IBM RT User's Setup Manual page 318

You can install this adapter in slots 2, 4, 5, 7, and 8 in
In sta llin g :
Model 25 and in slots 2 through 5 in Model 10, whichever is
available. See the system unit diagram for the correct slot.
An IBM Token-Ring Network RT PC Adapter with the address
range 11CO - 11CF can
slot 5 of Model 10.
Section 6. Communication and Network Adapter Options 6-31
be installed in slot 8 of Model 25 or in
not