diff --git a/PDP10/pdp10_cpu.c b/PDP10/pdp10_cpu.c
index 34dd92d1..af508f79 100644
--- a/PDP10/pdp10_cpu.c
+++ b/PDP10/pdp10_cpu.c
@@ -2358,6 +2358,10 @@ static const char *pdp10_clock_precalibrate_commands[] = {
     "PC 100",
     NULL};
 
+static const char *pdp10_clock_precalibrate_cleanup_commands[] = {
+    "0-120 0",
+    NULL};
+
 /* Reset routine */
 
 t_stat cpu_reset (DEVICE *dptr)
@@ -2380,6 +2384,7 @@ if (M == NULL)
 sim_vm_pc_value = &pdp10_pc_value;
 sim_vm_is_subroutine_call = &cpu_is_pc_a_subroutine_call;
 sim_clock_precalibrate_commands = pdp10_clock_precalibrate_commands;
+sim_clock_precalibrate_cleanup_commands = pdp10_clock_precalibrate_cleanup_commands;
 sim_vm_initial_ips = 2 * SIM_INITIAL_IPS;
 pcq_r = find_reg ("PCQ", NULL, dptr);
 if (pcq_r)
diff --git a/PDP11/pdp11_cpu.c b/PDP11/pdp11_cpu.c
index 63359927..3cb280c1 100644
--- a/PDP11/pdp11_cpu.c
+++ b/PDP11/pdp11_cpu.c
@@ -3413,6 +3413,10 @@ static const char *pdp11_clock_precalibrate_commands[] = {
     "PC 100",
     NULL};
 
+static const char *pdp11_clock_precalibrate_cleanup_commands[] = {
+    "100-200 0",
+    NULL};
+
 /* Special boot command - linked into SCP by initial reset
 
    Syntax: BOOT {CPU}
@@ -3480,6 +3484,7 @@ if (M == NULL) {                    /* First time init */
     sim_brk_type_desc = cpu_breakpoints;
     sim_vm_is_subroutine_call = &cpu_is_pc_a_subroutine_call;
     sim_clock_precalibrate_commands = pdp11_clock_precalibrate_commands;
+    sim_clock_precalibrate_cleanup_commands = pdp11_clock_precalibrate_cleanup_commands;
     auto_config(NULL, 0);           /* do an initial auto configure */
     }
 pcq_r = find_reg ("PCQ", NULL, dptr);
diff --git a/PDP8/pdp8_cpu.c b/PDP8/pdp8_cpu.c
index 35ab239b..3abf4c26 100644
--- a/PDP8/pdp8_cpu.c
+++ b/PDP8/pdp8_cpu.c
@@ -1387,6 +1387,10 @@ static const char *pdp8_clock_precalibrate_commands[] = {
     "PC 100",
     NULL};
 
+static const char *pdp8_clock_precalibrate_cleanup_commands[] = {
+    "100-112 0",
+    NULL};
+
 /* Reset routine */
 
 t_stat cpu_reset (DEVICE *dptr)
@@ -1401,6 +1405,7 @@ if (pcq_r)
 else 
     return SCPE_IERR;
 sim_clock_precalibrate_commands = pdp8_clock_precalibrate_commands;
+sim_clock_precalibrate_cleanup_commands = pdp8_clock_precalibrate_cleanup_commands;
 sim_vm_initial_ips = 10 * SIM_INITIAL_IPS;
 sim_brk_types = SWMASK ('E') | SWMASK('I');
 sim_brk_dflt = SWMASK ('E');
diff --git a/SDS/sds_cpu.c b/SDS/sds_cpu.c
index 103691cd..8d525dda 100644
--- a/SDS/sds_cpu.c
+++ b/SDS/sds_cpu.c
@@ -1806,12 +1806,17 @@ static const char *sds_clock_precalibrate_commands[] = {
     "111 BRU 100",
     NULL};
 
+static const char *sds_clock_precalibrate_cleanup_commands[] = {
+    "100-120 0",
+    NULL};
+
 
