diff --git a/sys/amd64/amd64/apic_vector.S b/sys/amd64/amd64/apic_vector.S
index 88340e6626b6..66d53a6a2ce0 100644
--- a/sys/amd64/amd64/apic_vector.S
+++ b/sys/amd64/amd64/apic_vector.S
@@ -1,6 +1,6 @@
 /*
  *	from: vector.s, 386BSD 0.1 unknown origin
- *	$Id: apic_vector.s,v 1.36 1999/04/14 14:26:35 bde Exp $
+ *	$Id: apic_vector.s,v 1.37 1999/04/28 01:04:12 luoqi Exp $
  */
 
 
@@ -324,7 +324,7 @@ log_intr_event:
 		
 #ifdef CPL_AND_CML
 
-#define	INTR(irq_num, vec_name)						\
+#define	INTR(irq_num, vec_name, maybe_extra_ipending)			\
 	.text ;								\
 	SUPERALIGN_TEXT ;						\
 /* _XintrNN: entry point used by IDT/HWIs & splz_unpend via _vec[]. */	\
@@ -335,6 +335,8 @@ IDTVEC(vec_name) ;							\
 	movl	%ax, %es ;						\
 	movl	$KPSEL, %eax ;						\
 	movl	%ax, %fs ;						\
+;									\
+	maybe_extra_ipending ;						\
 ;									\
 	APIC_ITRACE(apic_itrace_enter, irq_num, APIC_ITRACE_ENTER) ;	\
 	lock ;					/* MP-safe */		\
@@ -436,7 +438,7 @@ __CONCAT(Xresume,irq_num): ;						\
 #else /* CPL_AND_CML */
 
 
-#define	INTR(irq_num, vec_name)						\
+#define	INTR(irq_num, vec_name, maybe_extra_ipending)			\
 	.text ;								\
 	SUPERALIGN_TEXT ;						\
 /* _XintrNN: entry point used by IDT/HWIs & splz_unpend via _vec[]. */	\
@@ -447,6 +449,8 @@ IDTVEC(vec_name) ;							\
 	movl	%ax, %es ;						\
 	movl	$KPSEL, %eax ;						\
 	movl	%ax, %fs ;						\
+;									\
+	maybe_extra_ipending ;						\
 ;									\
 	APIC_ITRACE(apic_itrace_enter, irq_num, APIC_ITRACE_ENTER) ;	\
 	lock ;					/* MP-safe */		\
@@ -916,30 +920,31 @@ MCOUNT_LABEL(bintr)
 	FAST_INTR(21,fastintr21)
 	FAST_INTR(22,fastintr22)
 	FAST_INTR(23,fastintr23)
-	INTR(0,intr0)
-	INTR(1,intr1)
-	INTR(2,intr2)
-	INTR(3,intr3)
-	INTR(4,intr4)
-	INTR(5,intr5)
-	INTR(6,intr6)
-	INTR(7,intr7)
-	INTR(8,intr8)
-	INTR(9,intr9)
-	INTR(10,intr10)
-	INTR(11,intr11)
-	INTR(12,intr12)
-	INTR(13,intr13)
-	INTR(14,intr14)
-	INTR(15,intr15)
-	INTR(16,intr16)
-	INTR(17,intr17)
-	INTR(18,intr18)
-	INTR(19,intr19)
-	INTR(20,intr20)
-	INTR(21,intr21)
-	INTR(22,intr22)
-	INTR(23,intr23)
+#define	CLKINTR_PENDING	movl $1,CNAME(clkintr_pending)
+	INTR(0,intr0, CLKINTR_PENDING)
+	INTR(1,intr1,)
+	INTR(2,intr2,)
+	INTR(3,intr3,)
+	INTR(4,intr4,)
+	INTR(5,intr5,)
+	INTR(6,intr6,)
+	INTR(7,intr7,)
+	INTR(8,intr8,)
+	INTR(9,intr9,)
+	INTR(10,intr10,)
+	INTR(11,intr11,)
+	INTR(12,intr12,)
+	INTR(13,intr13,)
+	INTR(14,intr14,)
+	INTR(15,intr15,)
+	INTR(16,intr16,)
+	INTR(17,intr17,)
+	INTR(18,intr18,)
+	INTR(19,intr19,)
+	INTR(20,intr20,)
+	INTR(21,intr21,)
+	INTR(22,intr22,)
+	INTR(23,intr23,)
 MCOUNT_LABEL(eintr)
 
 	.data
diff --git a/sys/amd64/amd64/tsc.c b/sys/amd64/amd64/tsc.c
index d9ee00edd9a5..75511f411e12 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 1.132 1999/04/25 09:00:00 phk Exp $
+ *	$Id: clock.c,v 1.133 1999/05/09 23:32:29 peter Exp $
  */
 
 /*
@@ -69,6 +69,7 @@
 #include <machine/ipl.h>
 #include <machine/limits.h>
 #include <machine/md_var.h>
+#include <machine/psl.h>
 #if NAPM > 0
 #include <machine/apm_bios.h>
 #include <i386/apm/apm_setup.h>
@@ -127,6 +128,7 @@ static void setup_8254_mixed_mode __P((void));
 #define	TIMER0_MAX_FREQ		20000
 
 int	adjkerntz;		/* local offset from GMT in seconds */
+int	clkintr_pending;
 int	disable_rtc_set;	/* disable resettodr() if != 0 */
 volatile u_int	idelayed;
 int	statclock_disable;
@@ -199,24 +201,15 @@ static void
 clkintr(struct clockframe frame)
 {
 	if (timecounter->tc_get_timecount == i8254_get_timecount) {
-		/*
-		 * Maintain i8254_offset and related variables.  Optimize
-		 * the usual case where i8254 counter rollover has not been
-		 * detected in i8254_get_timecount() by pretending that we
-		 * read the counter when it rolled over.  Otherwise, call
-		 * i8254_get_timecount() to do most of the work.  The
-		 * hardware counter must be read to ensure monotonicity
-		 * despite multiple rollovers and misbehaving hardware.
-		 */
-		(disable_intr)();	/* XXX avoid clock locking */
-		if (i8254_ticked) {
-			i8254_get_timecount(NULL);
+		disable_intr();
+		if (i8254_ticked)
 			i8254_ticked = 0;
-		} else {
+		else {
 			i8254_offset += timer0_max_count;
 			i8254_lastcount = 0;
 		}
-		(enable_intr)();	/* XXX avoid clock locking */
+		clkintr_pending = 0;
+		enable_intr();
 	}
 	timer_func(&frame);
 	switch (timer0_state) {
@@ -1159,13 +1152,21 @@ i8254_get_timecount(struct timecounter *tc)
 
