Apple WS 9650 manual

Basics	Ultra Wide SCSI - 31
	There is a 50-pin, SCSI-1 Slow connector on the logic
	board; however, the 50-pin SCSI Fast bus should be used in
	most cases because it offers better performance. A total of
	seven devices can be attached to the SCSI-1 bus, which
	transfers data at a maximum rate of 5 MB/s.
	All devices on the same SCSI bus must have unique ID
	numbers, but devices on different SCSI buses may use the
	same SCSI ID number. (For example, you could have a CD-
	ROM drive with ID number 3 connected to the Fast SCSI-2
	bus and a hard drive with ID number 3 connected to the Ultra
	Wide SCSI-3 bus.) See “Ultra Wide SCSI” above for more
	information about assigning SCSI ID numbers on the Ultra
	Wide SCSI-3 bus.
	The graphic on the following page shows the routing of the
	two SCSI cables (50-pin and 68-pin) in the WS 9650.