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Hard Drive: IMPRIMIS: WREN VIFH 94191-766 676MB 5.25"/FH SCSI1 SE

W R E N   V I F H   9 4 1 9 1 - 7 6 6    IMPRIMIS
NO MORE PRODUCED                                      Native|  Translation
Form                 5.25"/FH              Cylinders    1632|     |     |
Capacity form/unform   676/  766 MB        Heads          15|     |     |
Seek time   / track  15.5/ 3.0 ms          Sector/track   54|     |     |
Controller           SCSI1 SINGLE-ENDED    Precompensation
Cache/Buffer            32 KB LOOK-AHEAD   Landing Zone
Data transfer rate    1.875 MB/S int       Bytes/Sector      512
                      4.700 MB/S ext SYNC
Recording method     RLL 2/7                        operating  | non-operating
Supply voltage     5/12 V       Temperature *C        10 50    |    -40 70
Power: sleep              W     Humidity     %         8 80    |      5 95
       standby            W     Altitude    km    -0.305  3.048| -0.305 12.210
       idle          21.0 W     Shock        g        10       |     32
       seek               W     Rotation   RPM      3597
       read/write         W     Acoustic   dBA
       spin-up            W     ECC        Bit   48,INTERNAL
                                MTBF         h     150000
                                Warranty Month        12
Lift/Lock/Park     YES          Certificates     CSA,FCC,IEC380,IEC435,UL47...


SEAGATE ST4766N (94191-766) PRODUCT MANUAL 77765353-L, DEC. 1991

  |                                                      || |Drive
  |                                                      || |Select/
  |                                                      |+-+Option
  |                                                  +1  |XX
  |                                                  ||  |XX SCSI
  |                                                  ++  |XX Interface
  |                                      Resistor    +1  |XX J3
  |                                      Terminator  ||  |XX
  |                                      Packs       ++  |XX
  |                                                  ++  |XX
  |                                                  ||  |XX
  |                                                  +1  |XX1
  |                                                      |
  |                                                      |XX Power
  |                                                      |XX
  +------------------------------------------------------+  1


SEAGATE ST4766N (94191-766) PRODUCT MANUAL 77765353-L, DEC. 1991

Jumper Setting

  J4  SCSI ID/Option Select Header
           |o  o  o  o  o  o  o  o  o|
           |1  o  o  o  o  o  o  o  o|
           TP TP  4  2  1 (2)(3)(6)(7)

      |            | 4  2  1  |
      +------------+----------+  Drive ID is binary coded jumper
      |SCSI ID = 0 | o  o  o  |  position (most significant bit on
      |            | o  o  o  |  left), i.e., jumper in position 1
      +------------+----------+  would be Drive ID 1, no jumpers means
      |SCSI ID = 1 | o  o  x  |  ID 0.
      |            | o  o  X  |
      |SCSI ID = 2 | o  x  o  |
      |            | o  X  o  |
      |SCSI ID = 3 | o  x  x  |
      |            | o  X  X  |
      |SCSI ID = 4 | x  o  o  |
      |            | X  o  o  |
      |SCSI ID = 5 | x  o  x  |
      |            | X  o  X  |
      |SCSI ID = 6 | x  x  o  |
      |            | X  X  o  |
      |SCSI ID = 7 | x  x  x  |
      |            | X  X  X  |

 (2)  CLOSED  Enables the Motor Start Option. In this mode of
              operation the drive will wait for a Start Unit Command
              from the Host before starting the Motor.
      OPEN    see Note (6) below for description of delayed motor
              start feature.

 (3)  CLOSED  Parity checking by the WREN 6 is enabled.
              The use of parity is a system option. The WREN 6 SCSI
              will always generate parity detection.

 (4)  If the unit is not be terminated, remove terminator resistor
      module SIPs (DIPs). TP Jumper in left vertical position means
      terminator power (+5V) is from WREN 6 power connector. Jumper
      in horizontal position means terminator power is taken from
      interface cable. If the drive is not terminated, the TP jumper
      need not be installed.

