IBM 2104 Model DU3 - Manual (Page 69)

Configurations That are Not Valid
This section gives some examples of configurations that are not valid.
Two Adapters in One Using System Connected to One 2104
1 SCSI interface card
2 SCSI adapter. This configuration is not valid for any type of adapter.
Note: This configuration is not valid when the 2104 is configured in single-bus
mode, but is valid when the 2104 is configured in dual-bus mode. See page
48.
Using System 2104 Subsystem
1 1
2
2
X
Figure 38. Two Adapters in One Using System Connected to One 2104 (Single-Bus Mode).
This configuration is not valid.
Appendix A. Operating with RISC Systems 53