diff --git a/sys/amd64/amd64/tsc.c b/sys/amd64/amd64/tsc.c
index 9467e2d9f4ab..dc02dea82ccc 100644
--- a/sys/amd64/amd64/tsc.c
+++ b/sys/amd64/amd64/tsc.c
@@ -34,7 +34,7 @@
  * SUCH DAMAGE.
  *
  *	from: @(#)clock.c	7.2 (Berkeley) 5/12/91
- *	$Id: clock.c,v 1.130 1999/04/21 07:26:27 peter Exp $
+ *	$Id: clock.c,v 1.131 1999/04/21 07:41:40 peter Exp $
  */
 
 /*
@@ -1115,6 +1115,7 @@ sysctl_machdep_i8254_freq SYSCTL_HANDLER_ARGS
 			return (EBUSY);	/* too much trouble to handle */
 		set_timer_freq(freq, hz);
 		i8254_timecounter.tc_frequency = freq;
+		update_timecounter(&i8254_timecounter);
 	}
 	return (error);
 }
@@ -1135,6 +1136,7 @@ sysctl_machdep_tsc_freq SYSCTL_HANDLER_ARGS
 	if (error == 0 && req->newptr != NULL) {
 		tsc_freq = freq;
 		tsc_timecounter.tc_frequency = tsc_freq;
+		update_timecounter(&tsc_timecounter);
 	}
 	return (error);
 }
diff --git a/sys/amd64/isa/clock.c b/sys/amd64/isa/clock.c
index 9467e2d9f4ab..dc02dea82ccc 100644
--- a/sys/amd64/isa/clock.c
+++ b/sys/amd64/isa/clock.c
@@ -34,7 +34,7 @@
  * SUCH DAMAGE.
  *
  *	from: @(#)clock.c	7.2 (Berkeley) 5/12/91
- *	$Id: clock.c,v 1.130 1999/04/21 07:26:27 peter Exp $
+ *	$Id: clock.c,v 1.131 1999/04/21 07:41:40 peter Exp $
  */
 
 /*
@@ -1115,6 +1115,7 @@ sysctl_machdep_i8254_freq SYSCTL_HANDLER_ARGS
 			return (EBUSY);	/* too much trouble to handle */
 		set_timer_freq(freq, hz);
 		i8254_timecounter.tc_frequency = freq;
+		update_timecounter(&i8254_timecounter);
 	}
 	return (error);
 }
@@ -1135,6 +1136,7 @@ sysctl_machdep_tsc_freq SYSCTL_HANDLER_ARGS
 	if (error == 0 && req->newptr != NULL) {
 		tsc_freq = freq;
 		tsc_timecounter.tc_frequency = tsc_freq;
+		update_timecounter(&tsc_timecounter);
 	}
 	return (error);
 }
diff --git a/sys/i386/i386/tsc.c b/sys/i386/i386/tsc.c
index 9467e2d9f4ab..dc02dea82ccc 100644
--- a/sys/i386/i386/tsc.c
+++ b/sys/i386/i386/tsc.c
@@ -34,7 +34,7 @@
  * SUCH DAMAGE.
  *
  *	from: @(#)clock.c	7.2 (Berkeley) 5/12/91
- *	$Id: clock.c,v 1.130 1999/04/21 07:26:27 peter Exp $
+ *	$Id: clock.c,v 1.131 1999/04/21 07:41:40 peter Exp $
  */
 
 /*
@@ -1115,6 +1115,7 @@ sysctl_machdep_i8254_freq SYSCTL_HANDLER_ARGS
 			return (EBUSY);	/* too much trouble to handle */
 		set_timer_freq(freq, hz);
 		i8254_timecounter.tc_frequency = freq;
+		update_timecounter(&i8254_timecounter);
 	}
 	return (error);
 }
@@ -1135,6 +1136,7 @@ sysctl_machdep_tsc_freq SYSCTL_HANDLER_ARGS
 	if (error == 0 && req->newptr != NULL) {
 		tsc_freq = freq;
 		tsc_timecounter.tc_frequency = tsc_freq;
+		update_timecounter(&tsc_timecounter);
 	}
 	return (error);
 }
diff --git a/sys/i386/isa/clock.c b/sys/i386/isa/clock.c
index 9467e2d9f4ab..dc02dea82ccc 100644
--- a/sys/i386/isa/clock.c
+++ b/sys/i386/isa/clock.c
@@ -34,7 +34,7 @@
  * SUCH DAMAGE.
  *
  *	from: @(#)clock.c	7.2 (Berkeley) 5/12/91
- *	$Id: clock.c,v 1.130 1999/04/21 07:26:27 peter Exp $
+ *	$Id: clock.c,v 1.131 1999/04/21 07:41:40 peter Exp $
  */
 