 (6)  Jumper on enables delayed motor start (Motor Start jumper (2)
      must be off). Motor start up is delayed 16 times drive ID number
      in seconds; i.e., Drive 0 starts immediately, Drive 1 starts 16
      seconds later, Drive 2 starts 16 seconds after Drive 1, etc.

(7) Reserved Jumper Position

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

Note: Pins on the drive select and configuration select header are
provided to facilitate manual drive configuration. No devices other
than jumpers should be connected to these pins. Improper connection
to external devices (switches, connectors, etc.) could adversely
affect drive performance. Exact location of these pins and headers
may change without notice.


SEAGATE ST4766N (94191-766) PRODUCT MANUAL 77765353-L, DEC. 1991

Notes on installation

Drive mounting

     horizontally             vertically
   +-----------------+   +--+             +--+ +------------------+
   |                 |   |  +-----+ +-----+  | |                  | x
   |                 |   |  |     | |     |  | x+----------------+x
 +-+-----------------+-+ |  |     | |     |  | ||x              x||
 +---------------------+ |  |     | |     |  | ||  x          x  ||
                         |  |     | |     |  | ||    x      x    ||
      x           x      |  |     | |     |  | ||      x  x      ||
 +------x------x-------+ |  +-----+ +-----+  | ||       xx       ||
 +-+------x--x-------+-+ +--+             +--+ ||     x    x     ||
   |       xx        |                         ||   x        x   ||
   |     x    x      |                         || x            x ||
   +---x--------x----+                         |x                x|
     x            x                           x++----------------++x

Drive Orientation
The balanced rotary arm actuator design of the Wren 6 allows it to
be mounted in any orientation. All drive performance characterization
however, has been done with the drive in horizontal (disc level) and
vertical (drive on its side) orientations, and these are the two
preferred mounting orientations.

WREN 6 is designed, manufactured, and tested with a "Plug-in and
Play" installation philosophy. This minimizes the requirements for
highly trained personnel to integrate the WREN 6 into an OEM's
system, whetherin a factory or field environment.

Mounting Holes
Mounting Holes (6-32 UNC). Four on bottom, two on each side. Max.
screw length into chassis is 0.14 in. (3.55 mm).

Cabinet cooling must be designed by the customer so that the ambient
temperature immediately surrounding the WREN 6 will not exceed
temperature conditions. Specific consideration should be given to
make sure adequate air circulation is present around the PWAs at the
rear of the drive.

Service Tools
No special tools are required for site installation or recommended
site maintenance. The depot repair philiosophy of WREN 6 precludes
the necessity for special tools. If field repair of items external to
the HDA is desired, a 6 point Torx T10 driver is required. This may
be purchased through most commercial tool catalogs.

Physical Description
Model 94191 WREN 6 may be daisychained together or with other
compatible SCSI devices using a common cable. Both ends of the cable
must be terminated. The WREN 6 implements single ended or
differential drivers and receivers. Drives having single ended
interface drivers and receivers allow a maximum cable length of six
metres (primarily for connection within a cabinet). The Model
94191-766D WREN 6 implements differential drivers and receivers which
allow a maximum cable length of 25 metres. All signals are common
between all SCSI devices. The Model 94191 WREN 6 may be daisychained
only with SCSI devices having the same type drivers and receivers.
Devices having single ended interface circuits cannot be on the same
daisychain with devices having differential interface circuits. A
maximum of 8 SCSI devices (including the Host) may be daisychained
together. The SCSI Devices at both ends of the daisychain are to
terminated. Intermediate SCSI devices shall not be terminated. Remove
the terminator resistor packs, not the terminator power source
selector jumper.

