+# define TICK_FREQUENCY 50 /* ticks per second */
+# define TICK_MILLISECS (1000/TICK_FREQUENCY) /* ms per tick */
+
+/* Context switch timing constants. Context switches happen after a
+ * whole number of ticks, the default being every tick.
+ */
+#define CS_MIN_MILLISECS TICK_MILLISECS /* milliseconds per slice */
+
+extern rtsBool do_prof_ticks; /* profiling ticks on/off */
+