--- usr/src/sys/i386/isa/clock.c.orig	Tue Jun  4 17:49:33 2002
+++ usr/src/sys/i386/isa/clock.c	Tue Jun  4 17:49:05 2002
@@ -770,6 +770,23 @@
 	}
 
 	set_timer_freq(timer_freq, hz);
+
+        /*
+         * manual adjustment of the system clock with a fix correction-factor
+         * eg. in  /boot/loader.conf:
+         *   clock.i8254.adjust="993959" 
+         * necessary for some notebooks
+         */
+        {
+            int clock_adjust;
+            clock_adjust = 1e6;
+            TUNABLE_INT_FETCH("clock.i8254.adjust", &clock_adjust);
+            timer_freq *= clock_adjust / 1000000.0;
+            if (bootverbose)
+                printf("clock.adjust %d, i8254 clock: %u Hz\n", 
+                        clock_adjust, timer_freq);
+        }
+
 	i8254_timecounter.tc_frequency = timer_freq;
 	init_timecounter(&i8254_timecounter);