IBM RT PC Options Installation page 179

Installing: You can install this adapter in slots 2, 4, 5, 7, and
8 in 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
11C0 - 11CF can not be installed in slot 8 of Model 25 or in slot 5 of
Model 10.
Section 6. Communication and Network Adapter Options 6-31