
S T 1 5 1 5 0 F C   B A R R A . - 4 F C    SEAGATE
                                                      Native|  Translation
                                                      ------+-----+-----+-----
Form                 3.5"/HH               Cylinders    3711|     |     |
Capacity form/unform  4294/ 5062 MB        Heads          21|     |     |
Seek time   / track   8.5/ 0.8 ms          Sector/track     |     |     |
Controller           FIBRE CHANNEL DUAL    Precompensation
Cache/Buffer          1024 KB MULTI-SEGMEN Landing Zone
Data transfer rate    6.000 MB/S int       Bytes/Sector      512
                    100.000 MB/S ext
Recording method     RLL 1/7                        operating  | non-operating
                                                  -------------+--------------
Supply voltage     5/12 V       Temperature *C         5 50    |    -40 70
Power: sleep              W     Humidity     %                 |
       standby            W     Altitude    km                 |
       idle          18.4 W     Shock        g                 |
       seek               W     Rotation   RPM      7200
       read/write         W     Acoustic   dBA
       spin-up            W     ECC        Bit
                                MTBF         h     800000
                                Warranty Month        60
Lift/Lock/Park     YES          Certificates     CSA,EN60950,FCC,IEC950,UL1...


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                        L   A   Y   O   U   T
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SEAGATE  ST15150FC  INSTALLATION GUIDE 83329070, REV. A 9/95






       +---------------------------------------------+
       |                                             |
       |                                             |
       |                                             |
       |         INTERFACE                           |
       |          +-----------------------+          |
       +----------+XXXXXXXXXXXXXXXXXXXXXXX+----------+
                  +-----------------------+
               40-PIN







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                      J   U   M   P   E   R   S
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SEAGATE  ST15150FC  INSTALLATION GUIDE 83329070 REV. A  9/95

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

  REAR VIEW

     40 pin I/O and DC Power Wall/bracket Connection
                   |  Female
             +-----|----------+     TOP (HDA)
   ----------+ ++++++++++++++ +-----------
             +-1------------20+     BOTTOM

 Notes on 40 pin I/O connector:
      +12V  =  pins  2, 3, 4, 21
      +5V   =  pins  19, 20, 40
      GND   =  pins  6, 22, 23, 26, 29, 32, 35

 Mating FC connector: AMP US p/n: 787317-1 straight-in, Male 40-pin


 FRONT VIEW
 ----------
 Reserved. Shipped with cover installed. Do not remove. Do not install
 jumpers!                         |
                                  |     ++---- RESERVED
                                  |     ||+--- Fault LED
                                  |     |||+-- Port B Bypass LED
                                  |     ||||+- Port A Bypass LED
                      TOP (HDA)  ++---+-++++1+
     ---PCB----------------------+::::|::::::+--------
                ++    BOTTOM     +-J6-++++---+
                ++                     |||+++
                |                      ||| +-- Ground
            LED +                      ||+---- Active LED
                                       |+----- Ground
                                       +------ Remote LED (pin-11 +5v)

 ST15150FC drives have two ports for connection to two independent
 loops. Both loops may be active, but only one of these ports may be
 receiving or originating data at any one time. Do not connect both
 ports to the same loop.


 Connecting remote LEDs
 ----------------------
 NOTE
 THE LYJX-0 BOARD DOES NOT HAVE THE J20 CONNECTOR!!

 You can connect remote LEDS using J20.

 Connect the anode (usually the longer LED connector) to the +5V pin,
 and the cathode to the appropriate LED output pin. For example, if
 you want to attach an LED which lights up when the drive is active
 (reading or writing), connect the LEDs anode connector to J20 pin 6
 and the cathode to J20 pin 3.


   +-------------------+------------------------------------------+
   |                   |                                          |
   |                   +---+                                      |
   |                   +---+                                      |
   |                   |                                          |
   |    +-----+J20     |                                          |
   |    |* * 1|        |                                          |
   |    |* * 2|        |                                          |
   |    +-----+        |                                          |
   +-------------------+------------------------------------------+

   +-----+J20
   |o o *|    Port A Bypass LED
   |o o o|
   +-----+
   +-----+J20
   |o o o|    Port B Bypass LED
   |o o *|
   +-----+
  +-----+J20
   |o * o|    Active LED
   |o o o|
   +-----+
   +-----+J20
   |o o o|    Fault LED
   |o * o|
   +-----+
   +-----+J20
   |* o o|   GROUND
   |o o o|
   +-----+
   +-----+J20
   |o o o|   +5 VOLT
   |* o o|
   +-----+



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                      I   N   S   T   A   L   L
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SEAGATE  ST15150FC  INSTALLATION GUIDE 83329070 REV. A  9/95

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


 Drive orientation
 -----------------
 The drive may be mounted in any orientation. All drive performance
 characterizations, however, have been done with the drive in
 horizontal (discs level) and vertical (drive on its side) orienta-
 tions, which are the two preferred mounting orientations.

