diff --git a/PDP10/ka10_iii.c b/PDP10/ka10_iii.c
index b132e3ee..89b29cec 100644
--- a/PDP10/ka10_iii.c
+++ b/PDP10/ka10_iii.c
@@ -40,6 +40,7 @@
 #define MAR               u4
 #define PIA               u5
 #define POS               u6
+#define CYCLE             us9
 
 /* CONO Bits */
 #define SET_PIA    000000010    /* Set if this bit is zero */
@@ -307,7 +308,7 @@ const char *iii_description (DEVICE *dptr);
 DIB iii_dib = { III_DEVNUM, 1, iii_devio, NULL};
 
 UNIT iii_unit[] = {
-    {UDATA (&iii_svc, UNIT_IDLE, 0) },
+    {UDATA (&iii_svc, 0, 0) },
     { 0 }
     };
 
@@ -396,7 +397,12 @@ iii_svc (UNIT *uptr)
      int       i, j, ch;
      float     ch_sz;
 
-     iii_cycle(10, 0);
+     if (uptr->CYCLE > 20) {
+         iii_cycle(300, 0);
+         uptr->CYCLE = 0;
+     } else {
+         uptr->CYCLE++;
+     }
 
      /* Extract X,Y,Bright and Size */
      sz = (uptr->POS & CSIZE) >> CSIZE_V;
@@ -615,7 +621,7 @@ skip_up:
                       uptr->MAR, iii_instr);
          uptr->MAR++;
          uptr->MAR &= RMASK;
-         sim_activate(uptr, 50);
+         sim_activate_after(uptr, 60);
      }
 
      if (((uptr->STATUS >> 3) & (uptr->STATUS & (WRAP_MSK|EDGE_MSK|LIGH_MSK))) != 0)
diff --git a/PDP10/ka10_pmp.c b/PDP10/ka10_pmp.c
index 96891b38..828decaf 100644
--- a/PDP10/ka10_pmp.c
+++ b/PDP10/ka10_pmp.c
@@ -1407,7 +1407,7 @@ sense_end:
          sim_debug(DEBUG_DETAIL, dptr, "seek unit=%d %d %d\n", unit, trk, buf[5]);
 
          /* Check if seek valid */
-         if ((buf[0] | buf[1] | buf[4]) != 0 || trk > disk_type[type].cyl
+         if ((buf[0] | buf[1] | buf[4]) != 0 || trk >= disk_type[type].cyl
                   || buf[5] >= disk_type[type].heads)  {
              uptr->LASTCMD = cmd;
              uptr->CMD &= ~(0xff);
@@ -2161,7 +2161,7 @@ pmp_format(UNIT * uptr, int flag) {
         data->tsize = hdr.tracksize;
         if ((data->cbuf = (uint8 *)calloc(tsize, sizeof(uint8))) == 0)
             return 1;
-        for (cyl = 0; cyl <= disk_type[type].cyl; cyl++) {
+        for (cyl = 0; cyl < disk_type[type].cyl; cyl++) {
             pos = 0;
             for (hd = 0; hd < disk_type[type].heads; hd++) {
                 uint32 cpos = pos;