 	low = inb(TIMER_CNTR0);
 	high = inb(TIMER_CNTR0);
-
-	count = hardclock_max_count - ((high << 8) | low);
-	if (count < i8254_lastcount) {
+	count = timer0_max_count - ((high << 8) | low);
+	if (count < i8254_lastcount ||
+	    (!i8254_ticked && (clkintr_pending ||
+	    ((count < 20 || (!(ef & PSL_I) && count < timer0_max_count / 2u)) &&
+#ifdef APIC_IO
+#define	lapic_irr1	((volatile u_int *)&lapic)[0x210 / 4]	/* XXX XXX */
+	    /* XXX this assumes that apic_8254_intr is < 24. */
+	    (lapic_irr1 & (1 << apic_8254_intr))))
+#else
+	    (inb(IO_ICU1) & 1)))
+#endif
+	    )) {
 		i8254_ticked = 1;
-		i8254_offset += hardclock_max_count;
+		i8254_offset += timer0_max_count;
 	}
-
 	i8254_lastcount = count;
 	count += i8254_offset;
 	CLOCK_UNLOCK();
diff --git a/sys/amd64/isa/atpic_vector.S b/sys/amd64/isa/atpic_vector.S
index 446030303231..453f9d553b84 100644
--- a/sys/amd64/isa/atpic_vector.S
+++ b/sys/amd64/isa/atpic_vector.S
@@ -1,6 +1,6 @@
 /*
  *	from: vector.s, 386BSD 0.1 unknown origin
- *	$Id: icu_vector.s,v 1.10 1999/04/14 14:26:36 bde Exp $
+ *	$Id: icu_vector.s,v 1.11 1999/04/28 01:04:13 luoqi Exp $
  */
 
 /*
@@ -106,7 +106,7 @@ IDTVEC(vec_name) ; \
 	MEXITCOUNT ; \
 	jmp	_doreti
 
-#define	INTR(irq_num, vec_name, icu, enable_icus, reg) \
+#define	INTR(irq_num, vec_name, icu, enable_icus, reg, maybe_extra_ipending) \
 	.text ; \
 	SUPERALIGN_TEXT ; \
 IDTVEC(vec_name) ; \
@@ -120,6 +120,7 @@ IDTVEC(vec_name) ; \
 	movl	%ax,%ds ;	/* ... early for obsolete reasons */ \
 	movl	%ax,%es ; \
 	movl	%ax,%fs ; \
+	maybe_extra_ipending ; \
 	movb	_imen + IRQ_BYTE(irq_num),%al ; \
 	orb	$IRQ_BIT(irq_num),%al ; \
 	movb	%al,_imen + IRQ_BYTE(irq_num) ; \
@@ -180,22 +181,23 @@ MCOUNT_LABEL(bintr)
 	FAST_INTR(13,fastintr13, ENABLE_ICU1_AND_2)
 	FAST_INTR(14,fastintr14, ENABLE_ICU1_AND_2)
 	FAST_INTR(15,fastintr15, ENABLE_ICU1_AND_2)
-	INTR(0,intr0, IO_ICU1, ENABLE_ICU1, al)
-	INTR(1,intr1, IO_ICU1, ENABLE_ICU1, al)
-	INTR(2,intr2, IO_ICU1, ENABLE_ICU1, al)
-	INTR(3,intr3, IO_ICU1, ENABLE_ICU1, al)
-	INTR(4,intr4, IO_ICU1, ENABLE_ICU1, al)
-	INTR(5,intr5, IO_ICU1, ENABLE_ICU1, al)
-	INTR(6,intr6, IO_ICU1, ENABLE_ICU1, al)
-	INTR(7,intr7, IO_ICU1, ENABLE_ICU1, al)
-	INTR(8,intr8, IO_ICU2, ENABLE_ICU1_AND_2, ah)
-	INTR(9,intr9, IO_ICU2, ENABLE_ICU1_AND_2, ah)
-	INTR(10,intr10, IO_ICU2, ENABLE_ICU1_AND_2, ah)
-	INTR(11,intr11, IO_ICU2, ENABLE_ICU1_AND_2, ah)
-	INTR(12,intr12, IO_ICU2, ENABLE_ICU1_AND_2, ah)
-	INTR(13,intr13, IO_ICU2, ENABLE_ICU1_AND_2, ah)
-	INTR(14,intr14, IO_ICU2, ENABLE_ICU1_AND_2, ah)
-	INTR(15,intr15, IO_ICU2, ENABLE_ICU1_AND_2, ah)
+#define	CLKINTR_PENDING	movl $1,CNAME(clkintr_pending)
+	INTR(0,intr0, IO_ICU1, ENABLE_ICU1, al, CLKINTR_PENDING)
+	INTR(1,intr1, IO_ICU1, ENABLE_ICU1, al,)
+	INTR(2,intr2, IO_ICU1, ENABLE_ICU1, al,)
+	INTR(3,intr3, IO_ICU1, ENABLE_ICU1, al,)
+	INTR(4,intr4, IO_ICU1, ENABLE_ICU1, al,)
+	INTR(5,intr5, IO_ICU1, ENABLE_ICU1, al,)
+	INTR(6,intr6, IO_ICU1, ENABLE_ICU1, al,)
+	INTR(7,intr7, IO_ICU1, ENABLE_ICU1, al,)
+	INTR(8,intr8, IO_ICU2, ENABLE_ICU1_AND_2, ah,)
+	INTR(9,intr9, IO_ICU2, ENABLE_ICU1_AND_2, ah,)
+	INTR(10,intr10, IO_ICU2, ENABLE_ICU1_AND_2, ah,)
+	INTR(11,intr11, IO_ICU2, ENABLE_ICU1_AND_2, ah,)
+	INTR(12,intr12, IO_ICU2, ENABLE_ICU1_AND_2, ah,)
+	INTR(13,intr13, IO_ICU2, ENABLE_ICU1_AND_2, ah,)
+	INTR(14,intr14, IO_ICU2, ENABLE_ICU1_AND_2, ah,)
+	INTR(15,intr15, IO_ICU2, ENABLE_ICU1_AND_2, ah,)
 MCOUNT_LABEL(eintr)
 
 	.data
diff --git a/sys/amd64/isa/clock.c b/sys/amd64/isa/clock.c
index d9ee00edd9a5..75511f411e12 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 1.132 1999/04/25 09:00:00 phk Exp $
+ *	$Id: clock.c,v 1.133 1999/05/09 23:32:29 peter Exp $
  */
 
