IBM ServeRAID-4 Ultra160 Series User Reference page 25

ServeRAID-4L and ServeRAID-4Lx controller
The ServeRAID-4L and ServeRAID-4Lx controllers have one independent SCSI
channel connector, Channel 1. This SCSI channel supports up to 15 physical
devices.
Internal Channel 1
External Channel 1
Figure 3. ServeRAID-4L controller
Internal Channel 1
External Channel 1
Figure 4. ServeRAID-4Lx controller
You can attach internal SCSI devices to the internal Channel 1 connector. You can
attach external SCSI devices to the external Channel 1 connector. The
ServeRAID-4 controllers do not support configurations that use both the internal and
external connectors concurrently on the same channel. For example, you cannot
use both external Channel 1 and internal Channel 1.
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Chapter 1. Product information