diff --git a/PDP10/kx10_dpy.c b/PDP10/kx10_dpy.c
index e8b3822..54e2fd6 100644
--- a/PDP10/kx10_dpy.c
+++ b/PDP10/kx10_dpy.c
@@ -246,6 +246,8 @@ t_stat dpy_devio(uint32 dev, uint64 *data) {
             dpy_update_status( uptr, ty340_reset(&dpy_dev), 1);
         sim_debug(DEBUG_CONO, &dpy_dev, "DPY %03o CONO %06o PC=%06o %06o\n",
                   dev, (uint32)*data, PC, uptr->STAT_REG & ~STAT_VALID);
+        if (!sim_is_active(uptr))
+            sim_activate_after(uptr, DPY_CYCLE_US);
         break;
 
     case DATAO:
@@ -262,6 +264,8 @@ t_stat dpy_devio(uint32 dev, uint64 *data) {
             inst = (uint32)RRZ(*data);
             dpy_update_status(uptr, ty340_instruction(inst), 1);
         }
+        if (!sim_is_active(uptr))
+            sim_activate_after(uptr, DPY_CYCLE_US);
         break;
 
     case DATAI:
@@ -276,7 +280,8 @@ t_stat dpy_devio(uint32 dev, uint64 *data) {
 /* Timer service - */
 t_stat dpy_svc (UNIT *uptr)
 {
-    sim_activate_after(uptr, DPY_CYCLE_US); /* requeue! */
+    if (!display_is_blank() || uptr->INT_COUNTDOWN > 0)
+        sim_activate_after(uptr, DPY_CYCLE_US); /* requeue! */
 
     display_age(DPY_CYCLE_US, 0);       /* age the display */
 
diff --git a/display/display.c b/display/display.c
index 94bf86c..5ad0691 100644
--- a/display/display.c
+++ b/display/display.c
@@ -439,6 +439,15 @@ queue_point(struct point *p)
     p->delay = d;
 }
 
+/*
+ * Return true if the display is blank, i.e. no active points in list.
+ */
+int
+display_is_blank(void)
+{
+    return head->next == head;
+}
+
 /*
  * here to to dynamically adjust interval for examination
  * of elapsed vs. simulated time, and fritter away
diff --git a/display/display.h b/display/display.h
index 0470f46..391bf4e 100644
--- a/display/display.h
+++ b/display/display.h
@@ -83,6 +83,11 @@ extern int display_scale(void);
  */
 extern int display_age(int,int);
 
+/*
+ * Return true if the display is blank.
+ */
+extern int display_is_blank(void);
+
 /*
  * display intensity levels.
  * always at least 8 (for VT11/VS60) -- may be mapped internally