Cable Requirements
Only nonshielded cable connectors are applicable. A 50 conductor flat
cable or 25 twisted pair cable shall be used. The maximum total cable
length shall be 6.0 metres for single ended drivers and receivers,
and 25.0 metres for differential drivers and receivers. A stub length
of no more than 0.1 metre for single ended or 2.0 metre for
differential circuits is allowed off the mainline interconnection
within any connected equipment. For single ended drivers and
receivers, an ideal impedance match with cable terminators implies a
cable characteristic impedance of 132 ohm single ended option and
122 ohms for the differential option. In general, cables having
characteristics impedance of those values are not available; however,
impedances that are somewhat lower are satisfactory. A characteristic
impedance of 100 ohm 10% is recommended for unshielded flat or
twisted pair ribbon cable. However, most available cables have a
somewhat lower characteristic impedance. To minimize discontinuities
and signal reflections, cables of different impedances should not be
used in the same bus. Implementations may require trade-offs in
shielding effectiveness, cable length, the number of loads, transfer
rates, and cost to achieve satisfactory system operation. If shielded
and unshielded cables are mixed within the same SCSI bus, the effect
of impedance mismatch must be carefully considered.

A minimum conductor size of 28 AWG should be used to minimize noise

Suggested nonshielded flat cable part numbers are:

    Flat cable     3M-3365-50
    Twisted pair   Spectra twist in flat 455-248-50

Equivalent parts may be used.

Connector Requirements
The nonshielded cable connector shall be a 50 conductor connector
constisting of to rows of 25 female contacts with adjacent contacts
100 mils apart.

Recommended Mating Flat Cable Connector Part Numbers are:

Closed end 3M-3425-7000 W/O Strain Relief, No Center Key
(for cable 3M-3425-7050 With Strain Relief, No Center Key
ends) Dupont-66900-290 With Strain Relief, With Center Key

Open end 3M-3425-6000 W/O Strain Relief, No Center Key
(In Daisy- 3M-3425-6050 With Strain Relief, No Center Key
chain) Dupont-66900-250 With Strain Relief, With Center Key

The Model 94191 WREN 6 device connector is a nonshielded 50
conductor connector consisting of two row of 25 male pins with
adjacent pins 100 mils apart. The connector is keyed.

Drive Connector Part Number: Berg - 65496 - 031 or equivalent.

Single Ended
All odd pins except pin 25 are connected to ground. Pin 25 is left

Pin 25 must not be connected to ground at the HOST end or the drive
end of the cable. If the I/O connector should accidentally be
plugged in upside down, terminator power on Pin 26 will shorted to

    |       +--+ HOST ADAPTER/INITIATOR ***    |
    |       |T |                               |
             |                1 thru 8 SCSI devices
             +--------- -----+--------------+
           **|             **|              |*
    +--------+---+ +---------+--+ +--------++-++
    |WREN        | |WREN        | |WREN    | T||
    |or other    | |or other    | |or other+--+|
    |SCSI device | |SCSI device | |SCSI device |
    +------------+ +------------+ +------------+

 *    Closed end type connector used
 **   Open type (in-line application) Connector used.
 ***  Host need not be on the end of the daisy chain. Another device
      can be on the end with the terminator, the host having no

T indicates termination required.

DC Cable and Connector
The WREN 6 receives DC power through a 4 pin right angle connector
mounted on the servo PWA. Recommended part numbers of the mating
connector are listed below, but equivalent parts may be used.

Type of cable: 14 AWG
Connector: AMP 1-480424-0
Contacts: AMP 60619-4 (Loose Piece); AMP 61117-4 (Strip)

 Electrical Description
 The Model 94191-766 WREN 6 uses single ended interface signals and
 these signals must be terminated with 220 ohm to +5 V and 330 ohm
 to ground at each end of the total cable. All signals use open
 collector or three state drivers. Optional termination is available
 internal to the WREN 6.