 /*
@@ -69,6 +69,7 @@
 #include <machine/ipl.h>
 #include <machine/limits.h>
 #include <machine/md_var.h>
+#include <machine/psl.h>
 #if NAPM > 0
 #include <machine/apm_bios.h>
 #include <i386/apm/apm_setup.h>
@@ -127,6 +128,7 @@ static void setup_8254_mixed_mode __P((void));
 #define	TIMER0_MAX_FREQ		20000
 
 int	adjkerntz;		/* local offset from GMT in seconds */
+int	clkintr_pending;
 int	disable_rtc_set;	/* disable resettodr() if != 0 */
 volatile u_int	idelayed;
 int	statclock_disable;
@@ -199,24 +201,15 @@ static void
 clkintr(struct clockframe frame)
 {
 	if (timecounter->tc_get_timecount == i8254_get_timecount) {
-		/*
-		 * Maintain i8254_offset and related variables.  Optimize
-		 * the usual case where i8254 counter rollover has not been
-		 * detected in i8254_get_timecount() by pretending that we
-		 * read the counter when it rolled over.  Otherwise, call
-		 * i8254_get_timecount() to do most of the work.  The
-		 * hardware counter must be read to ensure monotonicity
-		 * despite multiple rollovers and misbehaving hardware.
-		 */
-		(disable_intr)();	/* XXX avoid clock locking */
-		if (i8254_ticked) {
-			i8254_get_timecount(NULL);
+		disable_intr();
+		if (i8254_ticked)
 			i8254_ticked = 0;
-		} else {
+		else {
 			i8254_offset += timer0_max_count;
 			i8254_lastcount = 0;
 		}
-		(enable_intr)();	/* XXX avoid clock locking */
+		clkintr_pending = 0;
+		enable_intr();
 	}
 	timer_func(&frame);
 	switch (timer0_state) {
@@ -1159,13 +1152,21 @@ i8254_get_timecount(struct timecounter *tc)
 
 	low = inb(TIMER_CNTR0);
 	high = inb(TIMER_CNTR0);
-
-	count = hardclock_max_count - ((high << 8) | low);
-	if (count < i8254_lastcount) {
+	count = timer0_max_count - ((high << 8) | low);
+	if (count < i8254_lastcount ||
+	    (!i8254_ticked && (clkintr_pending ||
+	    ((count < 20 || (!(ef & PSL_I) && count < timer0_max_count / 2u)) &&
+#ifdef APIC_IO
+#define	lapic_irr1	((volatile u_int *)&lapic)[0x210 / 4]	/* XXX XXX */
+	    /* XXX this assumes that apic_8254_intr is < 24. */
+	    (lapic_irr1 & (1 << apic_8254_intr))))
+#else
+	    (inb(IO_ICU1) & 1)))
+#endif
+	    )) {
 		i8254_ticked = 1;
-		i8254_offset += hardclock_max_count;
+		i8254_offset += timer0_max_count;
 	}
-
 	i8254_lastcount = count;
 	count += i8254_offset;
 	CLOCK_UNLOCK();
diff --git a/sys/amd64/isa/icu_vector.S b/sys/amd64/isa/icu_vector.S
index 446030303231..453f9d553b84 100644
--- a/sys/amd64/isa/icu_vector.S
+++ b/sys/amd64/isa/icu_vector.S
@@ -1,6 +1,6 @@
 /*
  *	from: vector.s, 386BSD 0.1 unknown origin
- *	$Id: icu_vector.s,v 1.10 1999/04/14 14:26:36 bde Exp $
+ *	$Id: icu_vector.s,v 1.11 1999/04/28 01:04:13 luoqi Exp $
  */
 
 /*
@@ -106,7 +106,7 @@ IDTVEC(vec_name) ; \
 	MEXITCOUNT ; \
 	jmp	_doreti
 
-#define	INTR(irq_num, vec_name, icu, enable_icus, reg) \
+#define	INTR(irq_num, vec_name, icu, enable_icus, reg, maybe_extra_ipending) \
 	.text ; \
 	SUPERALIGN_TEXT ; \
 IDTVEC(vec_name) ; \
@@ -120,6 +120,7 @@ IDTVEC(vec_name) ; \
 	movl	%ax,%ds ;	/* ... early for obsolete reasons */ \
 	movl	%ax,%es ; \
 	movl	%ax,%fs ; \
+	maybe_extra_ipending ; \
 	movb	_imen + IRQ_BYTE(irq_num),%al ; \
 	orb	$IRQ_BIT(irq_num),%al ; \
 	movb	%al,_imen + IRQ_BYTE(irq_num) ; \
@@ -180,22 +181,23 @@ MCOUNT_LABEL(bintr)
 	FAST_INTR(13,fastintr13, ENABLE_ICU1_AND_2)
 	FAST_INTR(14,fastintr14, ENABLE_ICU1_AND_2)
 	FAST_INTR(15,fastintr15, ENABLE_ICU1_AND_2)
-	INTR(0,intr0, IO_ICU1, ENABLE_ICU1, al)
-	INTR(1,intr1, IO_ICU1, ENABLE_ICU1, al)
-	INTR(2,intr2, IO_ICU1, ENABLE_ICU1, al)
-	INTR(3,intr3, IO_ICU1, ENABLE_ICU1, al)
-	INTR(4,intr4, IO_ICU1, ENABLE_ICU1, al)
-	INTR(5,intr5, IO_ICU1, ENABLE_ICU1, al)
-	INTR(6,intr6, IO_ICU1, ENABLE_ICU1, al)
-	INTR(7,intr7, IO_ICU1, ENABLE_ICU1, al)
-	INTR(8,intr8, IO_ICU2, ENABLE_ICU1_AND_2, ah)
-	INTR(9,intr9, IO_ICU2, ENABLE_ICU1_AND_2, ah)
-	INTR(10,intr10, IO_ICU2, ENABLE_ICU1_AND_2, ah)
-	INTR(11,intr11, IO_ICU2, ENABLE_ICU1_AND_2, ah)
-	INTR(12,intr12, IO_ICU2, ENABLE_ICU1_AND_2, ah)
-	INTR(13,intr13, IO_ICU2, ENABLE_ICU1_AND_2, ah)
-	INTR(14,intr14, IO_ICU2, ENABLE_ICU1_AND_2, ah)
-	INTR(15,intr15, IO_ICU2, ENABLE_ICU1_AND_2, ah)
+#define	CLKINTR_PENDING	movl $1,CNAME(clkintr_pending)
+	INTR(0,intr0, IO_ICU1, ENABLE_ICU1, al, CLKINTR_PENDING)
+	INTR(1,intr1, IO_ICU1, ENABLE_ICU1, al,)
+	INTR(2,intr2, IO_ICU1, ENABLE_ICU1, al,)
+	INTR(3,intr3, IO_ICU1, ENABLE_ICU1, al,)
+	INTR(4,intr4, IO_ICU1, ENABLE_ICU1, al,)
+	INTR(5,intr5, IO_ICU1, ENABLE_ICU1, al,)
+	INTR(6,intr6, IO_ICU1, ENABLE_ICU1, al,)
+	INTR(7,intr7, IO_ICU1, ENABLE_ICU1, al,)
+	INTR(8,intr8, IO_ICU2, ENABLE_ICU1_AND_2, ah,)
+	INTR(9,intr9, IO_ICU2, ENABLE_ICU1_AND_2, ah,)
+	INTR(10,intr10, IO_ICU2, ENABLE_ICU1_AND_2, ah,)
+	INTR(11,intr11, IO_ICU2, ENABLE_ICU1_AND_2, ah,)
+	INTR(12,intr12, IO_ICU2, ENABLE_ICU1_AND_2, ah,)
+	INTR(13,intr13, IO_ICU2, ENABLE_ICU1_AND_2, ah,)
+	INTR(14,intr14, IO_ICU2, ENABLE_ICU1_AND_2, ah,)
+	INTR(15,intr15, IO_ICU2, ENABLE_ICU1_AND_2, ah,)
 MCOUNT_LABEL(eintr)
 