 /*
@@ -1115,6 +1115,7 @@ sysctl_machdep_i8254_freq SYSCTL_HANDLER_ARGS
 			return (EBUSY);	/* too much trouble to handle */
 		set_timer_freq(freq, hz);
 		i8254_timecounter.tc_frequency = freq;
+		update_timecounter(&i8254_timecounter);
 	}
 	return (error);
 }
@@ -1135,6 +1136,7 @@ sysctl_machdep_tsc_freq SYSCTL_HANDLER_ARGS
 	if (error == 0 && req->newptr != NULL) {
 		tsc_freq = freq;
 		tsc_timecounter.tc_frequency = tsc_freq;
+		update_timecounter(&tsc_timecounter);
 	}
 	return (error);
 }
diff --git a/sys/isa/atrtc.c b/sys/isa/atrtc.c
index 9467e2d9f4ab..dc02dea82ccc 100644
--- a/sys/isa/atrtc.c
+++ b/sys/isa/atrtc.c
@@ -34,7 +34,7 @@
  * SUCH DAMAGE.
  *
  *	from: @(#)clock.c	7.2 (Berkeley) 5/12/91
- *	$Id: clock.c,v 1.130 1999/04/21 07:26:27 peter Exp $
+ *	$Id: clock.c,v 1.131 1999/04/21 07:41:40 peter Exp $
  */
 
 /*
@@ -1115,6 +1115,7 @@ sysctl_machdep_i8254_freq SYSCTL_HANDLER_ARGS
 			return (EBUSY);	/* too much trouble to handle */
 		set_timer_freq(freq, hz);
 		i8254_timecounter.tc_frequency = freq;
+		update_timecounter(&i8254_timecounter);
 	}
 	return (error);
 }
@@ -1135,6 +1136,7 @@ sysctl_machdep_tsc_freq SYSCTL_HANDLER_ARGS
 	if (error == 0 && req->newptr != NULL) {
 		tsc_freq = freq;
 		tsc_timecounter.tc_frequency = tsc_freq;
+		update_timecounter(&tsc_timecounter);
 	}
 	return (error);
 }
diff --git a/sys/kern/kern_clock.c b/sys/kern/kern_clock.c
index 114a5926a0f3..a1b7727d3885 100644
--- a/sys/kern/kern_clock.c
+++ b/sys/kern/kern_clock.c
@@ -37,7 +37,7 @@
  * SUCH DAMAGE.
  *
  *	@(#)kern_clock.c	8.5 (Berkeley) 1/21/94
- * $Id: kern_clock.c,v 1.92 1999/03/12 21:58:54 phk Exp $
+ * $Id: kern_clock.c,v 1.93 1999/04/02 13:57:21 phk Exp $
  */
 
 #include "opt_ntp.h"
@@ -656,12 +656,18 @@ tco_setscales(struct timecounter *tc)
 
 	scale = 1000000000LL << 32;
 	scale += tc->tc_adjustment;
-	scale /= tc->tc_frequency;
+	scale /= tc->tc_tweak->tc_frequency;
 	tc->tc_scale_micro = scale / 1000;
 	tc->tc_scale_nano_f = scale & 0xffffffff;
 	tc->tc_scale_nano_i = scale >> 32;
 }
 