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

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

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


 Installation
 ------------
 ST15150FC disc drive installation is a plug-and-play process. There
 are no jumpers, switches, or terminators on the drive which need to
 be set. Simply plug the drive into the host's 40-pin Fibre Channel
 backpanel connector (FC-SCA)-no cables are required.
 The FC-AL interface is used to select drive ID and all option
 configurations for devices on the loop.

 If multiple devices are on the same FC-AL and physical addresses
 are used, set the device selection IDs (SEL IDs) on the backpanel
 so that no two devices have the same selection ID. This is called
 the hard assigned arbitrated loop physical address (AL_PA). There
 are 125 AL_PAs available. If you set the AL-PA on the backpanel to
 any value other than 0, the device plugged into the backpanel's
 SCA connector inherits this AL_PA. In the event you don't success-
 fully assign unique hard addresses (and therefore have duplicate
 selection IDs assigned to two or more devices), the FC-AL generates
 a message indicating this condition. If you set the AL-PA on the
 backpanel to a value of 0, the system issues a unique soft-
 assigned physical address automatically.

 Loop initialization is the process used to verify or obtain an
 address. The loop initialization process is performed when power
 is applied to the drive, when a device is added or removed from the
 FC loop, or when a device times out attempting to win arbitration.

 - Set all option selections in the connector prior to applying
   power to the drive. If you change options after applying power
   to the drive, recycle the drive power to activate the new settings.

 - It is not necessary to low level format this drive. The drive is
   shipped from the factory low level formatted in 512-byte sectors.
   You need to reformat the drive only if you want to select a
   different sector size or if you select a different spare sector
   allocation scheme.


 Do not touch the connector pins or any components on the control
 board without observing static-discharge precautions. Always handle
 the drive by the frame only.

 Mount the drive to the host system's chassis using four 6-32UNC
 screws. Two mounting holes are in each side of the drive and there
 are four holes in the bottom of the drive.


 Cooling
 -------
 Cabinet cooling must be designed by the customer so that the ambient
 temperature immediately surrounding the drive will not exceed
 temperature conditions.


 Air flow
 --------
 The rack, cabinet, or drawer environment for the Barracuda 4FC drive
 must provide cooling of the electronics and head and disc assembly
 (HDA). You should confirm that adequate cooling is provided using
 the temperature measurement guidelines described below.

 The drive should be oriented, or air flow directed, so that the
 least amount of air flow resistance is created while providing air
 flow to the electronics and HDA. Also, the shortest possible path
 between the air inlet and exit should be chosen to minimize the
 travel length of air heated by the drive and other heat sources
 within the rack, cabinet, or drawer environment.

 The air flow patterns are created by one or more fans, either
 forcing or drawing air as shown in the illustrations. Other air
 flow patterns are acceptable as long as the temperature
 measurement guidelines are met.

 To confirm that the required cooling for the electronics and HDA
 is provided, place the drive in its final mechanical configuration,
 perform random write/read operations and, after the temperatures
 stabilize, measure the case temperature of the components listed
 below.


 Drive mounting
 --------------
 Mount the drive using the bottom or side mounting holes. If you
 mount the drive using the bottom holes, ensure that you do not
 physically distort the drive by attempting to mount it on a stiff,
 non-flat surface.

 The allowable mounting surface stiffness is 80 lb/in (14.0 N/mm).
 The following equation and paragraph define the allowable mounting
 surface stiffness:

 80 lb in k = = or F x 14.0 N mm

 where k is the mounting surface stiffness (units in pounds or
 newton) and x is the out-of-plane distortion (units in inches
 or millimeters). The out-of-plane distortion (x) is determined
 by defining a plane with three of the four mounting points fixed
 and evaluating the out-of-plane defection of the fourth mounting
 point when a known force (F) is applied to the fourth point.


 Grounding
 ---------
 Signal ground (PCB) and HDA ground are connected together in the
 Barracuda 4 family drives, do not separate this connection.
 Maximizing the conductive contact area between HDA ground and
 system ground may reduce radiated emissions. A bracket shield
 with tapped holes is available to system integrators. This shield
 makes it easier to attach a braid or similar high-frequency
 grounding device. If you do not want the system chassis to be
 connected to the HDA/PCB ground, you must provide a nonconductive
 (electrically isolating) method of mounting the drive in the host
 equipment; however, this may increase radiated emissions and is the
 system designer's responsibility.


