+#elif (AHZ % 512) == 0
+ x *= AHZ/512;
+ do_div(x, (NSEC_PER_SEC / 512));
+#else
+ /*
+ * max relative error 5.7e-8 (1.8s per year) for AHZ <= 1024,
+ * overflow after 64.99 years.
+ * exact for AHZ=60, 72, 90, 120, 144, 180, 300, 600, 900, ...
+ */
+ x *= 9;
+ do_div(x, (unsigned long)((9ull * NSEC_PER_SEC + (AHZ/2))
+ / AHZ));