to 1.7 VDC @ 55 mA (maximum)
     Signal deassertion:   2.7 to 5.25 VDC @ 55 mA (maximum)
     Differential voltage: 1.0 VDC (min.) with a common mode voltage
                           range of -7 to +12 VDC

 Also, all outputs conform to the EIA RS-485-1983.1 standard for
 balanced digital multipoint communication.


 Each pair of differential signals driven by the host system must have
 the following characteristics:

     Signal assertion:     0 to 1.7 VDC
     Signal deassertion:   2.7 to 5.25 VDC
     Differential voltage: 1.0 VDC (min.) with a common mode voltage
                           range of -7 to +12 VDC



**********************************************************************
                      F   E   A   T   U   R   E  S
**********************************************************************
QUANTUM  PRODRIVE 425S  PRODUCT MANUAL 81100377-01, FEBRUARY 1992

 General Description
 -------------------
 The Quantum ProDrive Series is a broad family of high-performance,
 3 1/2-inch form factor hard drives manufactured to meet the highest
 product-quality standards. These drives use nonremovable rigid disks
 as their storage media, have formatted capacities that range from
 40 to 426 megabytes, and are available with various interfaces.


 Indroduction
 ------------
 The ProDrive 425S intelligent hard disk drive features the Small
 Computer System Interface 2 (SCSI-2) and use powerful SCSI commands
 to optimize system performance. Because the drives manage defects and
 error recovery internally, these operations are fully transparent to
 the user.

 NOTE
 As defined by Quantum a megabyte is 1,000,000 bytes.


 Reliability
 -----------
 Mean Time Between Failures (MTBF): 150,000 Power On Hours (POH),

 Preventive Maintenance (PM):       Not required

 Mean Time To Repair (MTTR):        30 minutes

 Start/Stop:                        10,000 cycles (minimum)


 Seek Times/Miscellaneous Times:
 ------------------------------

 Times                  | Typical   | Nominal   | Maximum    |
 msec.                  | Nominal   | Condition | Worst-Case |
                        | Condition |           | Condition  |
 -----------------------+-----------+-----------+------------+
 Single Track Seek      |    4      |     5     |     5      |
 Average Seek           |    14     |     15.5  |     16.5   |
   Read-on Arrival      |    13     |     14.5  |     15.5   |
 Third-Stroke Seek      |    15     |     16.5  |     17.5   |
 Full-Stroke Seek       |    27     |     30    |     33     |
 Average Rotational     |           |           |            |
 Latency                |    8.3    |     ---   |     ---    |
 Sequential Head Switch |    4      |     ---   |     ---    |
 Power-Up Time          |    20     |     20    |     20     |
 -----------------------+-----------+-----------+------------+

 Seek time is the time required for the actuator to seek and settle on
 track. Quoted seek times include head settling time, but not command
 overhead or rotational latency time.

 Seek time is measured by averaging 1000 seeks of the indicated
 length. Average seek time is the average time of 1000 random seeks.
 When a seek error occurs, recovery for that seek may take up to two
 seconds.


 Media Quality
 -------------
 The ProDrive 425S hard disk drive features automatic defect
 management, making the manual identification of defects unneccessary.
 Defect management is completely transparent to the user.


 Track Format
 ------------

    Zone     |User Sec./Cyl.    MB/Sec.
 ------------+-------------------------
 Inner      7|  394             1.53
            6|  439             1.70
            5|  484             1.87
            4|  529             2.05
            3|  574             2.22
            2|  610             2.36
            1|  655             2.53
 Outer      0|  700             2.71


 Error Rates
 -----------
 A data error occurs whenever the drive fails to read or write a
 sector of data correctly. An error detected when reading may be
 correctable or uncorrectable. When a data error occurs, if the data
 can be transferred successfully using the drive's default error-
 recovery algorithm, the data error is recoverable; otherwise, it is
 unrecoverable. The miscorrection rate indicate the frequency with
 which the drive transfers incorrect read data, due to faulty ECC
 correction using the default error-recovery algoritm.

 If a data error recurs on each of eight retries, it is a read error;
 otherwise it is a soft error. Hard errors generally occur due to
 media defects.


 Defect Detection
 ----------------
 At sector level, any discrepancy between recorded data and recovered
 data constitutes a data error. In high-density digital recording
 systems, it is necessary to use an error-detection and correction
 scheme to enhance the performance and increase the reliability of the
 system.

 Data errors are either soft - correctable on retries and not readily
 repeatable - or hard - repeatable with high probability. The
 signal-to-noise ratio of the system affects the occurrence of soft
 errors, which represent marginal conditions of the media, heads,
 read/write circuitry. Hard errors occur due to defects, pits,
 scratches, or thin spots in the media. The drive can detect and skip
 defective sectors on the media. Thus, the drive will not use
 defective sectors for storage.


 Factory-Found Defects
 ---------------------
 At the factory, Quantum scan the disks for defective sectors and
 deallocates sectors containing defects prior to shipment. The drive
 records a primary defect list that contains the locations of all
 factory-found defective sectors in a reserved cylinder on the disk.
 The defects are spared in-line. In-line sparing skips each factory-
 found defects and shifts subsequent sectors on the track to
 sequential sectors. Two sectors at the end of each cylinder are
 spares, or replacement sectors. The drive allocates spare sectors as
 required to maintain the proper number of blocks per cylinder.


 Acoustics
 ---------
 Idle Mode:   45 dBA maximum, at 1 foot in any direction


 Power Sequencing
 ----------------
 If power is applied or removed during drive operation, no data will
 be lost or damaged, with the powwible exception that data may be lost
 in the sector being written at the time of the power loss. During
 power-up or power-down, the drive can sustain transient voltages be-
 tween +10% and -100% of the nominal voltage, and can sustain the
 shorting out or opening up to either voltage or return line.


 Power Reset Limit
 -----------------
 The following power resets limits are measured at the drive power
 connector:

           +5V   4.65 V
          +12V  10.50 V

 While powering up, the drive remains reset, or inactive, until the
 voltages applied exceed both power reset limits. The drive becomes
 reset when either supply voltage drops below the lower threshold. The
 minimum hysteresis is 50 mV.


 Automatic Actuator Lock
 -----------------------
 To ensure data integrity and prevent damage during shipment, all
 ProDrive Series hard disk drives feature a dedicated landing zone and
 Quantum's patented AIRLOCK. AIRLOCK, locks the headstack in the
 landing zone. It consists of an airvane mounted near the perimeter of
 the disk stack and a locking arm that restrains the actuator arm
 assembly when the disks are not rotating.

 When DC power is applied to the motor and the disk stack rotates, the
 rotation generates an airflow on the surface of the disk. As the flow
 of air across the airvane increases with disk ratation, the locking
 arm pivots away from the actuator arm, enabling the headstack to move
 out of the landing zone. When DC power is removed from the motor, a
 return mechanism automatically pulls the actuator into the landing
 zone, where the AIRLOCK holds it in place.


 DisCache
 --------
 Quantum's proprietary, look-ahead, caching scheme - provides faster
 access to data on the disk by anticipating host-system requests for
 data. DisCache prefetches data into a three segment cache in high-
 speed RAM (Random-Access Memory). When the host requests data pre-
 fetched to the cache, the drive accesses the cache, rather than the
 disk. The ProDrive 425S hard disk drive uses an advanced continuous-
 prefetch algorithm. When the drive receives a READ command that re-
 quests data currently in the cache, it continues to prefetch data.
 The 64 kilobyte segment containing the oldest data is the segment
 that gets updated with new read data.