 Termination
 -----------
 The reference index signal (SSREF+) is terminated with a 2.21K ohm
 resistor. Each drive has a termination resistor located on the Main
 PCB. The terminator resistor is not removable and is always in the
 circuit. Back-feeding of current is prevented by a diode.


 Cache operation
 ---------------
 Of the 1,024 Kbytes physical buffer space in the drive, 998 Kbytes
 can be used as a cache. The cache can be divided into logical
 segments from which data is read and to which data is written.

 The drive keeps track of the logical block addresses of the data
 stored in each segment of the cache. If the cache is enabled (see
 RCD bit in the Fibre Channel Arbitrated Loop Product Manual), data
 requested by the host with a read command is retrieved from the
 cache, if possible, before any disc access is initiated. Data
 in contiguous logical blocks immediately beyond that requested
 by the Read command can be retrieved and stored in the cache
 for immediate transfer to the initiator on subsequent read
 commands. This is referred to as the prefetch operation. Since
 data that is prefetched may replace data already in the cache
 segment, an initiator can limit the amount of prefetch data to
 optimize system performance. The drive never prefetches more
 sectors than the number specified in bytes 8 and 9 of Mode page 08h
 (see Fibre Channel Arbitrated Loop Product Manual). If the cache is
 not enabled, 998 Kbytes of the buffer are used as a circular buffer
 for read/ writes, with no prefetch operation and no segmented cache
 operation.

 The following is a simplified description of the prefetch/cache
 operation:

 Case A_read command is received and the first logical block is
 already in cache:
 1. Drive transfers to the initiator the first logical block
    requested plus all subsequent contiguous logical blocks that
    are already in the cache. This data may be in multiple segments.

 2. When a requested logical block is reached that is not in any
    segment, the drive fetches it and any remaining requested
    logical block addresses from the disc and puts them in a segment
    of the cache. The drive transfers the remaining requested logical
    blocks from the cache to the initiator in accordance with the
    "buffer-full" ratio specification given in Mode Select Disconnect/
    Reconnect parameters, page 02h (see the Fibre Channel Arbitrated
    Loop Product Manual).

 3. The drive prefetches additional logical blocks contiguous to
    those transferred in step 2 above and stores them in the segment.
    The drive stops filling the segment when the maximum prefetch
    value has been transferred (see the Fibre Channel Arbitrated
    Loop Product Manual).


 Synchronized spindle operation
 ------------------------------
 Synchronized spindle operation allows several drives operating from
 the same host to operate their spindles at the same synchronized
 rotational rate. Drives operating in a system in synchronized mode
 increase the system capacity and transfer rate in a cost-effective
 manner.

 Each drive in the system can be configured by the host (using a
 Mode Select command) to operate in either the master or slave mode.
 Drives can be reconfigured by the host any time after power-up to
 be master or slave by use of the Mode Select command Rigid Disc
 Drive Geometry page. The master provides the reference signal to
 which all other drives phaselock, including the master. There is
 only one master per system, and that can be a drive or the host
 computer. All drives may be configured as slaves allowing the host
 to provide the reference signal.

 Each drive can be configured for the nonsynchronized mode in
 which it ignores any reference signal that might be present_this
 is the default mode as shipped from the factory. The connection of
 the synchronized reference signal to the host is required only if
 the host is to provide the reference signal. If the host does not
 provide the reference signal, the host should not be connected.


 Hot plugging the drive
 ----------------------
 Inserting and removing the drive on the FC-AL will disrupt loop
 operation. The disruption occurs when the receiver of the next
 device in the loop must synchronize to a different input signal.
 FC error detection mecha-nisms, character sync, running disparity,
 word sync, and CRC are able to detect any error. Recovery is
 initiated based on the type of error.

 The Barracuda 4FC disc drive defaults to the FC-AL Monitoring
 state, Pass-through state, when it is powered-on by switching the
 power or hot plugged. The control line to an optional port bypass
 circuit (external to the drive), defaults to the Enable Bypass
 state. If the bypass circuit is present, the next device in the
 loop will continue to receive the output of the previous device to
 the newly inserted device. If the bypass circuit is not present,
 loop operation is temporarily disrupted until the next device starts
 receiving the output from the newly inserted device and regains
 synchronization to the new input.