 The Model 94191-766D uses differential interface signals and each of
 these must be terminated at each end of the total cable with 330 ohms
 to +5 V and 330 ohms to ground with 150 ohms between each
 differential pair. All signals use open collector, three state
 drivers. Drives are shipped with or without terminators, depending on

Single Ended Drivers/Receivers
Single ended drivers and receivers are used by the WREN 6.

Transmitter Characteristics
The WREN 6 uses an ANSI SCSI compatible open collector single ended
driver. This driver is capable of sinking a current of 48 mA with a
low level output voltage of 0.4 volt.

Receiver Characteristics
The WREN 6 uses a ANSI SCSI single ended receiver with hysteresis
gate or equivalent as a line receiver.

Differential Drivers/Receivers
Differential drivers and receivers are used by the Model 94191-766D

 Differential Signals
 All signals consist of two lines denoted +SIGNAL and -SIGNAL. A
 signal is true when +SIGNAL is more positive than -SIGNAL, and a
 signal is false when -SIGNAL is more positive than +SIGNAL. All
 assigned signals ahall be terminated at each end of the cable.

Output Characteristics
Each signal driven by the WREN 6 (Differential Interface) shall have
the following output characteristics when measured at the WREN 6 SCSI

Low-level output voltage* = 2.0V max. at low-level output current =
55 milliamps.

High-level output voltage* = 3.0V min. at high-level output current =
-55 milliamps.

 Differential voltage = 1.0V min. with common-mode voltages ranges
 from -7V dc to +12V dc.

*These voltages shall be measured between the output terminal and the
SCSI device's logic ground reference.

The output characteristics shall aditionally conform to EIA

Input Characteristics
Each signal received by the WREN 6 (Differential Interface) shall
have the following input characteristics when measured at the WREN 6
SCSI connector:

 Input current on either input = +2.0 milliamps maximum.

These characteristics include both receivers and passive drivers.

 This requirement shall be met with the input voltage varying between
 -7V dc and +12V dc, with power on or off, and with the hysteresis
 equaling 35 mv, minimum.

The input characteristics shall additionally conform to EIA

Terminator Requirements
Internal WREN 6 I/O termination consist of three resistor modules
which plug into sockets on the Main PWA. The WREN 6 may be ordered
with or without these termination resistors to facilitate a
particular application. All single initiator/single target (non-
daisychain) applications require that the Initiator and WREN 6 be
terminated. Daisychain applications require that only the unit at
each end of the daisychain be terminated. All other peripherals on
the chain should not be terminated.

Note: Remove terminator resistor packs where terminators are not
required. Removal of terminator power source selection jumper does
not disconnect the terminator resistor from the circuit. SIP's for
Single Ended Interface Drivers/Receivers; SIP's and DIP's for
Differential Interface Drivers/Receivers Option.

Terminator Power
The WREN 6 does not supply Terminator power for the SCSI bus. The
WREN 6 may be configured to accept terminator power via Pin 26 of the
SCSI bus or to provide terminator power for optional internal
termination resistors via the WREN 6 power connector.
SCSI devices providing termination power (TERMPWR) shall have the
following characteristics:

     V TERM = 4.0V to 5.25V
     800 mA min source drive capability
     1.0 A maximum


SEAGATE ST4766N (94191-766) PRODUCT MANUAL 77765353-L, DEC. 1991

General Description
The WREN 6 is a member of a family of low cost, high performance,
highly reliable, random access storage devices designed to meet the
needs of the OEM marketplace.

The WREN 6 has been developed as a system peripherals to the
highest standards of design and construction. The WREN 6 depends
upon its host equipment to provide adequate power and environment in
order to achieve optimum performance and compliance with applicable
industry and governmental regualations. Special attention must be
given in the areas of safety, power distribution, shielding, audible
noise control, and temperature regulation.

