diff --git a/B5500/b5500_cpu.c b/B5500/b5500_cpu.c
index 472ac088..6199afc3 100644
--- a/B5500/b5500_cpu.c
+++ b/B5500/b5500_cpu.c
@@ -2001,6 +2001,7 @@ sim_instr(void)
             reason = sim_process_event();
             if (reason != SCPE_OK)
                  break; /* process */
+            sim_interval--;
         }
         /* Passed time quantum */
         if (sim_interval <= 0) {        /* event queue? */
diff --git a/B5500/b5500_dk.c b/B5500/b5500_dk.c
index 84b12049..afff3762 100644
--- a/B5500/b5500_dk.c
+++ b/B5500/b5500_dk.c
@@ -188,7 +188,7 @@ t_stat dsk_cmd(uint16 cmd, uint16 dev, uint8 chan, uint16 *wc)
     } else {
         uptr->CMD |= DK_ADDR;
     }
-    sim_activate(uptr, 100);
+    sim_activate(uptr, 90);
     return SCPE_OK;
 }
         
@@ -292,7 +292,7 @@ t_stat dsk_srv(UNIT * uptr)
             sim_activate(eptr, 8000);
             return SCPE_OK;
         }
-        sim_activate(uptr, 100);
+        sim_activate(uptr, 90);
     }
     return SCPE_OK;
 }