diff --git a/ChangeLog b/ChangeLog
index 416f4787316..4280c0b611c 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -161,6 +161,8 @@
 	* sched/usleep.c: Fixed nsec calculation
 	* lib/lib_strcspn.c: Function incorrectly named strspn().
 	* examples/ostest/main.c:  Errors in SDCC version of a memcpy() call
-	* examples/ostest/sighandl.c: Don't call fflush() if streams are disabled
+	* examples/ostest/sighand.c: Don't call fflush() if streams are disabled
+	* include/limits.h, include/time.h, sched/clock_internal.h: A support for
+	  using selectable system timer frequency.
 	* Started m68322
 
diff --git a/Documentation/NuttX.html b/Documentation/NuttX.html
index c6800174287..6b5d03248cb 100644
--- a/Documentation/NuttX.html
+++ b/Documentation/NuttX.html
@@ -8,7 +8,7 @@
   <tr align="center" bgcolor="#e4e4e4">
     <td>
       <h1><big><font color="#3c34ec"><i>NuttX RTOS</i></font></big></h1>
-      <p>Last Updated: May 26, 2007</p>
+      <p>Last Updated: June 9, 2007</p>
     </td>
   </tr>
 </table>
@@ -595,7 +595,9 @@ Other memory:
 	* sched/usleep.c: Fixed nsec calculation
 	* lib/lib_strcspn.c: Function incorrectly named strspn().
 	* examples/ostest/main.c:  Errors in SDCC version of a memcpy() call
-	* examples/ostest/sighandl.c: Don't call fflush() if streams are disabled
+	* examples/ostest/sighand.c: Don't call fflush() if streams are disabled
+	* include/limits.h, include/time.h, sched/clock_internal.h: A support for
+	  using selectable system timer frequency.
 	* Started m68322
 </pre></ul>
 
