A quick google seems to confirm that SBM doesn't support SCSI devices.
However, I did find this page
http://www.redhat.com/docs/manuals/ente ... cdrom.html
which explains how to make boot diskettes for RHEL 3
I wonder if RHEL 4 has the same stuff on the CD ?
Note that to use a SCSI CDROM you need a driver diskette as well as a boot one.
Suggestion - why not borrow an IDE CD-ROM and connect it up just for the install ?