 /* Clock reset */
 
 t_stat rtc_reset (DEVICE *dptr)
 {
 sim_clock_precalibrate_commands = sds_clock_precalibrate_commands;
+sim_clock_precalibrate_cleanup_commands = sds_clock_precalibrate_cleanup_commands;
 rtc_pie = 0;                                            /* disable pulse */
 rtc_unit.wait = sim_rtcn_init (rtc_unit.wait, TMR_RTC); /* initialize clock calibration */
 sim_activate (&rtc_unit, rtc_unit.wait);                /* activate unit */
diff --git a/VAX/vax_cpu.c b/VAX/vax_cpu.c
index b9a2a49b..37ddc2f3 100644
--- a/VAX/vax_cpu.c
+++ b/VAX/vax_cpu.c
@@ -3324,6 +3324,10 @@ static const char *vax_clock_precalibrate_commands[] = {
     "PC 100",
     NULL};
 
+static const char *vax_clock_precalibrate_cleanup_commands[] = {
+    "100-140 0",
+    NULL};
+
 /* Reset */
 
 t_stat cpu_reset (DEVICE *dptr)
@@ -3341,6 +3345,7 @@ if (M == NULL) {                        /* first time init? */
     sim_brk_types = sim_brk_dflt = SWMASK ('E');
     sim_vm_is_subroutine_call = cpu_is_pc_a_subroutine_call;
     sim_clock_precalibrate_commands = vax_clock_precalibrate_commands;
+    sim_clock_precalibrate_cleanup_commands = vax_clock_precalibrate_cleanup_commands;
     sim_vm_initial_ips = SIM_INITIAL_IPS;
     pcq_r = find_reg ("PCQ", NULL, dptr);
     if (pcq_r == NULL)
diff --git a/doc/simh.doc b/doc/simh.doc
index 9f6dd638..244ddc2a 100644
Binary files a/doc/simh.doc and b/doc/simh.doc differ
diff --git a/scp.c b/scp.c
index 168b7829..70595633 100644
--- a/scp.c
+++ b/scp.c
@@ -483,6 +483,7 @@ t_bool (*sim_vm_fprint_stopped) (FILE *st, t_stat reason) = NULL;
 const char *sim_vm_release = NULL;
 const char *sim_vm_release_message = NULL;
 const char **sim_clock_precalibrate_commands = NULL;
+const char **sim_clock_precalibrate_cleanup_commands = NULL;
 
 
 /* Prototypes */
diff --git a/scp.h b/scp.h
index b7ee0b5f..52a8be39 100644
--- a/scp.h
+++ b/scp.h
@@ -391,6 +391,7 @@ extern t_value (*sim_vm_pc_value) (void);
 extern t_bool (*sim_vm_is_subroutine_call) (t_addr **ret_addrs);
 extern void (*sim_vm_reg_update) (REG *rptr, uint32 idx, t_value prev_val, t_value new_val);
 extern const char **sim_clock_precalibrate_commands;
+extern const char **sim_clock_precalibrate_cleanup_commands;
 extern uint32 sim_vm_initial_ips;                       /* base estimate of simulated instructions per second */
 extern const char *sim_vm_interval_units;               /* Simulator can change this - default "instructions" */
 extern const char *sim_vm_step_unit;                    /* Simulator can change this - default "instruction" */
diff --git a/sim_timer.c b/sim_timer.c
index 5676dde9..a5aa0e70 100644
--- a/sim_timer.c
+++ b/sim_timer.c
@@ -3820,6 +3820,10 @@ for (tmr=0; tmr<=SIM_NTIMERS; tmr++) {
     if (rtc->hz)
         rtc->initd = rtc->currd = (int32)(((double)sim_precalibrate_ips) / rtc->hz);
     }
+if ((cmd = sim_clock_precalibrate_cleanup_commands)) {
+    while (*cmd)
+         exdep_cmd (EX_D, *(cmd++));
+    }
 reset_all_p (0);
 sim_run_boot_prep (RU_GO);
 for (tmr=0; tmr<=SIM_NTIMERS; tmr++) {