 	.data
diff --git a/sys/amd64/isa/icu_vector.s b/sys/amd64/isa/icu_vector.s
index 446030303231..453f9d553b84 100644
--- a/sys/amd64/isa/icu_vector.s
+++ b/sys/amd64/isa/icu_vector.s
@@ -1,6 +1,6 @@
 /*
  *	from: vector.s, 386BSD 0.1 unknown origin
- *	$Id: icu_vector.s,v 1.10 1999/04/14 14:26:36 bde Exp $
+ *	$Id: icu_vector.s,v 1.11 1999/04/28 01:04:13 luoqi Exp $
  */
 
 /*
@@ -106,7 +106,7 @@ IDTVEC(vec_name) ; \
 	MEXITCOUNT ; \
 	jmp	_doreti
 
-#define	INTR(irq_num, vec_name, icu, enable_icus, reg) \
+#define	INTR(irq_num, vec_name, icu, enable_icus, reg, maybe_extra_ipending) \
 	.text ; \
 	SUPERALIGN_TEXT ; \
 IDTVEC(vec_name) ; \
@@ -120,6 +120,7 @@ IDTVEC(vec_name) ; \
 	movl	%ax,%ds ;	/* ... early for obsolete reasons */ \
 	movl	%ax,%es ; \
 	movl	%ax,%fs ; \
+	maybe_extra_ipending ; \
 	movb	_imen + IRQ_BYTE(irq_num),%al ; \
 	orb	$IRQ_BIT(irq_num),%al ; \
 	movb	%al,_imen + IRQ_BYTE(irq_num) ; \
@@ -180,22 +181,23 @@ MCOUNT_LABEL(bintr)
 	FAST_INTR(13,fastintr13, ENABLE_ICU1_AND_2)
 	FAST_INTR(14,fastintr14, ENABLE_ICU1_AND_2)
 	FAST_INTR(15,fastintr15, ENABLE_ICU1_AND_2)
-	INTR(0,intr0, IO_ICU1, ENABLE_ICU1, al)
-	INTR(1,intr1, IO_ICU1, ENABLE_ICU1, al)
-	INTR(2,intr2, IO_ICU1, ENABLE_ICU1, al)
-	INTR(3,intr3, IO_ICU1, ENABLE_ICU1, al)
-	INTR(4,intr4, IO_ICU1, ENABLE_ICU1, al)
-	INTR(5,intr5, IO_ICU1, ENABLE_ICU1, al)
-	INTR(6,intr6, IO_ICU1, ENABLE_ICU1, al)
-	INTR(7,intr7, IO_ICU1, ENABLE_ICU1, al)
-	INTR(8,intr8, IO_ICU2, ENABLE_ICU1_AND_2, ah)
-	INTR(9,intr9, IO_ICU2, ENABLE_ICU1_AND_2, ah)
-	INTR(10,intr10, IO_ICU2, ENABLE_ICU1_AND_2, ah)
-	INTR(11,intr11, IO_ICU2, ENABLE_ICU1_AND_2, ah)
-	INTR(12,intr12, IO_ICU2, ENABLE_ICU1_AND_2, ah)
-	INTR(13,intr13, IO_ICU2, ENABLE_ICU1_AND_2, ah)
-	INTR(14,intr14, IO_ICU2, ENABLE_ICU1_AND_2, ah)
-	INTR(15,intr15, IO_ICU2, ENABLE_ICU1_AND_2, ah)
+#define	CLKINTR_PENDING	movl $1,CNAME(clkintr_pending)
+	INTR(0,intr0, IO_ICU1, ENABLE_ICU1, al, CLKINTR_PENDING)
+	INTR(1,intr1, IO_ICU1, ENABLE_ICU1, al,)
+	INTR(2,intr2, IO_ICU1, ENABLE_ICU1, al,)
+	INTR(3,intr3, IO_ICU1, ENABLE_ICU1, al,)
+	INTR(4,intr4, IO_ICU1, ENABLE_ICU1, al,)
+	INTR(5,intr5, IO_ICU1, ENABLE_ICU1, al,)
+	INTR(6,intr6, IO_ICU1, ENABLE_ICU1, al,)
+	INTR(7,intr7, IO_ICU1, ENABLE_ICU1, al,)
+	INTR(8,intr8, IO_ICU2, ENABLE_ICU1_AND_2, ah,)
+	INTR(9,intr9, IO_ICU2, ENABLE_ICU1_AND_2, ah,)
+	INTR(10,intr10, IO_ICU2, ENABLE_ICU1_AND_2, ah,)
+	INTR(11,intr11, IO_ICU2, ENABLE_ICU1_AND_2, ah,)
+	INTR(12,intr12, IO_ICU2, ENABLE_ICU1_AND_2, ah,)
+	INTR(13,intr13, IO_ICU2, ENABLE_ICU1_AND_2, ah,)
+	INTR(14,intr14, IO_ICU2, ENABLE_ICU1_AND_2, ah,)
+	INTR(15,intr15, IO_ICU2, ENABLE_ICU1_AND_2, ah,)
 MCOUNT_LABEL(eintr)
 
 	.data
diff --git a/sys/i386/i386/apic_vector.s b/sys/i386/i386/apic_vector.s
index 88340e6626b6..66d53a6a2ce0 100644
--- a/sys/i386/i386/apic_vector.s
+++ b/sys/i386/i386/apic_vector.s
@@ -1,6 +1,6 @@
 /*
  *	from: vector.s, 386BSD 0.1 unknown origin
- *	$Id: apic_vector.s,v 1.36 1999/04/14 14:26:35 bde Exp $
+ *	$Id: apic_vector.s,v 1.37 1999/04/28 01:04:12 luoqi Exp $
  */
 
 
@@ -324,7 +324,7 @@ log_intr_event:
 		
 #ifdef CPL_AND_CML
 
-#define	INTR(irq_num, vec_name)						\
+#define	INTR(irq_num, vec_name, maybe_extra_ipending)			\
 	.text ;								\
 	SUPERALIGN_TEXT ;						\
 /* _XintrNN: entry point used by IDT/HWIs & splz_unpend via _vec[]. */	\
@@ -335,6 +335,8 @@ IDTVEC(vec_name) ;							\
 	movl	%ax, %es ;						\
 	movl	$KPSEL, %eax ;						\
 	movl	%ax, %fs ;						\
+;									\
+	maybe_extra_ipending ;						\
 ;									\
 	APIC_ITRACE(apic_itrace_enter, irq_num, APIC_ITRACE_ENTER) ;	\
 	lock ;					/* MP-safe */		\
@@ -436,7 +438,7 @@ __CONCAT(Xresume,irq_num): ;						\
 #else /* CPL_AND_CML */
 