+void
+update_timecounter(struct timecounter *tc)
+{
+	tco_setscales(tc);
+}
+
 void
 init_timecounter(struct timecounter *tc)
 {
@@ -670,9 +676,9 @@ init_timecounter(struct timecounter *tc)
 	int i;
 
 	tc->tc_adjustment = 0;
+	tc->tc_tweak = tc;
 	tco_setscales(tc);
 	tc->tc_offset_count = tc->tc_get_timecount(tc);
-	tc->tc_tweak = tc;
 	MALLOC(t1, struct timecounter *, sizeof *t1, M_TIMECOUNTER, M_WAITOK);
 	*t1 = *tc;
 	t2 = t1;
diff --git a/sys/kern/kern_tc.c b/sys/kern/kern_tc.c
index 114a5926a0f3..a1b7727d3885 100644
--- a/sys/kern/kern_tc.c
+++ b/sys/kern/kern_tc.c
@@ -37,7 +37,7 @@
  * SUCH DAMAGE.
  *
  *	@(#)kern_clock.c	8.5 (Berkeley) 1/21/94
- * $Id: kern_clock.c,v 1.92 1999/03/12 21:58:54 phk Exp $
+ * $Id: kern_clock.c,v 1.93 1999/04/02 13:57:21 phk Exp $
  */
 
 #include "opt_ntp.h"
@@ -656,12 +656,18 @@ tco_setscales(struct timecounter *tc)
 
 	scale = 1000000000LL << 32;
 	scale += tc->tc_adjustment;
-	scale /= tc->tc_frequency;
+	scale /= tc->tc_tweak->tc_frequency;
 	tc->tc_scale_micro = scale / 1000;
 	tc->tc_scale_nano_f = scale & 0xffffffff;
 	tc->tc_scale_nano_i = scale >> 32;
 }
 
+void
+update_timecounter(struct timecounter *tc)
+{
+	tco_setscales(tc);
+}
+
 void
 init_timecounter(struct timecounter *tc)
 {
@@ -670,9 +676,9 @@ init_timecounter(struct timecounter *tc)
 	int i;
 
 	tc->tc_adjustment = 0;
+	tc->tc_tweak = tc;
 	tco_setscales(tc);
 	tc->tc_offset_count = tc->tc_get_timecount(tc);
-	tc->tc_tweak = tc;
 	MALLOC(t1, struct timecounter *, sizeof *t1, M_TIMECOUNTER, M_WAITOK);
 	*t1 = *tc;
 	t2 = t1;
diff --git a/sys/sys/time.h b/sys/sys/time.h
index 712fffe12fa5..43821b638edd 100644
--- a/sys/sys/time.h
+++ b/sys/sys/time.h
@@ -31,7 +31,7 @@
  * SUCH DAMAGE.
  *
  *	@(#)time.h	8.5 (Berkeley) 5/4/95
- * $Id: time.h,v 1.36 1999/03/08 12:36:14 phk Exp $
+ * $Id: time.h,v 1.37 1999/03/11 15:09:41 phk Exp $
  */
 
 #ifndef _SYS_TIME_H_
@@ -280,6 +280,7 @@ void	set_timecounter __P((struct timespec *ts));
 void	timevaladd __P((struct timeval *, struct timeval *));
 void	timevalsub __P((struct timeval *, struct timeval *));
 int	tvtohz __P((struct timeval *));
+void	update_timecounter __P((struct timecounter *tc));
 #else /* !KERNEL */
 #include <time.h>
 
diff --git a/sys/sys/timetc.h b/sys/sys/timetc.h
index 712fffe12fa5..43821b638edd 100644
--- a/sys/sys/timetc.h
+++ b/sys/sys/timetc.h
@@ -31,7 +31,7 @@
  * SUCH DAMAGE.
  *
  *	@(#)time.h	8.5 (Berkeley) 5/4/95
- * $Id: time.h,v 1.36 1999/03/08 12:36:14 phk Exp $
+ * $Id: time.h,v 1.37 1999/03/11 15:09:41 phk Exp $
  */
 
 #ifndef _SYS_TIME_H_
@@ -280,6 +280,7 @@ void	set_timecounter __P((struct timespec *ts));
 void	timevaladd __P((struct timeval *, struct timeval *));
 void	timevalsub __P((struct timeval *, struct timeval *));
 int	tvtohz __P((struct timeval *));
+void	update_timecounter __P((struct timecounter *tc));
 #else /* !KERNEL */
 #include <time.h>