 The Pass-through state is disabled while the disc performs self
 test of the FC interface. The control line for an external port
 bypass circuit remains in the Enable Bypass state while self test
 is running. If the bypass circuit is present, loop operation may
 continue. If the bypass circuit is not present, loop operation
 will be halted while the self test of the FC interface runs.

 When the self test completes successfully, the control line to the
 bypass circuit is disabled and the drive enters the FC-AL Monitoring
 state, Pass-though state. The receiver on the next device in the loop
 must synchronize to output of the newly inserted drive.

 If the self test fails, the control line to the bypass circuit
 remains in the Enable Bypass state.

 Note: It is the responsibility of the systems integrator to assure
 that no temperature, energy, or voltage hazard is presented during
 the hot connect/disconnect (hot plug) operation. Discharge the
 static electricity from the drive carrier prior to inserting it
 into the system.


 Temperature
 -----------
 a. Operating
    The MTBF specification for the drive (800,000 hours) is based on
    operating at a local ambient temperature of 95*F (35*C).
    Occasional excursions to drive ambient temperatures to 122*F
    (50*C) may occur without impact to specified MTBF. The enclosure
    for the drive should be designed such that the case temperatures
    at the locations specified in Figures 11 and 12 are not exceeded.
    Air flow is needed to achieve these temperature values. Continual
    or sustained operation at case temperatures above these values
    may degrade MTBF.

 The drive meets all specifications over a 41*F to 122*F (5*C to 50*C)
 drive ambient temperature range with a maximum gradient of 36*F
 (20*C) per hour when the case temperature limits specified above are
 not exceeded.

 b. Non-operating
    Non-operating temperature should remain between -40*F to 158*F
    (-40*C to 70*C) package ambient with a maximum gradient of 36*F
    (20*C) per hour. This assumes that the drive is packaged in the
    shipping container designed by Seagate.



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                      F   E   A   T   U   R   E  S
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SEAGATE  ST15150FC  INSTALLATION GUIDE 83329070 REV. A  9/95

 Barracuda 4FC drives support the Fibre Channel Arbitrated Loop
 and SCSI Fibre Channel Protocol specifications to the extent
 described in this manual. The Fibre Channel Arbitrated Loop
 Product Manual (part number 77767496) describes the general Fibre
 Channel Arbitrated Loop characteristics of this and other Seagate
 Fibre Channel drives.


 Standards
 ---------
 The Barracuda 4FC disc drive is designed to be a UL recognized
 component per UL1950, CSA certified to CSA C22.2 No 950-M89, and
 VDE certified to VDE 0805 and EN60950.

 The Barracuda 4FC disc drive is supplied as a component part. It
 is the responsibility of the subsystem designer to meet EMC/
 regulatory requirements established by the FCC, DOC, and VDE.
 Engineering test characterizations of radiated emissions are
 available from the Seagate safety department.


 General description
 -------------------
 Barracuda 4FC drives are random access storage devices designed to
 support the Fibre Channel Arbitrated Loop (FC-AL) and SCSI Fibre
 Channel Protocol as described in the ANSI specifications, this
 document, and the Fibre Channel Arbitrated Loop Product Manual
 (part number 77767496) which describes the general interface
 characteristics of this drive.

 You can view the Fibre Channel interface simply as a transport
 vehicle for the supported command set (ST15150FC drives use the
 SCSI command set). In fact, the Fibre Channel interface is unaware
 of the content or meaning of the information being transported. It
 simply packs the SCSI commands in packets, transports them to the
 appropriate devices, and provides error checking to ensure that the
 information reaches its destination accurately.

 The head and disc assembly (HDA) is environmentally sealed at the
 factory. Air recirculates within the HDA through a non-replaceable
 filter to maintain a contamination-free HDA environment.

 Never disassemble the HDA. This exploded view is for information
 only. Do not attempt to service items in the sealed enclosure
 (heads, media, actuator, etc.) as this requires special facilities.
 The drive contains no parts replaceable by the user and opening the
 HDA for any reason voids your warranty.

 Barracuda 4FC drives use a dedicated landing zone at the innermost
 radius of the media to eliminate the possibility of destroying or
 degrading data by landing in the data zone. The heads automatically
 go to the landing zone when power is removed from the drive.

 An automatic shipping lock prevents potential damage to the heads and
 discs that results from movement during shipping and handling. The
 shipping lock disengages and the head load process begins when power
 is applied to the drive.

 Barracuda 4FC drives decode track 0 location data from the dedicated
 servo surface to eliminate mechanical transducer adjustments and
 related reliability concerns.

 The drives also use a high-performance actuator assembly design that
 provides excellent performance with minimum power dissipation.