 
-#define	INTR(irq_num, vec_name)						\
+#define	INTR(irq_num, vec_name, maybe_extra_ipending)			\
 	.text ;								\
 	SUPERALIGN_TEXT ;						\
 /* _XintrNN: entry point used by IDT/HWIs & splz_unpend via _vec[]. */	\
@@ -447,6 +449,8 @@ IDTVEC(vec_name) ;							\
 	movl	%ax, %es ;						\
 	movl	$KPSEL, %eax ;						\
 	movl	%ax, %fs ;						\
+;									\
+	maybe_extra_ipending ;						\
 ;									\
 	APIC_ITRACE(apic_itrace_enter, irq_num, APIC_ITRACE_ENTER) ;	\
 	lock ;					/* MP-safe */		\
@@ -916,30 +920,31 @@ MCOUNT_LABEL(bintr)
 	FAST_INTR(21,fastintr21)
 	FAST_INTR(22,fastintr22)
 	FAST_INTR(23,fastintr23)
-	INTR(0,intr0)
-	INTR(1,intr1)
-	INTR(2,intr2)
-	INTR(3,intr3)
-	INTR(4,intr4)
-	INTR(5,intr5)
-	INTR(6,intr6)
-	INTR(7,intr7)
-	INTR(8,intr8)
-	INTR(9,intr9)
-	INTR(10,intr10)
-	INTR(11,intr11)
-	INTR(12,intr12)
-	INTR(13,intr13)
-	INTR(14,intr14)
-	INTR(15,intr15)
-	INTR(16,intr16)
-	INTR(17,intr17)
-	INTR(18,intr18)
-	INTR(19,intr19)
-	INTR(20,intr20)
-	INTR(21,intr21)
-	INTR(22,intr22)
-	INTR(23,intr23)
+#define	CLKINTR_PENDING	movl $1,CNAME(clkintr_pending)
+	INTR(0,intr0, CLKINTR_PENDING)
+	INTR(1,intr1,)
+	INTR(2,intr2,)
+	INTR(3,intr3,)
+	INTR(4,intr4,)
+	INTR(5,intr5,)
+	INTR(6,intr6,)
+	INTR(7,intr7,)
+	INTR(8,intr8,)
+	INTR(9,intr9,)
+	INTR(10,intr10,)
+	INTR(11,intr11,)
+	INTR(12,intr12,)
+	INTR(13,intr13,)
+	INTR(14,intr14,)
+	INTR(15,intr15,)
+	INTR(16,intr16,)
+	INTR(17,intr17,)
+	INTR(18,intr18,)
+	INTR(19,intr19,)
+	INTR(20,intr20,)
+	INTR(21,intr21,)
+	INTR(22,intr22,)
+	INTR(23,intr23,)
 MCOUNT_LABEL(eintr)
 
 	.data
diff --git a/sys/i386/i386/tsc.c b/sys/i386/i386/tsc.c
index d9ee00edd9a5..75511f411e12 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 1.132 1999/04/25 09:00:00 phk Exp $
+ *	$Id: clock.c,v 1.133 1999/05/09 23:32:29 peter Exp $
  */
 
 /*
@@ -69,6 +69,7 @@
 #include <machine/ipl.h>
 #include <machine/limits.h>
 #include <machine/md_var.h>
+#include <machine/psl.h>
 #if NAPM > 0
 #include <machine/apm_bios.h>
 #include <i386/apm/apm_setup.h>
@@ -127,6 +128,7 @@ static void setup_8254_mixed_mode __P((void));
 #define	TIMER0_MAX_FREQ		20000
 
 int	adjkerntz;		/* local offset from GMT in seconds */
+int	clkintr_pending;
 int	disable_rtc_set;	/* disable resettodr() if != 0 */
 volatile u_int	idelayed;
 int	statclock_disable;
@@ -199,24 +201,15 @@ static void
 clkintr(struct clockframe frame)
 {
 	if (timecounter->tc_get_timecount == i8254_get_timecount) {
-		/*
-		 * Maintain i8254_offset and related variables.  Optimize
-		 * the usual case where i8254 counter rollover has not been
-		 * detected in i8254_get_timecount() by pretending that we
-		 * read the counter when it rolled over.  Otherwise, call
-		 * i8254_get_timecount() to do most of the work.  The
-		 * hardware counter must be read to ensure monotonicity
-		 * despite multiple rollovers and misbehaving hardware.
-		 */
-		(disable_intr)();	/* XXX avoid clock locking */
-		if (i8254_ticked) {
-			i8254_get_timecount(NULL);
+		disable_intr();
+		if (i8254_ticked)
 			i8254_ticked = 0;
-		} else {
+		else {
 			i8254_offset += timer0_max_count;
 			i8254_lastcount = 0;
 		}
-		(enable_intr)();	/* XXX avoid clock locking */
+		clkintr_pending = 0;
+		enable_intr();
 	}
 	timer_func(&frame);
 	switch (timer0_state) {
@@ -1159,13 +1152,21 @@ i8254_get_timecount(struct timecounter *tc)
 
 	low = inb(TIMER_CNTR0);
 	high = inb(TIMER_CNTR0);
-
-	count = hardclock_max_count - ((high << 8) | low);
-	if (count < i8254_lastcount) {
+	count = timer0_max_count - ((high << 8) | low);
+	if (count < i8254_lastcount ||
+	    (!i8254_ticked && (clkintr_pending ||
+	    ((count < 20 || (!(ef & PSL_I) && count < timer0_max_count / 2u)) &&
+#ifdef APIC_IO
+#define	lapic_irr1	((volatile u_int *)&lapic)[0x210 / 4]	/* XXX XXX */
+	    /* XXX this assumes that apic_8254_intr is < 24. */
+	    (lapic_irr1 & (1 << apic_8254_intr))))
+#else
+	    (inb(IO_ICU1) & 1)))
+#endif
+	    )) {
 		i8254_ticked = 1;
-		i8254_offset += hardclock_max_count;
+		i8254_offset += timer0_max_count;
 	}
-
 	i8254_lastcount = count;
 	count += i8254_offset;
 	CLOCK_UNLOCK();
diff --git a/sys/i386/isa/apic_vector.s b/sys/i386/isa/apic_vector.s
index 88340e6626b6..66d53a6a2ce0 100644
--- a/sys/i386/isa/apic_vector.s
+++ b/sys/i386/isa/apic_vector.s
@@ -1,6 +1,6 @@
 /*
  *	from: vector.s, 386BSD 0.1 unknown origin
- *	$Id: apic_vector.s,v 1.36 1999/04/14 14:26:35 bde Exp $
+ *	$Id: apic_vector.s,v 1.37 1999/04/28 01:04:12 luoqi Exp $
  */
 
