IBM 5155 Manual To Operations page 388

The IBM Cluster Adapter can be installed in your
system unit or your expansion unit. If your are installing
this option in your IBM Portable Personal Computer, it
can only be installed in expansion slot 2.
When you have completed installation of the Cluster
Adapter, contact your Installation Manager for
~.
installation of the coaxial cable.
To install this option go to "Option Installation" in the
Guide to Operation.
12 Cluster Adapter
January 1984