--- kern_clock.c.dist	2008-10-12 10:49:37.000000000 +0100
+++ kern_clock.c	2009-02-11 21:54:21.000000000 +0000
@@ -220,6 +220,8 @@
 
 	if (CPU_IS_PRIMARY(ci)) {
 		hardclock_ticks++;
+		if ((hardclock_ticks % (60*hz)) == 0)
+			Debugger();
 		tc_ticktock();
 	}