@tone007
As I recall, you still can't get to the early startup menu with the A3000 in this state. Essentially the SCSI controller enters an endless loop or something which causes the entire machine to hang during boot.
..right, I should've added if the 3000 were working properly.
This reminds me of when I was 12 and tried to stick a 64K Apple II memory board into an IBM XT. The slot was the same size! Seriously, though, I can't imagine confusing a parallel CDROM for SCSI one, the lack of SCSI ID selection on the drive would be a dead giveaway.