IBM 2104 Model DU3 - Manual (Page 56)

Single-Bus Mode Configurations
For a single-bus mode configuration, the SCSI Bus Split switch on the switch card
of a 2104 Model DU3 must be set to Off.
Each 2104 Model DU3 can be connected to one external SCSI connector on a
SCSI adapter card, or to one integrated SCSI port, in a using system. If an adapter
card has four external SCSI connectors, it can be connected to up to four 2104s
(Model DU3 or TU3).
For High Availability Cluster Multi-Processing (HACMP) configurations, the two
SCSI interface cards in a 2104 are connected either to external SCSI connectors on
adapter cards, or to integrated Ultra2 SCSI ports, in two different using systems.
The adapter cards must be a PCI Dual-Channel Ultra2 SCSI Adapters (Type 4-R,
feature 6205) or a PCI Dual-Channel Ultra3 SCSI Adapter (type 4-Y, feature 6203).
For non-HACMP configurations, the SCSI interface cards in a 2104 can be
connected either to an external SCSI connector on an adapter card, or to an Ultra2
SCSI integrated port, in a using system. Each adapter card must be a PCI
Dual-Channel Ultra2 SCSI Adapters (Type 4-R, feature 6205) or a PCI
Dual-Channel Ultra3 SCSI Adapter (type 4-Y, feature 6203). The adapters can be in
the same using system or in two different using systems. However, they must not
share access to the disk drives in the 2104.
40 2104 Model DU3 Installation Guide