When used with other external SCSI drives, a Macintosh SE or Macintosh II
equipped with an internal SCSI drive may develop compatibility problems,
such as the inability to boot up without crashing. This happens because:
- The Macintosh internal SCSI drive and the external hard drive have the
same SCSI priority number.
- The external drive contains an older driver that will not work with the
newer Macintoshes.
The first problem pertains only to those external SCSI drives that have
the SCSI priority number set to 0 in their firmware, such as the AST 4000.
Although AST drives are presently jumpered to have a priority number of 0,
AST is replacing the jumper block on the 4000 with a dip switch, which
will make changing the priority easier. The priority numbers in other AST
and external Rodime drives are either set to a number other than 0 or can
be changed easily. A customer who needs to change the priority number of a
AST 4000 should contact AST for complete directions.
The workaround to the second problem is simply to update or reinitialize
the driver using the Apple HD SC Setup.