7 files changed, 217 insertions, 94 deletions

diff --git a/sys/amd64/amd64/tsc.c b/sys/amd64/amd64/tsc.c
index 58678a6ea3778..7257b2fb8226a 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 1.64 1996/07/20 18:47:23 joerg Exp $
+ *	$Id: clock.c,v 1.65 1996/07/21 08:20:51 joerg Exp $
  */
 
 /*
@@ -102,7 +102,9 @@ int	wall_cmos_clock;	/* wall	CMOS clock assumed if != 0 */
 
 u_int	idelayed;
 #if defined(I586_CPU) || defined(I686_CPU)
-unsigned	i586_ctr_freq;
+u_int	i586_ctr_comultiplier;
+u_int	i586_ctr_freq;
+u_int	i586_ctr_multiplier;
 unsigned	i586_ctr_rate;
 long long	i586_ctr_bias;
 long long	i586_last_tick;
@@ -144,6 +146,10 @@ static	u_char	timer0_state;
 static	u_char	timer2_state;
 static 	void	(*timer_func) __P((struct clockframe *frame)) = hardclock;
 
+#if defined(I586_CPU) || defined(I686_CPU)
+static	void	set_i586_ctr_freq(u_int i586_freq, u_int i8254_freq);
+#endif
+
 static void
 clkintr(struct clockframe frame)
 {
@@ -553,11 +559,7 @@ calibrate_clocks(void)
 	 * similar to those for the i8254 clock.
 	 */
 	if (cpu_class == CPUCLASS_586 || cpu_class == CPUCLASS_686) {
-		unsigned long long i586_count;
-
-		i586_count = rdtsc();
-		i586_ctr_freq = i586_count;
-		i586_ctr_rate = (i586_count << I586_CTR_RATE_SHIFT) / 1000000;
+		set_i586_ctr_freq((u_int)rdtsc(), tot_count);
 		printf("i586 clock: %u Hz, ", i586_ctr_freq);
 	}
 #endif
@@ -651,12 +653,9 @@ startrtclock()
 		 * clock failed.  Do a less accurate calibration relative
 		 * to the i8254 clock.
 		 */
-		unsigned long long i586_count;
-
 		wrmsr(0x10, 0LL);	/* XXX */
 		DELAY(1000000);
-		i586_count = rdtsc();
-		i586_ctr_rate = (i586_count << I586_CTR_RATE_SHIFT) / 1000000;
+		set_i586_ctr_freq((u_int)rdtsc(), timer_freq);
 #ifdef CLK_USE_I586_CALIBRATION
 		printf("i586 clock: %u Hz\n", i586_ctr_freq);
 #endif
@@ -861,10 +860,13 @@ sysctl_machdep_i8254_freq SYSCTL_HANDLER_ARGS
 	 */
 	freq = timer_freq;
 	error = sysctl_handle_opaque(oidp, &freq, sizeof freq, req);
-	if (error == 0 && freq != timer_freq) {
+	if (error == 0 && req->newptr != NULL) {
 		if (timer0_state != 0)
 			return (EBUSY);	/* too much trouble to handle */
 		set_timer_freq(freq, hz);
+#if defined(I586_CPU) || defined(I686_CPU)
+		set_i586_ctr_freq(i586_ctr_freq, timer_freq);
+#endif
 	}
 	return (error);
 }
@@ -873,21 +875,42 @@ SYSCTL_PROC(_machdep, OID_AUTO, i8254_freq, CTLTYPE_INT | CTLFLAG_RW,
 	    0, sizeof(u_int), sysctl_machdep_i8254_freq, "I", "");
 
 #if defined(I586_CPU) || defined(I686_CPU)
+static void
+set_i586_ctr_freq(u_int i586_freq, u_int i8254_freq)
+{
+	u_int comultiplier, multiplier, rate;
+	u_long ef;
+
+	if (i586_freq == 0) {
+		i586_ctr_freq = i586_freq;
+		i586_ctr_rate = 0;
+		return;
+	}
+	comultiplier = ((unsigned long long)i586_freq
+			<< I586_CTR_COMULTIPLIER_SHIFT) / i8254_freq;
+	multiplier = (1000000LL << I586_CTR_MULTIPLIER_SHIFT) / i586_freq;
+	rate = ((unsigned long long)i586_freq << I586_CTR_RATE_SHIFT) / 1000000;
+	ef = read_eflags();
+	disable_intr();
+	i586_ctr_freq = i586_freq;
+	i586_ctr_comultiplier = comultiplier;
+	i586_ctr_multiplier = multiplier;
+	i586_ctr_rate = rate;
+	write_eflags(ef);
+}
+
 static int
 sysctl_machdep_i586_freq SYSCTL_HANDLER_ARGS
 {
 	int error;
 	u_int freq;
 