 
@@ -324,7 +324,7 @@ log_intr_event:
 		
 #ifdef CPL_AND_CML
 
-#define	INTR(irq_num, vec_name)						\
+#define	INTR(irq_num, vec_name, maybe_extra_ipending)			\
 	.text ;								\
 	SUPERALIGN_TEXT ;						\
 /* _XintrNN: entry point used by IDT/HWIs & splz_unpend via _vec[]. */	\
@@ -335,6 +335,8 @@ IDTVEC(vec_name) ;							\
 	movl	%ax, %es ;						\
 	movl	$KPSEL, %eax ;						\
 	movl	%ax, %fs ;						\
+;									\
+	maybe_extra_ipending ;						\
 ;									\
 	APIC_ITRACE(apic_itrace_enter, irq_num, APIC_ITRACE_ENTER) ;	\
 	lock ;					/* MP-safe */		\
@@ -436,7 +438,7 @@ __CONCAT(Xresume,irq_num): ;						\
 #else /* CPL_AND_CML */
 
 
-#define	INTR(irq_num, vec_name)						\
+#define	INTR(irq_num, vec_name, maybe_extra_ipending)			\
 	.text ;								\
 	SUPERALIGN_TEXT ;						\
 /* _XintrNN: entry point used by IDT/HWIs & splz_unpend via _vec[]. */	\
@@ -447,6 +449,8 @@ IDTVEC(vec_name) ;							\
 	movl	%ax, %es ;						\
 	movl	$KPSEL, %eax ;						\
 	movl	%ax, %fs ;						\
+;									\
+	maybe_extra_ipending ;						\
 ;									\
 	APIC_ITRACE(apic_itrace_enter, irq_num, APIC_ITRACE_ENTER) ;	\
 	lock ;					/* MP-safe */		\
@@ -916,30 +920,31 @@ MCOUNT_LABEL(bintr)
 	FAST_INTR(21,fastintr21)
 	FAST_INTR(22,fastintr22)
 	FAST_INTR(23,fastintr23)
-	INTR(0,intr0)
-	INTR(1,intr1)
-	INTR(2,intr2)
-	INTR(3,intr3)
-	INTR(4,intr4)
-	INTR(5,intr5)
-	INTR(6,intr6)
-	INTR(7,intr7)
-	INTR(8,intr8)
-	INTR(9,intr9)
-	INTR(10,intr10)
-	INTR(11,intr11)
-	INTR(12,intr12)
-	INTR(13,intr13)
-	INTR(14,intr14)
-	INTR(15,intr15)
-	INTR(16,intr16)
-	INTR(17,intr17)
-	INTR(18,intr18)
-	INTR(19,intr19)
-	INTR(20,intr20)
-	INTR(21,intr21)
-	INTR(22,intr22)
-	INTR(23,intr23)
+#define	CLKINTR_PENDING	movl $1,CNAME(clkintr_pending)
+	INTR(0,intr0, CLKINTR_PENDING)
+	INTR(1,intr1,)
+	INTR(2,intr2,)
+	INTR(3,intr3,)
+	INTR(4,intr4,)
+	INTR(5,intr5,)
+	INTR(6,intr6,)
+	INTR(7,intr7,)
+	INTR(8,intr8,)
+	INTR(9,intr9,)
+	INTR(10,intr10,)
+	INTR(11,intr11,)
+	INTR(12,intr12,)
+	INTR(13,intr13,)
+	INTR(14,intr14,)
+	INTR(15,intr15,)
+	INTR(16,intr16,)
+	INTR(17,intr17,)
+	INTR(18,intr18,)
+	INTR(19,intr19,)
+	INTR(20,intr20,)
+	INTR(21,intr21,)
+	INTR(22,intr22,)
+	INTR(23,intr23,)
 MCOUNT_LABEL(eintr)
 
 	.data
diff --git a/sys/i386/isa/atpic_vector.s b/sys/i386/isa/atpic_vector.s
index 446030303231..453f9d553b84 100644
--- a/sys/i386/isa/atpic_vector.s
+++ b/sys/i386/isa/atpic_vector.s
@@ -1,6 +1,6 @@
 /*
  *	from: vector.s, 386BSD 0.1 unknown origin
- *	$Id: icu_vector.s,v 1.10 1999/04/14 14:26:36 bde Exp $
+ *	$Id: icu_vector.s,v 1.11 1999/04/28 01:04:13 luoqi Exp $
  */
 
 /*
@@ -106,7 +106,7 @@ IDTVEC(vec_name) ; \
 	MEXITCOUNT ; \
 	jmp	_doreti
 
-#define	INTR(irq_num, vec_name, icu, enable_icus, reg) \
+#define	INTR(irq_num, vec_name, icu, enable_icus, reg, maybe_extra_ipending) \
 	.text ; \
 	SUPERALIGN_TEXT ; \
 IDTVEC(vec_name) ; \
@@ -120,6 +120,7 @@ IDTVEC(vec_name) ; \
 	movl	%ax,%ds ;	/* ... early for obsolete reasons */ \
 	movl	%ax,%es ; \
 	movl	%ax,%fs ; \
+	maybe_extra_ipending ; \
 	movb	_imen + IRQ_BYTE(irq_num),%al ; \
 	orb	$IRQ_BIT(irq_num),%al ; \
 	movb	%al,_imen + IRQ_BYTE(irq_num) ; \
@@ -180,22 +181,23 @@ MCOUNT_LABEL(bintr)
 	FAST_INTR(13,fastintr13, ENABLE_ICU1_AND_2)
 	FAST_INTR(14,fastintr14, ENABLE_ICU1_AND_2)
 	FAST_INTR(15,fastintr15, ENABLE_ICU1_AND_2)
-	INTR(0,intr0, IO_ICU1, ENABLE_ICU1, al)
-	INTR(1,intr1, IO_ICU1, ENABLE_ICU1, al)
-	INTR(2,intr2, IO_ICU1, ENABLE_ICU1, al)
-	INTR(3,intr3, IO_ICU1, ENABLE_ICU1, al)
-	INTR(4,intr4, IO_ICU1, ENABLE_ICU1, al)
-	INTR(5,intr5, IO_ICU1, ENABLE_ICU1, al)
-	INTR(6,intr6, IO_ICU1, ENABLE_ICU1, al)
-	INTR(7,intr7, IO_ICU1, ENABLE_ICU1, al)
-	INTR(8,intr8, IO_ICU2, ENABLE_ICU1_AND_2, ah)
-	INTR(9,intr9, IO_ICU2, ENABLE_ICU1_AND_2, ah)
-	INTR(10,intr10, IO_ICU2, ENABLE_ICU1_AND_2, ah)
-	INTR(11,intr11, IO_ICU2, ENABLE_ICU1_AND_2, ah)
-	INTR(12,intr12, IO_ICU2, ENABLE_ICU1_AND_2, ah)
-	INTR(13,intr13, IO_ICU2, ENABLE_ICU1_AND_2, ah)
-	INTR(14,intr14, IO_ICU2, ENABLE_ICU1_AND_2, ah)
-	INTR(15,intr15, IO_ICU2, ENABLE_ICU1_AND_2, ah)
+#define	CLKINTR_PENDING	movl $1,CNAME(clkintr_pending)
+	INTR(0,intr0, IO_ICU1, ENABLE_ICU1, al, CLKINTR_PENDING)
+	INTR(1,intr1, IO_ICU1, ENABLE_ICU1, al,)
+	INTR(2,intr2, IO_ICU1, ENABLE_ICU1, al,)
+	INTR(3,intr3, IO_ICU1, ENABLE_ICU1, al,)
+	INTR(4,intr4, IO_ICU1, ENABLE_ICU1, al,)
+	INTR(5,intr5, IO_ICU1, ENABLE_ICU1, al,)
+	INTR(6,intr6, IO_ICU1, ENABLE_ICU1, al,)
+	INTR(7,intr7, IO_ICU1, ENABLE_ICU1, al,)
+	INTR(8,intr8, IO_ICU2, ENABLE_ICU1_AND_2, ah,)
+	INTR(9,intr9, IO_ICU2, ENABLE_ICU1_AND_2, ah,)
+	INTR(10,intr10, IO_ICU2, ENABLE_ICU1_AND_2, ah,)
+	INTR(11,intr11, IO_ICU2, ENABLE_ICU1_AND_2, ah,)
+	INTR(12,intr12, IO_ICU2, ENABLE_ICU1_AND_2, ah,)
+	INTR(13,intr13, IO_ICU2, ENABLE_ICU1_AND_2, ah,)
+	INTR(14,intr14, IO_ICU2, ENABLE_ICU1_AND_2, ah,)
+	INTR(15,intr15, IO_ICU2, ENABLE_ICU1_AND_2, ah,)
 MCOUNT_LABEL(eintr)
 
