self-booting distribution disk does not autoboot

I have a copy of Red Hat 7.3 that auto-booted on one machine, but
won't on my current machine, and I'm trying to track down just why
(perhaps SCSI BIOS configuration).

First, I'd like to confirm that the executable script ("autoboot") on
the first distribution disk is what should start the
installation/upgrade routine. I'd like to confirm also that if I boot
my machine with the disk in the drive, the installation program on the
cdrom disk should automatically come up.

This might seem obvious, but I just want to touch those two bases to
make sure.

I gather there are several conditions necessary for the autorun to
boot the disk:

a) The motherboard must support self-booting cdrom disks. My
motherboard is fairly new (Intel D850MV), and its (Award) BIOS
(upgraded, and so quite new) has an option to set the priority list of
bootable devices, and this includes my SCSI CDROM drive. This I assume
means that self-booting cdrom disks are supported.

b) In the motherboard BIOS, all that is necessary is that the CDROM be
specified as a device to be probed for a boot sector before my HD
is. I've done that, and also specified that the second bootable device
be my floppy drive; a bootable disk in it works fine. In BIOS I've
disabled PnP, which I gather is appropriate for Linux.

c) The CDROM drive must be functional. Since I can mount it just fine
under Linux and access it, I assume it is functional.

d) Here comes the real question. My Adaptec 39160 SCSI adapter BIOS
has a section, Boot Device Configuration, in which the Int13 support
(for PnP) is enabled by default, and that means there can be no
support for CDROM drive boot support. But I've tried to enable and
disable suport for Int13 (which shouldn't make any difference for
Linux) without luck.

Haines Brown