DATE: 8 Aug 1990
        
        PRODUCT: M2266S
        
        NUMBER: 002
        
        SUBJECT: System Installation
        
        Many  of the present computer systems that have a SCSI  interface 
        use  the  SCSI  Group 0 commands as part  of  their  SCSI  driver 
        routines.   The  Group  0  commands are limited  to  21  bits  of 
        addressing,  therefore, the maximum number of blocks that can  be 
        addressed is 2097152 (0x1FFFFF) (This means a maximum capacity of 
        1.0737GB).  The  Humming 6 with factory  parameters  has  2107704 
        (0x202938)  blocks(1.0791GB), which is over the number of  blocks 
        addressable by Group 0 commands.
        
        Some  software drivers actually wrap around when they  reach  the 
        Group 0 maximum block count, that is, they go from 0x1FFFFF  back 
        to 0x000000.  They do not check if the drive exceeds the  maximum 
        number  of  blocks.   This will cause  major  problems,  as  data 
        written on the lower addresses of the disk will be overwritten if 
        the system writes data to the high order addresses.
        
        Some  software drivers do not do a check for the maximum  address 
        of  0x1FFFFF and try to use the full address range of the  drive.  
        If the maximum block count of the Humming 6 is used in a Group  0 
        command, the command will try to select LUN 1.  This will cause a 
        check  condition from the Humming 6 and a catastrophic error  for 
        the software driver.
        
        The following is a list of some of the computer systems and  host 
        adapters that have been tested with the Humming 6.
        
             SUN OS 4.03 and 4.1
                  Can be made to work by defining a lower cylinder
                  count during the format function.
                  Will require a new software driver to use full capacity
                  of drive.
        
             DEC VMS 5.3
                  Can be successfully installed but no way can be
                  found to define a lower number of addressable
                  blocks.  Will require a new software driver.
        
             Apple Macintosh Drivers
                  Disk Manager driver
                       Will only work if usable partition size 
                       is adjusted lower than default.
                  LaCie Cirrus driver
                       Can be installed but cannot adjust number of 
                       blocks
        
             PC DOS
                  Disk Manager
                       This driver will only define 1023 cylinders, 
                       64 heads and 32 sectors, which is below the 
                       maximum block count for a Group 0 command.
        
        
        A solution to the problems encountered by using Group 0 commands, 
        other  than  writing new drivers using Group 1 commands,   is  to 
        have the drive reformatted using 1648 cylinders, instead of 1658.