-	if (i586_ctr_rate == 0)
+	if (cpu_class != CPUCLASS_586 && cpu_class != CPUCLASS_686)
 		return (EOPNOTSUPP);
 	freq = i586_ctr_freq;
 	error = sysctl_handle_opaque(oidp, &freq, sizeof freq, req);
-	if (error == 0 && freq != i586_ctr_freq) {
-		i586_ctr_freq = freq;
-		i586_ctr_rate = ((unsigned long long)freq <<
-				 I586_CTR_RATE_SHIFT) / 1000000;
-	}
+	if (error == 0 && req->newptr != NULL)
+		set_i586_ctr_freq(freq, timer_freq);
 	return (error);
 }
 
diff --git a/sys/amd64/include/clock.h b/sys/amd64/include/clock.h
index 830ae1367a08e..043936310dd5b 100644
--- a/sys/amd64/include/clock.h
+++ b/sys/amd64/include/clock.h
@@ -3,7 +3,7 @@
  * Garrett Wollman, September 1994.
  * This file is in the public domain.
  *
- *	$Id: clock.h,v 1.13 1996/05/01 08:38:50 bde Exp $
+ *	$Id: clock.h,v 1.14 1996/06/14 11:00:56 asami Exp $
  */
 
 #ifndef _MACHINE_CLOCK_H_
@@ -38,6 +38,8 @@
 #define CPU_THISTICKLEN(dflt) dflt
 #endif
 
+#define	I586_CTR_COMULTIPLIER_SHIFT	20
+#define	I586_CTR_MULTIPLIER_SHIFT	32
 #define		I586_CTR_RATE_SHIFT	8
 
 #if defined(KERNEL) && !defined(LOCORE)
@@ -55,7 +57,9 @@ extern int	statclock_disable;
 extern int	wall_cmos_clock;
 
 #if defined(I586_CPU) || defined(I686_CPU)
-extern unsigned	i586_ctr_freq;
+extern u_int	i586_ctr_comultiplier;
+extern u_int	i586_ctr_freq;
+extern u_int	i586_ctr_multiplier;
 extern unsigned	i586_ctr_rate;	/* fixed point */
 extern long long i586_last_tick;
 extern long long i586_ctr_bias;
diff --git a/sys/amd64/isa/clock.c b/sys/amd64/isa/clock.c
index 58678a6ea3778..7257b2fb8226a 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 1.64 1996/07/20 18:47:23 joerg Exp $
+ *	$Id: clock.c,v 1.65 1996/07/21 08:20:51 joerg Exp $
  */
 
 /*
@@ -102,7 +102,9 @@ int	wall_cmos_clock;	/* wall	CMOS clock assumed if != 0 */
 
 u_int	idelayed;
 #if defined(I586_CPU) || defined(I686_CPU)
-unsigned	i586_ctr_freq;
+u_int	i586_ctr_comultiplier;
+u_int	i586_ctr_freq;
+u_int	i586_ctr_multiplier;
 unsigned	i586_ctr_rate;
 long long	i586_ctr_bias;
 long long	i586_last_tick;
@@ -144,6 +146,10 @@ static	u_char	timer0_state;
 static	u_char	timer2_state;
 static 	void	(*timer_func) __P((struct clockframe *frame)) = hardclock;
 