 Standard features
 -----------------
 Barracuda 4FC drives have the following standard features:

 - Integrated dual port FC-AL controller

 - Support for FC-AL (Fibre Channel Arbitrated Loop)

 - Differential copper FC drivers and receivers

 - Downloadable firmware using the FC-AL interface

 - Drive selection ID and configuration options are set on the FC-AL
   backpanel, T-card, or through interface commands. Jumpers are not
   required on the drive.

 - FC world-wide name uniquely identifies the drive and each port

 - Supports up to 16 initiators

 - User-selectable logical block size (180 to 4,096 bytes)

 - Reallocation of defects on command (Post Format)

 - User-selectable number of spare sectors per cylinder

 - Industry standard 3.5-inch full-high form factor dimensions

 - Programmable sector reallocation scheme

 - Flawed sector reallocation at format time

 - Programmable autowrite and read reallocation

 - Reallocation of defects on command (post format)

 - 96-bit Reed-Solomon error correction code

 - Sealed head and disc assembly (HDA)

 - No preventive maintenance or adjustments required

 - Dedicated head landing zone

 - Automatic shipping lock

 - Automatic thermal compensation

 - Embedded Grey Code track address to eliminate seek errors

 - Self-diagnostics performed at power on

 - 1:1 interleave

 - Zone bit recording (ZBR)

 - Vertical, horizontal, or top down mounting

 - Dynamic spindle brake

 - 998 Kbyte data buffer


 Media description
 -----------------
 The media used on the drive has a diameter of approximately 95 mm
 (approximately 3.7 inches). The aluminum substrate is coated with
 a thin film magnetic material, overcoated with a proprietary
 protective layer for improved durability and environmental
 protection.


 Performance
 -----------
 - Programmable multi-segmentable cache buffer

 - 106.3 Mbytes/sec maximum instantaneous data transfers

 - 7,200 RPM spindle; average latency = 4.17 msec

 - Command queuing of up to 64 commands

 - Background processing of queue

 - Supports start and stop commands

 - Provides synchronized spindle capability

 - Adaptive seek velocity; improved seek performance


 Reliability
 -----------
 - 800,000 hour MTBF (Class A computer room environment)

 - Fibre Channel (FC) interface transports SCSI protocol through CRC
   protected frames

 - LSI circuitry

 - Balanced low mass rotary voice coil actuator


 Unformatted and formatted capacities
 ------------------------------------
 The standard OEM models are formatted to 512 bytes per block.
 ST15150FC drives have nine (9) spare sectors per cylinder and one
 spare cylinder per unit.

 Users having the necessary equipment may modify the data block
 size before issuing a format command and obtain different
 formatted capacities than those listed. User-available capacity
 also depends on the spare reallocation scheme you select. See the
 Mode Select command and the Format command in the Fibre Channel
 Arbitrated Loop Product Manual (part number 77767496).


 Factory-installed accessories
 -----------------------------
 OEM standard drives are shipped with the Barracuda 4FC Installation
 Guide (part number 83329070).


 Factory-installed options
 -------------------------
 You may order the following items which are incorporated at the
 manufacturing facility during production or packaged before
 shipping:

 - Black plastic front panel with green lens (part number 70553702).*

 - Black plastic front panel with red lens (part number 70553701).*

 - Single-unit shipping pack. The drive is normally shipped in bulk
   packaging to provide maximum protection against transit damage.
   Units shipped individually require additional protection as
   provided by the single unit shipping pack. Users planning
   single unit distribution should specify this option.

 * You may order other front panel colors. Each panel has a single
   rectangular LED indicator lens that, when glowing, indicates
   the drive is selected.


 User-installed accessories
 --------------------------
 The following accessories are available. All kits may be installed
 in the field.

 - Front panel kit (green lens), part number 70869751.

 - Single-unit shipping pack kit.

 - Adapter accessory frame kit, part number 75790701. (adapts a
   3.5-inch drive to fit in a 5.25-inch drive mounting space).
   This kit contains the frame to allow a 3.5-inch drive to be
   mounted in a 5.25-inch drive bay. It includes mounting hardware,
   front panel with a green lens, an LED with cable that connects
   to the remote LED connector, and installation instructions.

 - Evaluation kit, part number 70935895. This kit provides an
   adapter card ("T-card") to allow cable connections for two FC
   interfaces and DC power. Two twin axial cables, 6-feet in length,
   are included for the input and output connections to the FC
   interfaces. A small DC fan is included for cooling.