The WREN 6 is a UL Recognized component per UL 478 and a CSA
Certified component per CSA C22.2 No. 220-M1986. It also meets the
requirements of DIN IEC 380/VDE 0806/8.81 and EN 60950/1.1.88, DIN
IEC 435/VDE 0805/11.84 and EN 60950/09.87.

The WREN 6 as delivered, is designed for system integration before
use. It is supplied as a sub-assembly, as such, it is not directly
subject to Subpart J of Part 15 of the FCC Rules and Regulations nor
the Radio Interference Regulations of the Canadian Department of

The Head, Disc and Actuator Assembly chamber (HDA) is environmentally
sealed at the factory. Air is recirculated within the HDA through a
nonreplaceable filter to maintain a contamination free disc/actuator

The WREN 6 uses a dedicated landing zone at the innermost radius of
the media thus eliminating the possibility of destroying or degrading
data by landing in the data zone.

The WREN 6 incorporates an automatic shipping look which prevents
potential damage to the heads and disks caused by movements during
shipping and handling. The shipping lock is automatically disengaged
when power is applied to the drive.

The WREN 6 decodes Track 0 location from the dedicated servo
surface thereby eliminating mechanical transducer adjustments and
related reliability concerns.

The WREN 6 uses a high performance actuator assembly consisting of
a low inertia, balanced, patented, straight arm design which provides
excellent performance with minimum power dissipation.

Media Description
The media used on the WREN 6 has a diameter of approximately 5
inches (130 mm). The aluminum substrate is coated with a thin film
magnetic material, overcoated with a proprietary protective layer for
improved durability and environmental protection.

Defect and Error Management
WREN 6, as delivered, complies with this specification. The read
error rate and specified storage capacity are not dependent upon use
of defect management routines by the host (initiator).

Defect and error management in the SCSI system involves WREN 6
internal defect/error management and SCSI systems error considera-
tions (errors in communications between Initiator and WREN 6). Tools
for use in designing a defect/error management plan are briefly
outlined in this section, with references to other sections where
further details are given.

WREN 6 Internal Defects/Errors
Identified defects are recorded on the WREN 6 defects list tracks
(referred to as the primary or ETF defect list). It is recommended
that these known defects be reallocated during the initial WREN 6
format operation. The WREN 6 internal retries and data correction
by ECC should be enabled to recover data from additional flaws if
they occur. If data correction by ECC is required to recover data,
the host should immediately reallocate this sector by use of the
Reassign Blocks command. If the WREN 6 automatic retries and data
correction by ECC features are not used, defects are usually un-
recoverable and need to be reallocated as they are diacovered. For
reallocation of bad sectors, the number of spare sectors per track or
cylinder and the number of spare tracks per volume is programmable.
After formatting, defects can be automatically reallocated by the
WREN 6, or can be reallocated when the host sends the Reassign
Blocks Command.

Seek Time

                                          |  94191  |
        Track-to-Track         msec. typ. |    3    |
                               msec. max. |    4    |
                       Average msec. typ. |   15.5  |
                       Average msec. max. |   17.5  |
        Full Stroke            msec. typ. |   35    |
                               msec. max. |   40    |
        Latency                msec. avg. |    8.33 |
 Seek times does not include drive controller overhead.

Read Look-Ahead/Cache Control
The WREN 6 Model 94191 provides a Read Look-ahead buffering algorithm
which can in may cases enhance system performance. This feature may
be selected by issuing a Mode Select Command with the Enable/Disable
Cache bit set in the Cache Control page.

Power Sequencing
Power sequencing is not required for the WREN 6. The WREN 6 protects
against inadvertent writing during power up and down. Daisychain
operation requires that power be maintained on the terminated WREN 6
to ensure proper termination of the peripheral I/O cables.

Start/Stop Time
After DC power has been applied, the WREN 6 will become ready within
39 seconds if the Motor Start Option is disabled. During this time,
the drive will respond to the SCSI interface. Stop time will be less
than 30 seconds from removal of DC power.

