IBM RT User's Setup Manual page 298

The jumpers on this adapter can be set to either interrupt level 3
or 9. If you have the IBM PC En han ced Graphics Adapter or the
IBM Personal Computer 3278/79 Emulation Adapter, ensure that
the interru pt level on the IBM PC Network Adapter is set to 3,
since these other two adapters use 9. To set the interrupt level to
3, set jumper W4 as shown. To set the interr upt level to 9, set the
same jumper (called W3 when set at 9) as shown in the illustration
below.
Note:
See
I n s t a l l i n g a n d C u s t o m i z i n g th e A I X O pera ting S y s te m
for additional information about inter rup t conflicts. Also see
"Adapter Conflicts" on page 1-19.
Installing:
You can install this adapter in slots 2 through 8 in
IBM 6150 and in slots 1 through 5 in IBM 6151, whichever is
available. See the system unit diagram for the correct adapter slot.
In IBM 6151, you can more easily connect cables if you install the
adapter in a slot other tha n adapter slot 1.
Section 6. Co mmunication and Network Adapter Options
W4 Interrupt Level 3
6-11