Before the uproar begins, there is no competitior for real computing. Once you go SCSI, nothing else is quite the same...

ST412 / ST506 Drive Interface

   The drive controller sits on a card. There is no drive controller on a device.

IDE Drive Interface

   The slot may take the guise of an embedded port or a paddleboard plugged into a system slot. The IDE/EIDE disk controller is embedded in each device. Each drive sits on the bus. Newer ATA drives employ bus mastering. Better late than never...
 

SCSI Device Controller Interface

   The blessings of SCSI: reliable support of external devices, different devices, more devices (ranges from 7 to 15 devices). SCSI may appear as a built-in port, however it still provides a seperate signal bus to attached devices.