Index: sys/i386/isa/clock.c
===================================================================
--- sys/i386/isa/clock.c	(revision 212725)
+++ sys/i386/isa/clock.c	(working copy)
@@ -455,7 +455,16 @@
 	i8254_timecounter.tc_frequency = freq;
 	mtx_lock_spin(&clock_lock);
 	i8254_freq = freq;
-	if (using_lapic_timer != LAPIC_CLOCK_NONE)
+
+	/*
+	 * The lapic timer could not be available at very early boot stages.
+	 * As long as i8254 is used for calibrating other timers (the most
+	 * notably being TSC) in very early boot stages, avoid missing a
+	 * counter rollover by forcing full 16 bits.
+	 * If the lapic timer will not be available in the end, subsequent
+	 * calls to set_i8254_freq() will recalibrate the count.
+	 */
+	if (cold != 0 || using_lapic_timer != LAPIC_CLOCK_NONE)
 		new_i8254_real_max_count = 0x10000;
 	else
 		new_i8254_real_max_count = TIMER_DIV(intr_freq);
Index: sys/amd64/isa/clock.c
===================================================================
--- sys/amd64/isa/clock.c	(revision 212725)
+++ sys/amd64/isa/clock.c	(working copy)
@@ -426,7 +426,16 @@
 	i8254_timecounter.tc_frequency = freq;
 	mtx_lock_spin(&clock_lock);
 	i8254_freq = freq;
-	if (using_lapic_timer != LAPIC_CLOCK_NONE)
+
+	/*
+	 * The lapic timer could not be available at very early boot stages.
+	 * As long as i8254 is used for calibrating other timers (the most
+	 * notably being TSC) in very early boot stages, avoid missing a
+	 * counter rollover by forcing full 16 bits.
+	 * If the lapic timer will not be available in the end, subsequent
+	 * calls to set_i8254_freq() will recalibrate the count.
+	 */
+	if (cold != 0 || using_lapic_timer != LAPIC_CLOCK_NONE)
 		new_i8254_real_max_count = 0x10000;
 	else
 		new_i8254_real_max_count = TIMER_DIV(intr_freq);