+#if defined(I586_CPU) || defined(I686_CPU)
+static	void	set_i586_ctr_freq(u_int i586_freq, u_int i8254_freq);
+#endif
+
 static void
 clkintr(struct clockframe frame)
 {
@@ -553,11 +559,7 @@ calibrate_clocks(void)
 	 * similar to those for the i8254 clock.
 	 */
 	if (cpu_class == CPUCLASS_586 || cpu_class == CPUCLASS_686) {
-		unsigned long long i586_count;
-
-		i586_count = rdtsc();
-		i586_ctr_freq = i586_count;
-		i586_ctr_rate = (i586_count << I586_CTR_RATE_SHIFT) / 1000000;
+		set_i586_ctr_freq((u_int)rdtsc(), tot_count);
 		printf("i586 clock: %u Hz, ", i586_ctr_freq);
 	}
 #endif
@@ -651,12 +653,9 @@ startrtclock()
 		 * clock failed.  Do a less accurate calibration relative
 		 * to the i8254 clock.
 		 */
-		unsigned long long i586_count;
-
 		wrmsr(0x10, 0LL);	/* XXX */
 		DELAY(1000000);
-		i586_count = rdtsc();
-		i586_ctr_rate = (i586_count << I586_CTR_RATE_SHIFT) / 1000000;
+		set_i586_ctr_freq((u_int)rdtsc(), timer_freq);
 #ifdef CLK_USE_I586_CALIBRATION
 		printf("i586 clock: %u Hz\n", i586_ctr_freq);
 #endif
@@ -861,10 +860,13 @@ sysctl_machdep_i8254_freq SYSCTL_HANDLER_ARGS
 	 */
 	freq = timer_freq;
 	error = sysctl_handle_opaque(oidp, &freq, sizeof freq, req);
-	if (error == 0 && freq != timer_freq) {
+	if (error == 0 && req->newptr != NULL) {
 		if (timer0_state != 0)
 			return (EBUSY);	/* too much trouble to handle */
 		set_timer_freq(freq, hz);
+#if defined(I586_CPU) || defined(I686_CPU)
+		set_i586_ctr_freq(i586_ctr_freq, timer_freq);
+#endif
 	}
 	return (error);
 }
@@ -873,21 +875,42 @@ SYSCTL_PROC(_machdep, OID_AUTO, i8254_freq, CTLTYPE_INT | CTLFLAG_RW,
 	    0, sizeof(u_int), sysctl_machdep_i8254_freq, "I", "");
 
 #if defined(I586_CPU) || defined(I686_CPU)
+static void
+set_i586_ctr_freq(u_int i586_freq, u_int i8254_freq)
+{
+	u_int comultiplier, multiplier, rate;
+	u_long ef;
+
+	if (i586_freq == 0) {
+		i586_ctr_freq = i586_freq;
+		i586_ctr_rate = 0;
+		return;
+	}
+	comultiplier = ((unsigned long long)i586_freq
+			<< I586_CTR_COMULTIPLIER_SHIFT) / i8254_freq;
+	multiplier = (1000000LL << I586_CTR_MULTIPLIER_SHIFT) / i586_freq;
+	rate = ((unsigned long long)i586_freq << I586_CTR_RATE_SHIFT) / 1000000;
+	ef = read_eflags();
+	disable_intr();
+	i586_ctr_freq = i586_freq;
+	i586_ctr_comultiplier = comultiplier;
+	i586_ctr_multiplier = multiplier;
+	i586_ctr_rate = rate;
+	write_eflags(ef);
+}
+
 static int
 sysctl_machdep_i586_freq SYSCTL_HANDLER_ARGS
 {
 	int error;
 	u_int freq;
 
-	if (i586_ctr_rate == 0)
+	if (cpu_class != CPUCLASS_586 && cpu_class != CPUCLASS_686)
 		return (EOPNOTSUPP);
 	freq = i586_ctr_freq;
 	error = sysctl_handle_opaque(oidp, &freq, sizeof freq, req);
-	if (error == 0 && freq != i586_ctr_freq) {
-		i586_ctr_freq = freq;
-		i586_ctr_rate = ((unsigned long long)freq <<
-				 I586_CTR_RATE_SHIFT) / 1000000;
-	}
+	if (error == 0 && req->newptr != NULL)
+		set_i586_ctr_freq(freq, timer_freq);
 	return (error);
 }
 
diff --git a/sys/i386/i386/tsc.c b/sys/i386/i386/tsc.c
index 58678a6ea3778..7257b2fb8226a 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 1.64 1996/07/20 18:47:23 joerg Exp $
+ *	$Id: clock.c,v 1.65 1996/07/21 08:20:51 joerg Exp $
  */
 
