As far as I know, bootable CDs have the SCSI driver on a hidden partition, thus you don't need to have a Hard Disk with a suitable CD driver -- but it will be needed if no disk is in the CD drive.
Upon startup, the SCSI-manager in ROM asks every device in the SCSI chain for a driver. If such thing is available, it gets loaded into RAM and full access to the device is granted -- that's the way HDs work!
That should work fine; however, some drivers may be incompatible with some computers/systems. I believe Apple's CD-ROM driver (which is the usually installed one in bootable CDs) will only work with Apple-branded drives, be them internal or external.
Upon startup, the SCSI-manager in ROM asks every device in the SCSI chain for a driver. If such thing is available, it gets loaded into RAM and full access to the device is granted -- that's the way HDs work!
That should work fine; however, some drivers may be incompatible with some computers/systems. I believe Apple's CD-ROM driver (which is the usually installed one in bootable CDs) will only work with Apple-branded drives, be them internal or external.