diff --git a/PDP11/pdp11_defs.h b/PDP11/pdp11_defs.h
index be96c3cf..cd22da38 100644
--- a/PDP11/pdp11_defs.h
+++ b/PDP11/pdp11_defs.h
@@ -512,7 +512,9 @@ struct pdp_dib {
     int32               vloc;                           /* locator */
     int32               vec;                            /* value */
     int32               (*ack[VEC_DEVMAX])(void);       /* ack routines */
-    uint32             ulnt;                            /* IO length per-unit */
+    uint32              ulnt;                           /* IO length per-device */
+                                                        /* Only need to be populated */
+                                                        /* when numunits != num devices */
     };
 
 typedef struct pdp_dib DIB;
diff --git a/PDP11/pdp11_dl.c b/PDP11/pdp11_dl.c
index f13a0813..5b04f420 100644
--- a/PDP11/pdp11_dl.c
+++ b/PDP11/pdp11_dl.c
@@ -160,7 +160,7 @@ DEVICE dli_dev = {
     1, 10, 31, 1, 8, 8,
     NULL, NULL, &dlx_reset,
     NULL, &dlx_attach, &dlx_detach,
-    &dli_dib, DEV_UBUS | DEV_QBUS | DEV_DISABLE | DEV_DIS
+    &dli_dib, DEV_UBUS | DEV_QBUS | DEV_DISABLE | DEV_DIS | DEV_MUX
     };
 
 /* DLO data structures
@@ -219,7 +219,7 @@ DEVICE dlo_dev = {
     DLX_LINES, 10, 31, 1, 8, 8,
     NULL, NULL, &dlx_reset,
     NULL, NULL, NULL,
-    NULL, DEV_UBUS | DEV_QBUS | DEV_DISABLE | DEV_DIS | DEV_MUX
+    NULL, DEV_UBUS | DEV_QBUS | DEV_DISABLE | DEV_DIS
     };
 
 /* Terminal input routines */
diff --git a/PDP11/pdp11_rh.c b/PDP11/pdp11_rh.c
index a7c4e8fa..2fe4f17f 100644
--- a/PDP11/pdp11_rh.c
+++ b/PDP11/pdp11_rh.c
@@ -245,7 +245,7 @@ MTAB mba0_mod[] = {
 
 DIB mba1_dib = {
     IOBA_AUTO, IOLN_TU, &mba_rd, &mba_wr,
-    1, IVCL (TU), VEC_AUTO, { &mba1_inta }
+    1, IVCL (TU), VEC_AUTO, { &mba1_inta }, IOLN_TU
     };
 
 UNIT mba1_unit = { UDATA (NULL, 0, 0) };
@@ -280,7 +280,7 @@ MTAB mba1_mod[] = {
 
 DIB mba2_dib = {
     IOBA_AUTO, IOLN_RS, &mba_rd, &mba_wr,
-    1, IVCL (RS), VEC_AUTO, { &mba2_inta }
+    1, IVCL (RS), VEC_AUTO, { &mba2_inta }, IOLN_RS
     };
 
 UNIT mba2_unit = { UDATA (NULL, 0, 0) };
diff --git a/PDP11/pdp11_rq.c b/PDP11/pdp11_rq.c
index 04bfc00f..7bef0a40 100644
--- a/PDP11/pdp11_rq.c
+++ b/PDP11/pdp11_rq.c
@@ -1028,7 +1028,7 @@ MSC rqb_ctx = { 1 };
 
 DIB rqb_dib = {
     IOBA_AUTO, IOLN_RQ, &rq_rd, &rq_wr,
-    1, IVCL (RQ), 0, { &rq_inta }
+    1, IVCL (RQ), 0, { &rq_inta }, IOLN_RQ
     };
 
 UNIT rqb_unit[] = {
@@ -1103,7 +1103,7 @@ MSC rqc_ctx = { 2 };
 
 DIB rqc_dib = {
     IOBA_AUTO, IOLN_RQ, &rq_rd, &rq_wr,
-    1, IVCL (RQ), 0, { &rq_inta }
+    1, IVCL (RQ), 0, { &rq_inta }, IOLN_RQ
     };
 
 UNIT rqc_unit[] = {
@@ -1178,7 +1178,7 @@ MSC rqd_ctx = { 3 };
 
 DIB rqd_dib = {
     IOBA_AUTO, IOLN_RQ, &rq_rd, &rq_wr,
-    1, IVCL (RQ), 0, { &rq_inta }
+    1, IVCL (RQ), 0, { &rq_inta }, IOLN_RQ
     };
 
 UNIT rqd_unit[] = {
diff --git a/PDP11/pdp11_xq.c b/PDP11/pdp11_xq.c
index 5c679bc3..f285c5c1 100644
--- a/PDP11/pdp11_xq.c
+++ b/PDP11/pdp11_xq.c
@@ -400,7 +400,7 @@ REG xqa_reg[] = {
 };
 
 DIB xqb_dib = { IOBA_AUTO, IOLN_XQ, &xq_rd, &xq_wr,
-        1, IVCL (XQ), 0, { &xq_int } };
+                1, IVCL (XQ), 0, { &xq_int }, IOLN_XQ };
 
 UNIT xqb_unit[] = {
  { UDATA (&xq_svc, UNIT_IDLE|UNIT_ATTABLE|UNIT_DISABLE, 2047) },  /* receive timer */
diff --git a/PDP11/pdp11_xu.c b/PDP11/pdp11_xu.c
index 76fb3f1e..87fa78a0 100644
--- a/PDP11/pdp11_xu.c
+++ b/PDP11/pdp11_xu.c
@@ -134,7 +134,7 @@ char *xu_description (DEVICE *dptr);
 #define IOLN_XU        010
 
 DIB xua_dib = { IOBA_AUTO, IOLN_XU, &xu_rd, &xu_wr,
-1, IVCL (XU), VEC_AUTO, {&xu_int}, IOLN_XU };
+                1, IVCL (XU), VEC_AUTO, {&xu_int}, IOLN_XU };
 
 UNIT xua_unit[] = {
  { UDATA (&xu_svc, UNIT_IDLE|UNIT_ATTABLE|UNIT_DISABLE, 0) },     /* receive timer */
@@ -231,10 +231,8 @@ DEVICE xu_dev = {
     &xu_description
   };
 
-#define IOLN_XU         010
-
 DIB xub_dib = { IOBA_AUTO, IOLN_XU, &xu_rd, &xu_wr,
-        1, IVCL (XU), 0, { &xu_int }, IOLN_XU };
+                1, IVCL (XU), 0, { &xu_int }, IOLN_XU };
 
 UNIT xub_unit[] = {
  { UDATA (&xu_svc, UNIT_IDLE|UNIT_ATTABLE|UNIT_DISABLE, 0) }      /* receive timer */