My system has a primarily SCSI system, (All scsi disks, 1 cdrom burner, on a buslogic bt958 controller), but with ONE IDE cdrom (primary master) I can boot the redhat CD off of either cdrom, SCSI or IDE. The problem is that when booting from the SCSI CDrom. The installer never asks to load a SCSI module, and subsequently keeps tryin to access "hda" (IDE cdrom) instead, and prevents me from going further. I did NOT try removing the IDE drive and installing (which I think would work), instead I jsut used the IDE drive to install, but it the installer should take care of this condition GRACEFULLY and still prompt the user to load a driver (for SCSI) EVEN if IDE devices are still there.. In EXPERT mode it DID NOT. I did manage to get by this one, but other less experienced users may run into trouble...
this is probably hardware specific ... using 6.2 I cannot reproduce this behavior (ie the buslogic module is loaded properly by the installer) using the Buslogic BT 948 (closest test lab hardware)