 /*
@@ -102,7 +102,9 @@ int	wall_cmos_clock;	/* wall	CMOS clock assumed if != 0 */
 
 u_int	idelayed;
 #if defined(I586_CPU) || defined(I686_CPU)
-unsigned	i586_ctr_freq;
+u_int	i586_ctr_comultiplier;
+u_int	i586_ctr_freq;
+u_int	i586_ctr_multiplier;
 unsigned	i586_ctr_rate;
 long long	i586_ctr_bias;
 long long	i586_last_tick;
@@ -144,6 +146,10 @@ static	u_char	timer0_state;
 static	u_char	timer2_state;
 static 	void	(*timer_func) __P((struct clockframe *frame)) = hardclock;
 
+#if defined(I586_CPU) || defined(I686_CPU)
+static	void	set_i586_ctr_freq(u_int i586_freq, u_int i8254_freq);
+#endif
+
 static void
 clkintr(struct clockframe frame)
 {
@@ -553,11 +559,7 @@ calibrate_clocks(void)
 	 * similar to those for the i8254 clock.
 	 */
 	if (cpu_class == CPUCLASS_586 || cpu_class == CPUCLASS_686) {
-		unsigned long long i586_count;
-
-		i586_count = rdtsc();
-		i586_ctr_freq = i586_count;
-		i586_ctr_rate = (i586_count << I586_CTR_RATE_SHIFT) / 1000000;
+		set_i586_ctr_freq((u_int)rdtsc(), tot_count);
 		printf("i586 clock: %u Hz, ", i586_ctr_freq);
 	}
 #endif
@@ -651,12 +653,9 @@ startrtclock()
 		 * clock failed.  Do a less accurate calibration relative
 		 * to the i8254 clock.
 		 */
-		unsigned long long i586_count;
-
 		wrmsr(0x10, 0LL);	/* XXX */
 		DELAY(1000000);
-		i586_count = rdtsc();
-		i586_ctr_rate = (i586_count << I586_CTR_RATE_SHIFT) / 1000000;
+		set_i586_ctr_freq((u_int)rdtsc(), timer_freq);
 #ifdef CLK_USE_I586_CALIBRATION
 		printf("i586 clock: %u Hz\n", i586_ctr_freq);
 #endif
@@ -861,10 +860,13 @@ sysctl_machdep_i8254_freq SYSCTL_HANDLER_ARGS
 	 */
 	freq = timer_freq;
 	error = sysctl_handle_opaque(oidp, &freq, sizeof freq, req);
-	if (error == 0 && freq != timer_freq) {
+	if (error == 0 && req->newptr != NULL) {
 		if (timer0_state != 0)
 			return (EBUSY);	/* too much trouble to handle */
 		set_timer_freq(freq, hz);
+#if defined(I586_CPU) || defined(I686_CPU)
+		set_i586_ctr_freq(i586_ctr_freq, timer_freq);
+#endif
 	}
 	return (error);
 }
@@ -873,21 +875,42 @@ SYSCTL_PROC(_machdep, OID_AUTO, i8254_freq, CTLTYPE_INT | CTLFLAG_RW,
 	    0, sizeof(u_int), sysctl_machdep_i8254_freq, "I", "");
 
 #if defined(I586_CPU) || defined(I686_CPU)
+static void
+set_i586_ctr_freq(u_int i586_freq, u_int i8254_freq)
+{
+	u_int comultiplier, multiplier, rate;
+	u_long ef;
+
+	if (i586_freq == 0) {
+		i586_ctr_freq = i586_freq;
+		i586_ctr_rate = 0;
+		return;
+	}
+	comultiplier = ((unsigned long long)i586_freq
+			<< I586_CTR_COMULTIPLIER_SHIFT) / i8254_freq;
+	multiplier = (1000000LL << I586_CTR_MULTIPLIER_SHIFT) / i586_freq;
+	rate = ((unsigned long long)i586_freq << I586_CTR_RATE_SHIFT) / 1000000;
+	ef = read_eflags();
+	disable_intr();
+	i586_ctr_freq = i586_freq;
+	i586_ctr_comultiplier = comultiplier;
+	i586_ctr_multiplier = multiplier;
+	i586_ctr_rate = rate;
+	write_eflags(ef);
+}
+
 static int
 sysctl_machdep_i586_freq SYSCTL_HANDLER_ARGS
 {
 	int error;
 	u_int freq;
 
