In the PC-world and in most modern SCSI-BIOS-setups, SCSI-hard disks
are assigned to the drive letters, starting with the lowest SCSI-id
(physical number -- pun) to be drive C:, as seen from DOS and
similar operating systems. When looking into papers describing the
ANSI-SCSI-standard, this assignment of drives appears to be wrong.
The SCSI-standard follows a hardware-hierarchy which says that id 7
has the highest priority and id 0 the lowest. Therefore, the host
adapters are still today everywhere placed as SCSI-id 7 by default.
In the SCSI-standard, the drive letters express the priority of the
disk. C: should be the hard disk, or a partition on it, with the
highest priority. This must therefore be the disk with the highest
SCSI-id (e.g. 6) and not the one with the lowest! IBM-BIOS kept the
original definition of the SCSI-standard as also industrial- and
process-control-machines, like VME-CPUs running under realtime-OSes
(e.g. LynxOS, OS9) do.

If you like to run Linux on your MCA-machine with the same
assignment of hard disks as seen from e.g. DOS or OS/2 on your
machine, which is in addition conformant to the SCSI-standard, you
must say Y here. This is also necessary for MCA-Linux users who want
to keep downward compatibility to older releases of the
IBM-MCA-SCSI-driver (older than driver-release 2.00 and older than
June 1997).

If you like to have the lowest SCSI-id assigned as drive C:, as
modern SCSI-BIOSes do, which does not conform to the standard, but
is widespread and common in the PC-world of today, you must say N
here. If unsure, say Y.