 All performance characteristics assume that thermal calibration is
 not in process when the SCSI command is received. A SCSI command
 being executed is not interrupted for thermal calibration. If
 thermal calibration is in process when a SCSI command is received,
 the command is queued until the compensation for the specific head
 being calibrated completes. When compensation completes for the
 specific head being calibrated, the first queued SCSI command is
 executed.


 Thermal calibration
 -------------------
 ST15150FC drives use an automatic thermal calibration (TCAL) process
 to maintain accurate head alignment with the data cylinders. The host
 system may choose to allow the drive to perform TCAL at the drive's
 predefined intervals or the Rezero Unit command may be issued by the
 host to reset the TCAL timer so that the host knows when the TCAL
 will occur.

 1. At power up and following a SCSI reset, the drive calibrates all
    of the heads before any read or write com-mands are processed.
    All heads are also calibrated during the SCSI Rezero Unit
    command.

 2. The drive delays 300 seconds before initiating any TCALs. No
    TCALs occur during this delay period.

 3. A single-head TCAL is then scheduled at 7.1 second intervals.

 4. After the drive TCALs all of the heads, the interval is increased
    to schedule a single head TCAL every 14.3 seconds.

 5. The drive attempts to find an idle period of 25 to 50 milliseconds
    prior to performing a single head TCAL. If this TCAL is delayed
    for another interval of time, the drive forces the TCAL at the
    next command boundary. This guarantees that no head will remain
    uncalibrated for more than 600 seconds (2 * 21 heads * 14.3
    seconds per head) and that no TCALs are closer together than the
    interval time.

 Note. Any TCAL performed during the "standard" retry sequence is
       limited to the failing head and is disabled if the host has
       selects a retry count of zero.


 Defect and error management
 ---------------------------
 The drive, as delivered, complies with this product manual. The read
 error rates and specified storage capaci-ties are not dependent upon
 use of defect management routines by the host (initiator).

 Defect and error management in the SCSI protocol involves the drive
 internal defect/error management and FC-AL system error considera-
 tions (errors in communications between the initiator and the
 drive). Tools for use in designing a defect/error management plan
 are briefly outlined in this section. References to other sections
 are provided when necessary.


 Drive internal defects/errors
 -----------------------------
 Identified defects are recorded on the drive defects list tracks
 (referred to as the primary or ETF defect list). These known defects
 are reallocated during the initial drive format operation at the
 factory. See the Format Unit command in the Fibre Channel
 Arbitrated Loop Product Manual (part number 77767496). Data
 correction by ECC is applied to recover data from additional
 flaws if they occur.

 Details of the SCSI commands supported by the drive are described in
 the Fibre Channel Arbitrated Loop Product Manual. Also, more
 information on the drive Error Recovery philosophy is presented in
 the Fibre Channel Arbitrated Loop Product Manual.


 Physical description
 --------------------
 ST15150FC drives may be connected in a loop together or with other
 compatible FC-AL devices. A maximum of 127 devices may have
 addresses; however, one of the addresses is reserved for a fabric
 port switch device. This means 126 addresses are available for FC-AL
 devices. More FC-AL compatible devices may physically reside on the
 loop, but they will not be functional because they would not be able
 to obtain valid addresses.

 Port bypass circuits (PBCs) allow devices to be inserted into
 unpopulated locations or removed from the loop with loop opera-
 tion recovery after a brief disruption. These PBCs are located
 external to the FC-AL device.


 Power
 -----
 Power is supplied through the FC-SCA with support for +5 volts and
 +12 volts. All of the voltage pins in the drive connector are the
 same length.

 Four 12 volt pins provide +12 volt power to the drive.
 The current return for the +12 volt power supply is through the
 common ground pins. The supply current and return current must be
 distributed as evenly as possible among the pins. The maximum
 current typically occurs while the drive motor is starting.
 Three 5 volt pins provide logic power to the drive. The current
 return for the +5 volt power supply is through the common ground
 pins. The supply and return current must be distributed as evenly as
 possible among the voltage and ground pins.

 The mating connector pins use shorter contacts to achieve power
 surge reductions and to aid in "hot plugging" the drives. There
 are longer voltage contacts in the connector to enable the drive
 filter capacitors to charge. Current to the drive through the long
 charge pins is limited by the system in which the drive operates.
 Three of the +12 volt pins are shorter to allow capacitive pre-
 charging through the longer +12 volt charge pin. Two of the +5
 volt pins are shorter to allow capacitive precharging through
 the longer +5 volt charge pin.


