-# ifndef CLK_TCK
-# ifndef _BSD_CLK_TCK_ /* FreeBSD hack */
-# define HZ 100.0
-# else /* _BSD_CLK_TCK_ */
-# define HZ ((double)_BSD_CLK_TCK_)
+# if defined(_SC_CLK_TCK) \
+ && (!defined(OPENSSL_SYS_VMS) || __CTRL_VER >= 70000000)
+/* # define HZ ((double)sysconf(_SC_CLK_TCK)) */
+# define HZ sysconf(_SC_CLK_TCK)
+# else
+# ifndef CLK_TCK
+# ifndef _BSD_CLK_TCK_ /* FreeBSD hack */
+# define HZ 100.0
+# else /* _BSD_CLK_TCK_ */
+# define HZ ((double)_BSD_CLK_TCK_)
+# endif
+# else /* CLK_TCK */
+# define HZ ((double)CLK_TCK)