-	if (i586_ctr_rate == 0)
+	if (cpu_class != CPUCLASS_586 && cpu_class != CPUCLASS_686)
 		return (EOPNOTSUPP);
 	freq = i586_ctr_freq;
 	error = sysctl_handle_opaque(oidp, &freq, sizeof freq, req);
-	if (error == 0 && freq != i586_ctr_freq) {
-		i586_ctr_freq = freq;
-		i586_ctr_rate = ((unsigned long long)freq <<
-				 I586_CTR_RATE_SHIFT) / 1000000;
-	}
+	if (error == 0 && req->newptr != NULL)
+		set_i586_ctr_freq(freq, timer_freq);
 	return (error);
 }
 
diff --git a/sys/i386/include/clock.h b/sys/i386/include/clock.h
index 830ae1367a08e..043936310dd5b 100644
--- a/sys/i386/include/clock.h
+++ b/sys/i386/include/clock.h
@@ -3,7 +3,7 @@
  * Garrett Wollman, September 1994.
  * This file is in the public domain.
  *
- *	$Id: clock.h,v 1.13 1996/05/01 08:38:50 bde Exp $
+ *	$Id: clock.h,v 1.14 1996/06/14 11:00:56 asami Exp $
  */
 
 #ifndef _MACHINE_CLOCK_H_
@@ -38,6 +38,8 @@
 #define CPU_THISTICKLEN(dflt) dflt
 #endif
 
+#define	I586_CTR_COMULTIPLIER_SHIFT	20
+#define	I586_CTR_MULTIPLIER_SHIFT	32
 #define		I586_CTR_RATE_SHIFT	8
 
 #if defined(KERNEL) && !defined(LOCORE)
@@ -55,7 +57,9 @@ extern int	statclock_disable;
 extern int	wall_cmos_clock;
 
 #if defined(I586_CPU) || defined(I686_CPU)
-extern unsigned	i586_ctr_freq;
+extern u_int	i586_ctr_comultiplier;
+extern u_int	i586_ctr_freq;
+extern u_int	i586_ctr_multiplier;
 extern unsigned	i586_ctr_rate;	/* fixed point */
 extern long long i586_last_tick;
 extern long long i586_ctr_bias;
diff --git a/sys/i386/isa/clock.c b/sys/i386/isa/clock.c
index 58678a6ea3778..7257b2fb8226a 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 1.64 1996/07/20 18:47:23 joerg Exp $
+ *	$Id: clock.c,v 1.65 1996/07/21 08:20:51 joerg Exp $
  */
 
 /*
@@ -102,7 +102,9 @@ int	wall_cmos_clock;	/* wall	CMOS clock assumed if != 0 */
 
 u_int	idelayed;
 #if defined(I586_CPU) || defined(I686_CPU)
-unsigned	i586_ctr_freq;
+u_int	i586_ctr_comultiplier;
+u_int	i586_ctr_freq;
+u_int	i586_ctr_multiplier;
 unsigned	i586_ctr_rate;
 long long	i586_ctr_bias;
 long long	i586_last_tick;
@@ -144,6 +146,10 @@ static	u_char	timer0_state;
 static	u_char	timer2_state;
 static 	void	(*timer_func) __P((struct clockframe *frame)) = hardclock;
 
