Someone with an SS1 or SS1+ might want to try this....

Index: sbus.c
===================================================================
RCS file: /cvsroot/src/sys/arch/sparc/dev/sbus.c,v
retrieving revision 1.17
diff -c -r1.17 sbus.c
*** sbus.c      1997/06/01 22:10:39     1.17
--- sbus.c      1998/10/16 22:26:05
***************
*** 85,94 ****
--- 85,97 ----
        void *args;
        const char *sbus;
  {
+       static char *sl = "slave-only";
        register struct confargs *ca = args;
  
        if (sbus)
                printf("%s at %s", ca->ca_ra.ra_name, sbus);
+       if (getpropint(ca->ca_ra.ra_node, sl, 0))
+               printf(" %s", sl);
        printf(" slot %d offset 0x%x", ca->ca_slot, ca->ca_offset);
        return (UNCONF);
  }