 	.data
diff --git a/sys/i386/isa/clock.c b/sys/i386/isa/clock.c
index d9ee00edd9a5..75511f411e12 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 1.132 1999/04/25 09:00:00 phk Exp $
+ *	$Id: clock.c,v 1.133 1999/05/09 23:32:29 peter Exp $
  */
 
 /*
@@ -69,6 +69,7 @@
 #include <machine/ipl.h>
 #include <machine/limits.h>
 #include <machine/md_var.h>
+#include <machine/psl.h>
 #if NAPM > 0
 #include <machine/apm_bios.h>
 #include <i386/apm/apm_setup.h>
@@ -127,6 +128,7 @@ static void setup_8254_mixed_mode __P((void));
 #define	TIMER0_MAX_FREQ		20000
 
 int	adjkerntz;		/* local offset from GMT in seconds */
+int	clkintr_pending;
 int	disable_rtc_set;	/* disable resettodr() if != 0 */
 volatile u_int	idelayed;
 int	statclock_disable;
@@ -199,24 +201,15 @@ static void
 clkintr(struct clockframe frame)
 {
 	if (timecounter->tc_get_timecount == i8254_get_timecount) {
-		/*
-		 * Maintain i8254_offset and related variables.  Optimize
-		 * the usual case where i8254 counter rollover has not been
-		 * detected in i8254_get_timecount() by pretending that we
-		 * read the counter when it rolled over.  Otherwise, call
-		 * i8254_get_timecount() to do most of the work.  The
-		 * hardware counter must be read to ensure monotonicity
-		 * despite multiple rollovers and misbehaving hardware.
-		 */
-		(disable_intr)();	/* XXX avoid clock locking */
-		if (i8254_ticked) {
-			i8254_get_timecount(NULL);
+		disable_intr();
+		if (i8254_ticked)
 			i8254_ticked = 0;
-		} else {
+		else {
 			i8254_offset += timer0_max_count;
 			i8254_lastcount = 0;
 		}
-		(enable_intr)();	/* XXX avoid clock locking */
+		clkintr_pending = 0;
+		enable_intr();
 	}
 	timer_func(&frame);
 	switch (timer0_state) {
@@ -1159,13 +1152,21 @@ i8254_get_timecount(struct timecounter *tc)
 
 	low = inb(TIMER_CNTR0);
 	high = inb(TIMER_CNTR0);
-
-	count = hardclock_max_count - ((high << 8) | low);
-	if (count < i8254_lastcount) {
+	count = timer0_max_count - ((high << 8) | low);
+	if (count < i8254_lastcount ||
+	    (!i8254_ticked && (clkintr_pending ||
+	    ((count < 20 || (!(ef & PSL_I) && count < timer0_max_count / 2u)) &&
+#ifdef APIC_IO
+#define	lapic_irr1	((volatile u_int *)&lapic)[0x210 / 4]	/* XXX XXX */
+	    /* XXX this assumes that apic_8254_intr is < 24. */
+	    (lapic_irr1 & (1 << apic_8254_intr))))
+#else
+	    (inb(IO_ICU1) & 1)))
+#endif
+	    )) {
 		i8254_ticked = 1;
-		i8254_offset += hardclock_max_count;
+		i8254_offset += timer0_max_count;
 	}
-
 	i8254_lastcount = count;
 	count += i8254_offset;
 	CLOCK_UNLOCK();
diff --git a/sys/i386/isa/icu_vector.s b/sys/i386/isa/icu_vector.s
index 446030303231..453f9d553b84 100644
--- a/sys/i386/isa/icu_vector.s
+++ b/sys/i386/isa/icu_vector.s
@@ -1,6 +1,6 @@
 /*
  *	from: vector.s, 386BSD 0.1 unknown origin
- *	$Id: icu_vector.s,v 1.10 1999/04/14 14:26:36 bde Exp $
+ *	$Id: icu_vector.s,v 1.11 1999/04/28 01:04:13 luoqi Exp $
  */
 
