IBM1S506 Beta Driver Documentation
               ----------------------------------


        Enclosed is the IBM1S506.ADD. It contains a number
        of changes from the previous driver. This note is
        intended to help explain those changes.


        Summary of Changes
        ------------------

        Multiple Controller support

        - 2 independent controllers can be supported per instance
          of this driver.

        - Multiple instances of the driver may be loaded


        Improved Geometry Support and  >1024 Cyl support

        - The driver will attempt to determine drive geometry
          by the following methods:

          -- Via command line switches
          -- Via an IDENTIFY command issued to the drive
          -- Via the Fixed Drive Tables

          This driver will support disks >1024 cylinders
          if indicated by one of the above geometry sources.

        - The driver can display the BIOS (Int 13), IDENTIFY,
          Command Line geometries and the geometry selected
          by the driver.


        Error Handling/Recovery

        - The driver no longer issues "Power Management"
          commands.

          Regardless of what CAM states there appears to
          be no industry wide consensus on what these commands
          should be. In addition sufficient attention has
          not been paid to compatibility issues with older
          MFM/RLL and IDE controllers.


        - Error recovery is driven by elapsed time

          Error recovery in this driver has been restructured.
          When an error occurs, retries will be done periodically
          over a set time interval. This should allow drives which
          have "spun-down" to recover.

        - Soft-Reset used to help clear error conditions

          The driver will issue a soft reset via 3F6 to recover
          from timeouts and from persistent error conditions.


        - Compatibility of external IDE adapters with PS/2 chip sets

          PS/2 chip sets provide an integrated IDE port. This
          driver will detect of an external IDE adapter is
          present prior to enabling the internal PS/2 IDE
          ports.



        Command Line Switches
        ---------------------

         Sample Command Lines:

         BASEDEV=IBM1S506.ADD /V /A:0 /U:0 /T:10 /GEO:(1314,7,26,-1) /A:1 /I

         BASEDEV=IBM1S506.ADD /V /A:1 /P:120 /IRQ:11 /U:0 /T:10

         BASEDEV=IBM1S506.ADD /V /A:1 /U:0 /GEO:20

         BASEDEV=IBM1S506.ADD /V /A:0 /U:0 /SMS

         BASEDEV=IBM1S506.ADD /V /A:0 /!R


         Switch definitions:

           /V = Verbose Mode

           Displays controller status and drive geometry information
           during OS/2 initialization.


           /A:0 = Adapter number

           Adapter 0 has default parameters for a primary adapter.
           Adapter 1 has default parameters for a secondary adapter.


           /U:0 = Unit Id

           Unit 0 indicates parameters apply to the master unit.
           Unit 1 indicates parameters apply to the slave unit.


           /T:10 = Error retry time in seconds. (dec)

           Indicates the total allowable error recover time for
           a request. Error recovery times < 5 seconds will be
           ignored. This parameter defaults to 30 seconds. A shorter
           interval may be desirable for fault tolerant applications.


           /GEO:(1314,7,26,-1) or /GEO:20 = Drive geometry override (dec)

           Indicates the Cylinder/Head/Sector geometry for the drive.
           The fourth parameter is the Write Precompensation Cylinder
           which may be omitted for drives which do not require
           precompensation.

           As an alternate format standard BIOS drive types may
           be used. Types (0-47) are supported. User defined types
           48, 49 should be entered directly by in the previous
           format.

           When specified, this parameter overrides other geometry sources.
           If this parameter is absent, other geometry sources discussed
           above will be used.


           /I = Ignore adapter

           The driver automatically attempts to locate and initialize
           both the primary and secondary adapters. In some cases other
           DASD controllers may appear between the primary and secondary
           IDE controllers. In these cases the system should be configured
           as follows:

           BASEDEV=IBM1S506.ADD /V /A:1 /I
           BASEDEV=MOREDASD.ADD
           BASEDEV=IBM1S506.ADD /V /A:0 /I


           /!R = Disable adapter resets

           Disables adapter resets. In most cases resets are beneficial
           to assist in recovering from transient hardware problems
           such as lost interrupts, timeouts, or commands a particular
           adapter may not support.

           However, for some ESDI adapters, options set by vendor
           unique commands such as 'Sector Sparing' may be lost after
           after a reset. Setting this switch is recommended for ESDI
           adapters with disks formatted using 'Sector Sparing'.


           /P:120 or /PORT:120 = Base Port address (hex)

           Overrides the default Base Port address for this adapter.
           Ports are still assigned in this case would be (120-127) and
           (326). The default port addresses for Adapter 0 is (1F0) and
           for Adapter 1 is (170).


           /IRQ:11 = IRQ Number (dec)

           Overrides the default IRQ Number for this adapter. The default
           IRQ address for Adapter 0 is (14) and for Adapter 1 is (15).


           /SMS = Enable Set Multiple Mode support

           This switch enables Set Multiple Support which the improves
           performance of some IDE drives. If the drive does not have
           this feature, this switch will be ignored. The /V - (Verbose)
           option will indicate whether this feature has been enabled
           on a particular drive.