 Fault LED out
 -------------
 The Fault LED Out signal is driven by the drive when:

 - the drive detects failure of both ports

 - the drive detects an internal disc failure

 - the drive receives the appropriate fault LED command from the
   host

 The Fault LED Out signal is designed to pull down the cathode of
 an LED. The anode is attached to the proper +5 voltage supply
 through an appropriate current limiting resistor. The LED and
 the current limiting resistor are external to the drive.


 Synchronized spindles interface
 -------------------------------
 The synchronized spindles interface (SSI) allows several drives
 operating from the same host to operate their spindles at a
 synchronized rotational rate.


 Electrical description of the SSI
 ---------------------------------
 The electrical interface consists of one digital TTL reference
 index signal and ground. The reference index signal (SSREF+) is
 an output if the drive is configured as a master and is an input
 otherwise.



**********************************************************************
                      G   E   N   E   R   A   L
**********************************************************************
SEAGATE   FC-AL INTERFACE


 An Overview of Fibre Channel
 ---------------------------

 Introduction
 ------------
 Everyone has accepted the fact that we have moved into the Age of
 Information. In this paradigm information itself is a commodity, and
 therefore there is great value in its efficient disbursement.

 Unfortunately, industry has placed greater value in creating
 information, than distributing it. We often hear about new machines
 which are capable of performing prodigious calculation at the blink
 of an eye. New reports of ever faster computers are commonplace.

 Sharing this information, however, has become a priority only
 recently. It seems that although we have moved into the Age of
 Information, one of our biggest challenges is to efficiently
 distribute the information for everyone to use.

 Luckily, a viable solution is at hand. Conceived and supported by
 such industry giants as IBM, Hewlett-Packard, and Sun Microsystems,
 the Fibre Channel is aimed at providing an inexpensive, flexible and
 very high-speed communications system. Most of the popular network
 implementations today can claim to have any two of these elements.
 Since Fibre Channel encompasses all three, it has everything
 necessary to become a resounding success.

 Not the Network
 Fibre Channel has significant advantages over common networks. The
 first difference is speed. The fastest network implementations today
 support transfer data at a little over 100 megabits per second. For
 smaller data files, where a single computer is directly communicating
 with a file server, such speeds are adequate. However, for realtime
 video and sound, or systems where two machines must operate on common
 data even 200 megabits per second is hopelessly inadequate. Fiber
 Channel provides significantly higher rates, from 10 to 250 times
 faster than a typical Local Area Network (LAN). In fact, Fibre
 Channel can transfer data at speeds exceeding 100 megabytes, or 800
 megabits, per second. This speed is sufficient to allow transfer of a
 1024x768 image with 24-bit color at 30 frame per second, and CD-
 quality digital sound.

 This overcomes the bandwidth limitation, which is probably the most
 serious impediment  for LAN performance. As the number of computers
 communicating on a common network increases, the amount of data
 packets increases accordingly.

 This is because data on a LAN is common to all computers on that
 network. The software must decide if a particular message is relevant
 for a particular machine. When several machines are communicating
 with one another, every other machine on the network must contend
 with all of the messages. As the number of messages increases, the
 load for the entire system is increased.

 Fiber channel is a switched system. Much like a telephone system, a
 connection is established between only the parties that need to
 communicate. These parties can share the entire bandwidth of Fibre
 Channel, since they do not have to contend with messages not relevant
 to their communication. LANs attempt to compensate for this by
 increasing the transfer speed, which places an even greater burden on
 the software. Since all protocol for Fibre Channel is handled by
 the hardware, the software overhead is minimal. Fibre Channel also
 supports full parallelism, so if greater capacity is needed, more
 lines can be added. The common analogy for showing the advantages of
 parallelism is the effect of doubling the number of lanes on a
 freeway instead of doubling the speed limit.

 The physical distance between computers is another limiting factor
 for conventional LANs. Ethernet cables usually have a limit of 1000
 feet between machines whereas Fibre Channel can support a link
 between two up to 10 kilometers apart.

 Finally, Fibre Channel is not software intensive. All of the
 essential functions are  handled by hardware, freeing the computer's
 processor to attend to the application at hand. Even the error
 correction for transmitted data is handled by the Fibre Channel
 hardware. In standard LANs this requires precious processor
 resources.


 Advantages for Computing
 ------------------------
 The obvious advantage for Fibre Channel is to facilitate
 communication between machines. Several workstations clustered
 together already surpass the speed and capacity of a VAX, and begin
 to rival the power of a super computer, at a much lower cost. The
 power of concurrent processing is awesome. For example, a single
 neuron inside our brain is much less complex, and operates far slower
 than a common 286 processor. However, millions of neurons working in
 parallel can process information much faster than any processor known
 today. Networking simple logical units, and operating them in
 parallel offers advantages simply unavailable for the fastest single
 processor architectures. These shared architectures require a huge
 amount of communication and data sharing which can only be handled by
 high-speed networks. Fibre Channel not only meets these requirements,
 but meets them inexpensively.