 /*
@@ -106,7 +106,7 @@ IDTVEC(vec_name) ; \
 	MEXITCOUNT ; \
 	jmp	_doreti
 
-#define	INTR(irq_num, vec_name, icu, enable_icus, reg) \
+#define	INTR(irq_num, vec_name, icu, enable_icus, reg, maybe_extra_ipending) \
 	.text ; \
 	SUPERALIGN_TEXT ; \
 IDTVEC(vec_name) ; \
@@ -120,6 +120,7 @@ IDTVEC(vec_name) ; \
 	movl	%ax,%ds ;	/* ... early for obsolete reasons */ \
 	movl	%ax,%es ; \
 	movl	%ax,%fs ; \
+	maybe_extra_ipending ; \
 	movb	_imen + IRQ_BYTE(irq_num),%al ; \
 	orb	$IRQ_BIT(irq_num),%al ; \
 	movb	%al,_imen + IRQ_BYTE(irq_num) ; \
@@ -180,22 +181,23 @@ MCOUNT_LABEL(bintr)
 	FAST_INTR(13,fastintr13, ENABLE_ICU1_AND_2)
 	FAST_INTR(14,fastintr14, ENABLE_ICU1_AND_2)
 	FAST_INTR(15,fastintr15, ENABLE_ICU1_AND_2)
-	INTR(0,intr0, IO_ICU1, ENABLE_ICU1, al)
-	INTR(1,intr1, IO_ICU1, ENABLE_ICU1, al)
-	INTR(2,intr2, IO_ICU1, ENABLE_ICU1, al)
-	INTR(3,intr3, IO_ICU1, ENABLE_ICU1, al)
-	INTR(4,intr4, IO_ICU1, ENABLE_ICU1, al)
-	INTR(5,intr5, IO_ICU1, ENABLE_ICU1, al)
-	INTR(6,intr6, IO_ICU1, ENABLE_ICU1, al)
-	INTR(7,intr7, IO_ICU1, ENABLE_ICU1, al)
-	INTR(8,intr8, IO_ICU2, ENABLE_ICU1_AND_2, ah)
-	INTR(9,intr9, IO_ICU2, ENABLE_ICU1_AND_2, ah)
-	INTR(10,intr10, IO_ICU2, ENABLE_ICU1_AND_2, ah)
-	INTR(11,intr11, IO_ICU2, ENABLE_ICU1_AND_2, ah)
-	INTR(12,intr12, IO_ICU2, ENABLE_ICU1_AND_2, ah)
-	INTR(13,intr13, IO_ICU2, ENABLE_ICU1_AND_2, ah)
-	INTR(14,intr14, IO_ICU2, ENABLE_ICU1_AND_2, ah)
-	INTR(15,intr15, IO_ICU2, ENABLE_ICU1_AND_2, ah)
+#define	CLKINTR_PENDING	movl $1,CNAME(clkintr_pending)
+	INTR(0,intr0, IO_ICU1, ENABLE_ICU1, al, CLKINTR_PENDING)
+	INTR(1,intr1, IO_ICU1, ENABLE_ICU1, al,)
+	INTR(2,intr2, IO_ICU1, ENABLE_ICU1, al,)
+	INTR(3,intr3, IO_ICU1, ENABLE_ICU1, al,)
+	INTR(4,intr4, IO_ICU1, ENABLE_ICU1, al,)
+	INTR(5,intr5, IO_ICU1, ENABLE_ICU1, al,)
+	INTR(6,intr6, IO_ICU1, ENABLE_ICU1, al,)
+	INTR(7,intr7, IO_ICU1, ENABLE_ICU1, al,)
+	INTR(8,intr8, IO_ICU2, ENABLE_ICU1_AND_2, ah,)
+	INTR(9,intr9, IO_ICU2, ENABLE_ICU1_AND_2, ah,)
+	INTR(10,intr10, IO_ICU2, ENABLE_ICU1_AND_2, ah,)
+	INTR(11,intr11, IO_ICU2, ENABLE_ICU1_AND_2, ah,)
+	INTR(12,intr12, IO_ICU2, ENABLE_ICU1_AND_2, ah,)
+	INTR(13,intr13, IO_ICU2, ENABLE_ICU1_AND_2, ah,)
+	INTR(14,intr14, IO_ICU2, ENABLE_ICU1_AND_2, ah,)
+	INTR(15,intr15, IO_ICU2, ENABLE_ICU1_AND_2, ah,)
 MCOUNT_LABEL(eintr)
 
 	.data
diff --git a/sys/isa/atrtc.c b/sys/isa/atrtc.c
index d9ee00edd9a5..75511f411e12 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 1.132 1999/04/25 09:00:00 phk Exp $
+ *	$Id: clock.c,v 1.133 1999/05/09 23:32:29 peter Exp $
  */
 
 /*
@@ -69,6 +69,7 @@
 #include <machine/ipl.h>
 #include <machine/limits.h>
 #include <machine/md_var.h>
+#include <machine/psl.h>
 #if NAPM > 0
 #include <machine/apm_bios.h>
 #include <i386/apm/apm_setup.h>
@@ -127,6 +128,7 @@ static void setup_8254_mixed_mode __P((void));
 #define	TIMER0_MAX_FREQ		20000
 
 int	adjkerntz;		/* local offset from GMT in seconds */
+int	clkintr_pending;
 int	disable_rtc_set;	/* disable resettodr() if != 0 */
 volatile u_int	idelayed;
 int	statclock_disable;
@@ -199,24 +201,15 @@ static void
 clkintr(struct clockframe frame)
 {
 	if (timecounter->tc_get_timecount == i8254_get_timecount) {
-		/*
-		 * Maintain i8254_offset and related variables.  Optimize
-		 * the usual case where i8254 counter rollover has not been
-		 * detected in i8254_get_timecount() by pretending that we
-		 * read the counter when it rolled over.  Otherwise, call
-		 * i8254_get_timecount() to do most of the work.  The
-		 * hardware counter must be read to ensure monotonicity
-		 * despite multiple rollovers and misbehaving hardware.
-		 */
-		(disable_intr)();	/* XXX avoid clock locking */
-		if (i8254_ticked) {
-			i8254_get_timecount(NULL);
+		disable_intr();
+		if (i8254_ticked)
 			i8254_ticked = 0;
-		} else {
+		else {
 			i8254_offset += timer0_max_count;
 			i8254_lastcount = 0;
 		}
-		(enable_intr)();	/* XXX avoid clock locking */
+		clkintr_pending = 0;
+		enable_intr();
 	}
 	timer_func(&frame);
 	switch (timer0_state) {
@@ -1159,13 +1152,21 @@ i8254_get_timecount(struct timecounter *tc)
 
 	low = inb(TIMER_CNTR0);
 	high = inb(TIMER_CNTR0);
-
-	count = hardclock_max_count - ((high << 8) | low);
-	if (count < i8254_lastcount) {
+	count = timer0_max_count - ((high << 8) | low);
+	if (count < i8254_lastcount ||
+	    (!i8254_ticked && (clkintr_pending ||
+	    ((count < 20 || (!(ef & PSL_I) && count < timer0_max_count / 2u)) &&
+#ifdef APIC_IO
+#define	lapic_irr1	((volatile u_int *)&lapic)[0x210 / 4]	/* XXX XXX */
+	    /* XXX this assumes that apic_8254_intr is < 24. */
+	    (lapic_irr1 & (1 << apic_8254_intr))))
+#else
+	    (inb(IO_ICU1) & 1)))
+#endif
+	    )) {
 		i8254_ticked = 1;
-		i8254_offset += hardclock_max_count;
+		i8254_offset += timer0_max_count;
 	}
-
 	i8254_lastcount = count;
 	count += i8254_offset;
 	CLOCK_UNLOCK();