+#if defined(I586_CPU) || defined(I686_CPU)
+static	void	set_i586_ctr_freq(u_int i586_freq, u_int i8254_freq);
+#endif
+
 static void
 clkintr(struct clockframe frame)
 {
@@ -553,11 +559,7 @@ calibrate_clocks(void)
 	 * similar to those for the i8254 clock.
 	 */
 	if (cpu_class == CPUCLASS_586 || cpu_class == CPUCLASS_686) {
-		unsigned long long i586_count;
-
-		i586_count = rdtsc();
-		i586_ctr_freq = i586_count;
-		i586_ctr_rate = (i586_count << I586_CTR_RATE_SHIFT) / 1000000;
+		set_i586_ctr_freq((u_int)rdtsc(), tot_count);
 		printf("i586 clock: %u Hz, ", i586_ctr_freq);
 	}
 #endif
@@ -651,12 +653,9 @@ startrtclock()
 		 * clock failed.  Do a less accurate calibration relative
 		 * to the i8254 clock.
 		 */
-		unsigned long long i586_count;
-
 		wrmsr(0x10, 0LL);	/* XXX */
 		DELAY(1000000);
-		i586_count = rdtsc();
-		i586_ctr_rate = (i586_count << I586_CTR_RATE_SHIFT) / 1000000;
+		set_i586_ctr_freq((u_int)rdtsc(), timer_freq);
 #ifdef CLK_USE_I586_CALIBRATION
 		printf("i586 clock: %u Hz\n", i586_ctr_freq);
 #endif
@@ -861,10 +860,13 @@ sysctl_machdep_i8254_freq SYSCTL_HANDLER_ARGS
 	 */
 	freq = timer_freq;
 	error = sysctl_handle_opaque(oidp, &freq, sizeof freq, req);
-	if (error == 0 && freq != timer_freq) {
+	if (error == 0 && req->newptr != NULL) {
 		if (timer0_state != 0)
 			return (EBUSY);	/* too much trouble to handle */
 		set_timer_freq(freq, hz);
+#if defined(I586_CPU) || defined(I686_CPU)
+		set_i586_ctr_freq(i586_ctr_freq, timer_freq);
+#endif
 	}
 	return (error);
 }
@@ -873,21 +875,42 @@ SYSCTL_PROC(_machdep, OID_AUTO, i8254_freq, CTLTYPE_INT | CTLFLAG_RW,
 	    0, sizeof(u_int), sysctl_machdep_i8254_freq, "I", "");
 
 #if defined(I586_CPU) || defined(I686_CPU)
+static void
+set_i586_ctr_freq(u_int i586_freq, u_int i8254_freq)
+{
+	u_int comultiplier, multiplier, rate;
+	u_long ef;
+
+	if (i586_freq == 0) {
+		i586_ctr_freq = i586_freq;
+		i586_ctr_rate = 0;
+		return;
+	}
+	comultiplier = ((unsigned long long)i586_freq
+			<< I586_CTR_COMULTIPLIER_SHIFT) / i8254_freq;
+	multiplier = (1000000LL << I586_CTR_MULTIPLIER_SHIFT) / i586_freq;
+	rate = ((unsigned long long)i586_freq << I586_CTR_RATE_SHIFT) / 1000000;
+	ef = read_eflags();
+	disable_intr();
+	i586_ctr_freq = i586_freq;
+	i586_ctr_comultiplier = comultiplier;
+	i586_ctr_multiplier = multiplier;
+	i586_ctr_rate = rate;
+	write_eflags(ef);
+}
+
 static int
 sysctl_machdep_i586_freq SYSCTL_HANDLER_ARGS
 {
 	int error;
 	u_int freq;
 
-	if (i586_ctr_rate == 0)
+	if (cpu_class != CPUCLASS_586 && cpu_class != CPUCLASS_686)
 		return (EOPNOTSUPP);
 	freq = i586_ctr_freq;
 	error = sysctl_handle_opaque(oidp, &freq, sizeof freq, req);
-	if (error == 0 && freq != i586_ctr_freq) {
-		i586_ctr_freq = freq;
-		i586_ctr_rate = ((unsigned long long)freq <<
-				 I586_CTR_RATE_SHIFT) / 1000000;
-	}
+	if (error == 0 && req->newptr != NULL)
+		set_i586_ctr_freq(freq, timer_freq);
 	return (error);
 }
 
diff --git a/sys/isa/atrtc.c b/sys/isa/atrtc.c
index 58678a6ea3778..7257b2fb8226a 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 1.64 1996/07/20 18:47:23 joerg Exp $
+ *	$Id: clock.c,v 1.65 1996/07/21 08:20:51 joerg Exp $
  */
 
 /*
@@ -102,7 +102,9 @@ int	wall_cmos_clock;	/* wall	CMOS clock assumed if != 0 */
 
 u_int	idelayed;
 #if defined(I586_CPU) || defined(I686_CPU)
-unsigned	i586_ctr_freq;
+u_int	i586_ctr_comultiplier;
+u_int	i586_ctr_freq;
+u_int	i586_ctr_multiplier;
 unsigned	i586_ctr_rate;
 long long	i586_ctr_bias;
 long long	i586_last_tick;
@@ -144,6 +146,10 @@ static	u_char	timer0_state;
 static	u_char	timer2_state;
 static 	void	(*timer_func) __P((struct clockframe *frame)) = hardclock;
 
