Originally had a similar issue to the person on this thread http://68kmla.org/forums/viewtopic.php?f=6&t=16291 however my issue was resolved when removing the external SCSI terminator as the drive had the resistors on it.
After removing the external terminator, the gs did boot via floppy and the hard drive would mount however after fiddling (i.e. removing the external drive from the card) the gs now boots to about 75% through and then it crashes to the monitor prompt. This now occurs even if the drive powered off or is not connected. Once the SCSI card is removed, the gs will boot with no issues using the same floppy that failed previously.
The 2gs has a rom 3 installed. I've tried booting from an OS 5.4 floppy and an OS 6 floppy, both do the same thing. The SCSI card is the standard Apple one (not high speed) model 607-0291-A with the eprom labeled 2.0. I have it in slot 6 currently but tried it in slot 7 (both are set to "Your Card") and get the same results. The boot sequence is set to boot from slot 5 as I was in the process of trying to get the drive partitioned properly and the OS installed on it.
Did I somehow fry the SCSI controller? Would getting a new eprom for it help? Any assistance would be greatly appreciated. Thanks!