 The hardware industry is partly responsible for the I/O bottleneck.
 By using the processor speed as the primary focus for their sales
 efforts, the bus speeds have languished. With respect to the new
 class of processors, current system bus speeds  are greatly lagging.
 This is something like building a mill which can process 1000 pounds
 of grain a day, and supplying that mill with a single donkey. There
 is little use for a fast processor that spends most of its time
 waiting for data to act upon.  Whether this data comes from disc
 drives, peripherals, or even other processors, today's bus speeds
 would leave most processors idle, and the next generation of
 processors will be many times faster. Fiber Channel provides the
 data transfer capability which can keep current and upcoming
 processors busy.


 Impact on Mass Storage
 ----------------------
 Today's fastest interfaces are capable of transferring data at around
 20 megabytes per second. However, this speed rating is only for
 transferring data. All protocol intercommunication occurs at  much
 slower speeds, resulting in a lower effective data transfer rates,
 typically around 11 megabytes per second. This represents about
 one-tenth of Fibre Channel's current capability. Fibre Channel drives
 do not suffer from device protocols occurring at slower speeds, since
 all communication occurs at 100 megabytes per second, including
 device intercommunication. In addition to this, the drive itself can
 be placed up to 10 kilometers away from the computer. This would have
 two effects on the way mass storage is implemented.

 First, the amount of data a machine could receive would only be
 limited to the transfer speed of the drive. For high performance disc
 arrays this could exceed 50 megabytes per second. Machine and disc
 storage could finally work to provide real-time, full motion video
 and sound for several machines simultaneously. With Fibre Channel's
 ability to work across long distances, these machines could
 conceivably reside many miles apart. For medical applications,
 computer design centers, and real-time networks such as reservations
 systems, this capability would be invaluable.

 Second, such support for transmitting data over large distances would
 allow disc drives to be placed away from the computer itself. This
 would allow for centralized data resource areas within a business
 office, simplifying everything from site planning to maintenance
 procedures. Indeed a centralized data resource center would be
 possible for an entire office complex.

 The development of the Loop will also provide a huge advantage in
 implementing large capacity disc sub systems. The Fast/Wide SCSI
 specification has a theoretical upper limit of 16 total devices
 attached to a single host. The practical maximum is 6 devices. Fibre
 Channel supports a theoretical limit of 256 devices for a common
 host, with a practical implementation of 64 devices. This practical
 limit is a very conservative figure, and implementation with more
 devices are easily possible. The Loop allows system designers to
 build high capacity configurations, well into the terabyte range,
 with much lower overall cost.

 Finally, Fibre Channel is a serial communications device which has
 two immediate advantages. First, the cabling necessary to
 interconnect Fibre Channel devices is very inexpensive when compared
 to SCSI cabling. Fibre Channel cabling is also much easier to
 connect, and replace than SCSI cables, which simplifies the entire
 process of integration and maintenance for a high capacity data
 storage system. For corporations that are currently grappling with a
 the complexity of installation, and high-cost of SCSI cables, this
 feature will prove invaluable for cutting costs and simplifying
 installation and upkeep.

 Secondly, implementing Fibre Channel requires less space on the
 circuit board than SCSI drives. This reduced space requirement would
 allow the drive designers to include extended features which cannot
 currently be implemented. For example, a 3.5-inch form-factor drive
 with Fibre Channel could be designed with  dual-port capability, a
 feature necessary for use with many mainframes and mini-computers.
 The space saved on the circuit board by using Fibre Channel would
 allow for the extra connector and additional circuitry needed for
 dual-port drives.


 Conclusion
 ----------
 The Fibre Channel will provide the corporations with data in much the
 same way the freeway system provided motorists mobility. Access to a
 vast, interconnected information network which is fast, inexpensive,
 and flexible. With the adoption of Fibre Channel as an open ANSI
 standard, its effect on the horizon of computing will be nothing
 short of revolutionary.

 We have become very good at processing data; Fibre Channel allows us
 to move it. The ability to share information will provide the impetus
 for communication, design and development on a scale not previously
 possible. By facilitating the fabled data-highway, Fibre Channel
 will accelerate  to the Age of Information, as the steam engine moved
 us into the Age of Industry.