+#if defined(I586_CPU) || defined(I686_CPU)
+static	void	set_i586_ctr_freq(u_int i586_freq, u_int i8254_freq);
+#endif
+
 static void
 clkintr(struct clockframe frame)
 {
@@ -553,11 +559,7 @@ calibrate_clocks(void)
 	 * similar to those for the i8254 clock.
 	 */
 	if (cpu_class == CPUCLASS_586 || cpu_class == CPUCLASS_686) {
-		unsigned long long i586_count;
-
-		i586_count = rdtsc();
-		i586_ctr_freq = i586_count;
-		i586_ctr_rate = (i586_count << I586_CTR_RATE_SHIFT) / 1000000;
+		set_i586_ctr_freq((u_int)rdtsc(), tot_count);
 		printf("i586 clock: %u Hz, ", i586_ctr_freq);
 	}
 #endif
@@ -651,12 +653,9 @@ startrtclock()
 		 * clock failed.  Do a less accurate calibration relative
 		 * to the i8254 clock.
 		 */
-		unsigned long long i586_count;
-
 		wrmsr(0x10, 0LL);	/* XXX */
 		DELAY(1000000);
-		i586_count = rdtsc();
-		i586_ctr_rate = (i586_count << I586_CTR_RATE_SHIFT) / 1000000;
+		set_i586_ctr_freq((u_int)rdtsc(), timer_freq);
 #ifdef CLK_USE_I586_CALIBRATION
 		printf("i586 clock: %u Hz\n", i586_ctr_freq);
 #endif
@@ -861,10 +860,13 @@ sysctl_machdep_i8254_freq SYSCTL_HANDLER_ARGS
 	 */
 	freq = timer_freq;
 	error = sysctl_handle_opaque(oidp, &freq, sizeof freq, req);
-	if (error == 0 && freq != timer_freq) {
+	if (error == 0 && req->newptr != NULL) {
 		if (timer0_state != 0)
 			return (EBUSY);	/* too much trouble to handle */
 		set_timer_freq(freq, hz);
+#if defined(I586_CPU) || defined(I686_CPU)
+		set_i586_ctr_freq(i586_ctr_freq, timer_freq);
+#endif
 	}
 	return (error);
 }
@@ -873,21 +875,42 @@ SYSCTL_PROC(_machdep, OID_AUTO, i8254_freq, CTLTYPE_INT | CTLFLAG_RW,
 	    0, sizeof(u_int), sysctl_machdep_i8254_freq, "I", "");
 
 #if defined(I586_CPU) || defined(I686_CPU)
+static void
+set_i586_ctr_freq(u_int i586_freq, u_int i8254_freq)
+{
+	u_int comultiplier, multiplier, rate;
+	u_long ef;
+
+	if (i586_freq == 0) {
+		i586_ctr_freq = i586_freq;
+		i586_ctr_rate = 0;
+		return;
+	}
+	comultiplier = ((unsigned long long)i586_freq
+			<< I586_CTR_COMULTIPLIER_SHIFT) / i8254_freq;
+	multiplier = (1000000LL << I586_CTR_MULTIPLIER_SHIFT) / i586_freq;
+	rate = ((unsigned long long)i586_freq << I586_CTR_RATE_SHIFT) / 1000000;
+	ef = read_eflags();
+	disable_intr();
+	i586_ctr_freq = i586_freq;
+	i586_ctr_comultiplier = comultiplier;
+	i586_ctr_multiplier = multiplier;
+	i586_ctr_rate = rate;
+	write_eflags(ef);
+}
+
 static int
 sysctl_machdep_i586_freq SYSCTL_HANDLER_ARGS
 {
 	int error;
 	u_int freq;
 
-	if (i586_ctr_rate == 0)
+	if (cpu_class != CPUCLASS_586 && cpu_class != CPUCLASS_686)
 		return (EOPNOTSUPP);
 	freq = i586_ctr_freq;
 	error = sysctl_handle_opaque(oidp, &freq, sizeof freq, req);
-	if (error == 0 && freq != i586_ctr_freq) {
-		i586_ctr_freq = freq;
-		i586_ctr_rate = ((unsigned long long)freq <<
-				 I586_CTR_RATE_SHIFT) / 1000000;
-	}
+	if (error == 0 && req->newptr != NULL)
+		set_i586_ctr_freq(freq, timer_freq);
 	return (error);
 }