The motherboard SCSI controller chip was the problem with the Buss. Most production machines had WD controller chips with either -04 or Proto stamped on them. They were flawed, and adding a drive on the external SCSI port could cause the SCSI Buss to lock-up. The only cure was the WD -08 chip, or a separate SCSI controller card for the A3000.
I was very successful with 2 hard drives attached to the internal SCSI port, and with a GVP HC8+ SCSI controller controlling four separate SCSI devices.