If the Motor Start Option is enabled, the internal controller will
accept a Motor Start, Inquiry or Request Sense Command via the SCSI
interface 3 seconds after DC power has been applied. After the Motor
Start Command has been received the WREN 6 will become ready for
normal operations within 36 seconds. During this time the drive will
respond to the SCSI interface in accorance with the rules for Command

There is no power control switch on the drive.

The drive will meet all specifications over a 50*F to 122*F (10*C to
50*C) ambient temperature range with a maximum gradient of 36*F
(20*C) per hour. The enclosure for the drive should be designed such
that the temperatures at the locations are not exceeded. Air flow may
be needed to achieve these temperature values.

Air Cleanliness
The WREN 6 is designed to operate in a typical office environment
with minimal environmental control.

The following reliability specifications assume correct host/drive
operational interface, including all interface timings, power supply
voltages, and environmental requirements.

MTBF 150,000 hours
Service Life 5 years
Preventive Maintenance None required

Sectors per track
54 @ 512 bytes per sector
28 @ 1024 bytes per sector

Formatted Capacity
Formatted capacity achieved depends on the number of spare
reallocation sectors reserved and the number of bytes per sector. The
following table shows some typical formatted capacities achievable.

 |Spare Sectors or Cylinders|           Sector Size*            |
 |Reserved for reallocation |512 Bytes/Sector| 1024 Bytes/Sector|
 |No Spares                 |     676 MB     |      701 MB      |
 |One Spare Sector per track|                |                  |
 |and two spare Cyl/Unit**  |     663 MB     |      675 MB      |
 |Two Spare Cylinders/Unit**|     675 MB     |      701 MB      |

The standard OEM Model is as follows:

                             Formatted Data Block Size*  Unformatted
 Model 94191-766 (15 Heads)  1024 Byte   512 Byte
                              675 MB     663 MB             766 MB

 * User selectable at format time. The user may  modify the data block
   size before issuing a format command and obtain different formatted
   capacities than those listed. User available capacity will depend
   on spare reallocation scheme selected.

** Spare cylinders are on the inner tracks

Heat/Power Dissipation
Each single ended interface WREN 6 will dissipate no more than 27
watts (92 BTUs per hour) of DC power average under worst case operat-
ing conditions. Typical power dissipation under idle operating con-
ditions is less than 21 watts.

WREN 5 drives having the differential interface circuits will
dissipate no more than 30 watts (102.2 BTU's per hour) of DC power
average under worst case operating conditions. Typical power
dissipation under idle operating conditions is less than 23.1 watts.

Electromagnetic Susceptibility
As a component assembly, the WREN 6 is not required to meet any
susceptibility performance requirements. It is the responsibility of
the system integrator to perform those tests required to assure that
equipment operating in the same system as the WREN 6 does not
adversely affect the performance of the WREN 6.

Logical Unit Number (LUN)
The logical unit number (LUN) addresses one of up to eight physical
devices or virtual devices attached to a target. The only valid LUN
number for WREN 6 is Zero.

The LUN in the CDB is provided for systems that do not implement the
Identify Message. If an Identify message is sent to the WREN 6, the
WREN 6 will use the LUN number specified in this message. In this
case, the WREN 6 shall ignore the LUN specified within the command
descriptor block.

The WREN 6 will reject commands which select an invalid LUN (except
Request Sense and Inquiry) by requesting and accepting the command
bytes, then going to Status phase and sending Check Condition status.
Note that the LUN is sent in the LUN field of a CDB (if no Identify
message has been received for this selection) or by the LUN field
of an Identify message.

Request Sense commands selecting an invalid LUN will receive a Sense
Data block with the Illegal Request Sense Key and an Invalid LUN
Error Code. Inquiry commands will return Inquiry Data with the
Peripheral Device Type field set to Logical Unit Not Present (7FH).
Request Sense and Inquiry commands will not send Check Condition
status in response to an invalid LUN selection.

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