diff --git a/Documentation/NuttxPortingGuide.html b/Documentation/NuttxPortingGuide.html
index 8cd9d06e366..38ab0c31e99 100644
--- a/Documentation/NuttxPortingGuide.html
+++ b/Documentation/NuttxPortingGuide.html
@@ -1163,6 +1163,12 @@ The system can be re-made subsequently by just typing <code>make</code>.
     number of memory regions that the memory manager must
     handle and enables the API mm_addregion(start, end);
   </li>
+  <li>
+    <code>CONFIG_TICKS_PER_MSEC</code>: The default system timer is 100Hz
+    or <code>TICKS_PER_MSEC</code>=10.  This setting may be defined to inform NuttX
+    that the processor hardware is providing system timer interrupts at some interrupt
+    interval other than 10 msec.
+  </li>
   <li>
     <code>CONFIG_RR_INTERVAL</code>: The round robin timeslice will be set
     this number of milliseconds;  Round robin scheduling can
diff --git a/TODO b/TODO
index 0f16e150f03..3c5a1e83eca 100644
--- a/TODO
+++ b/TODO
@@ -7,10 +7,6 @@ o Task/Scheduler
 - Implement sys/mman.h and functions
 - Implement sys/wait.h and functions
 - Implement priority inheritance
-- Make the system timer frequency configurable via defconfig.  See:
-   _POSIX_CLOCKRES_MIN in limits.h
-   CLK_TCK in time.h
-   MSEC_PER_TICK in sched/clock_internal.h
 - Consider implementing wait, waitpid, waitid.  At present, a parent has
   no information about child tasks.
 - Several APIs do not set errno.  Need to review all APIs.
diff --git a/configs/README.txt b/configs/README.txt
index 77d41e13192..a123a1f0157 100644
--- a/configs/README.txt
+++ b/configs/README.txt
@@ -132,6 +132,11 @@ defconfig -- This is a configuration file similar to the Linux
 		  regions of memory to allocate from, this specifies the
 		  number of memory regions that the memory manager must
 		  handle and enables the API mm_addregion(start, end);
+		CONFIG_TICKS_PER_MSEC - The default system timer is 100Hz
+		  or TICKS_PER_MSEC=10.  This setting may be defined to
+		  inform NuttX that the processor hardware is providing
+		  system timer interrupts at some interrupt interval other
+		  than 10 msec.
 		CONFIG_RR_INTERVAL - The round robin timeslice will be set
 		  this number of milliseconds;  Round robin scheduling can
 		  be disabled by setting this value to zero.
diff --git a/configs/c5471evm/defconfig b/configs/c5471evm/defconfig
index a534ae283fc..e247d9e87ce 100644
--- a/configs/c5471evm/defconfig
+++ b/configs/c5471evm/defconfig
@@ -109,6 +109,11 @@ CONFIG_UART_MODEM_2STOP=0
 #   handle and enables the API mm_addregion(start, end);
 # CONFIG_HAVE_LOWPUTC - architecture supports low-level, boot
 #   time console output
+# CONFIG_TICKS_PER_MSEC - The default system timer is 100Hz
+#   or TICKS_PER_MSEC=10.  This setting may be defined to
+#   inform NuttX that the processor hardware is providing
+#   system timer interrupts at some interrupt interval other
+#   than 10 msec.
 # CONFIG_RR_INTERVAL - The round robin timeslice will be set
 #   this number of milliseconds;  Round robin scheduling can
 #   be disabled by setting this value to zero.
diff --git a/configs/m68332evb/defconfig b/configs/m68332evb/defconfig
index 2df6f2e516d..2185e760a24 100644
--- a/configs/m68332evb/defconfig
+++ b/configs/m68332evb/defconfig
@@ -98,6 +98,11 @@ CONFIG_UART1_2STOP=0
 #   handle and enables the API mm_addregion(start, end);
 # CONFIG_HAVE_LOWPUTC - architecture supports low-level, boot
 #   time console output
+# CONFIG_TICKS_PER_MSEC - The default system timer is 100Hz
+#   or TICKS_PER_MSEC=10.  This setting may be defined to
+#   inform NuttX that the processor hardware is providing
+#   system timer interrupts at some interrupt interval other
+#   than 10 msec.
 # CONFIG_RR_INTERVAL - The round robin timeslice will be set
 #   this number of milliseconds;  Round robin scheduling can
 #   be disabled by setting this value to zero.
diff --git a/configs/mcu123-lpc214x/defconfig b/configs/mcu123-lpc214x/defconfig
index e9e97326b25..ca0c9a15337 100644
--- a/configs/mcu123-lpc214x/defconfig
+++ b/configs/mcu123-lpc214x/defconfig
@@ -122,6 +122,11 @@ CONFIG_UART1_2STOP=0
 #   handle and enables the API mm_addregion(start, end);
 # CONFIG_HAVE_LOWPUTC - architecture supports low-level, boot
 #   time console output
+# CONFIG_TICKS_PER_MSEC - The default system timer is 100Hz
+#   or TICKS_PER_MSEC=10.  This setting may be defined to
+#   inform NuttX that the processor hardware is providing
+#   system timer interrupts at some interrupt interval other
+#   than 10 msec.
 # CONFIG_RR_INTERVAL - The round robin timeslice will be set
 #   this number of milliseconds;  Round robin scheduling can
 #   be disabled by setting this value to zero.
diff --git a/configs/ntosd-dm320/defconfig b/configs/ntosd-dm320/defconfig
index aa6270250f3..640783cf1df 100644
--- a/configs/ntosd-dm320/defconfig
+++ b/configs/ntosd-dm320/defconfig
@@ -107,6 +107,11 @@ CONFIG_UART1_2STOP=0
 #   handle and enables the API mm_addregion(start, end);
 # CONFIG_HAVE_LOWPUTC - architecture supports low-level, boot
 #   time console output
+# CONFIG_TICKS_PER_MSEC - The default system timer is 100Hz
+#   or TICKS_PER_MSEC=10.  This setting may be defined to
+#   inform NuttX that the processor hardware is providing
+#   system timer interrupts at some interrupt interval other
+#   than 10 msec.
 # CONFIG_RR_INTERVAL - The round robin timeslice will be set
 #   this number of milliseconds;  Round robin scheduling can
 #   be disabled by setting this value to zero.
diff --git a/configs/pjrc-8051/defconfig b/configs/pjrc-8051/defconfig
index bc6084f0bfa..c9b8a481a33 100644
--- a/configs/pjrc-8051/defconfig
+++ b/configs/pjrc-8051/defconfig
@@ -95,6 +95,11 @@ CONFIG_LED_DEBUG=n
 #   handle and enables the API mm_addregion(start, end);
 # CONFIG_HAVE_LOWPUTC - architecture supports low-level, boot
 #   time console output
+# CONFIG_TICKS_PER_MSEC - The default system timer is 100Hz
+#   or TICKS_PER_MSEC=10.  This setting may be defined to
+#   inform NuttX that the processor hardware is providing
+#   system timer interrupts at some interrupt interval other
+#   than 10 msec.
 # CONFIG_RR_INTERVAL - The round robin timeslice will be set
 #   this number of milliseconds;  Round robin scheduling can
 #   be disabled by setting this value to zero.
diff --git a/configs/sim/defconfig b/configs/sim/defconfig
index 59f05d4ac1d..e5940848ea2 100644
--- a/configs/sim/defconfig
+++ b/configs/sim/defconfig
@@ -63,6 +63,11 @@ CONFIG_ARCH_BOARD_SIM=y
 #   handle and enables the API mm_addregion(start, end);
 # CONFIG_HAVE_LOWPUTC - architecture supports low-level, boot
 #   time console output
+# CONFIG_TICKS_PER_MSEC - The default system timer is 100Hz
+#   or TICKS_PER_MSEC=10.  This setting may be defined to
+#   inform NuttX that the processor hardware is providing
+#   system timer interrupts at some interrupt interval other
+#   than 10 msec.
 # CONFIG_RR_INTERVAL - The round robin timeslice will be set
 #   this number of milliseconds;  Round robin scheduling can
 #   be disabled by setting this value to zero.
diff --git a/include/limits.h b/include/limits.h
index 285eea684fb..d32c7177a74 100644
--- a/include/limits.h
+++ b/include/limits.h
@@ -114,11 +114,27 @@
 #define _POSIX_RTSIG_MAX      31
 #define _POSIX_SIGQUEUE_MAX   32
 
-/* Required for POSIX timers */
+/* Required for POSIX timers.
+ *
+ * _POSIX_DELAYTIMER_MAX is the number of timer expiration overruns.
+ *
+ * _POSIX_TIMER_MAX is the per-process number of timers.
+ *
+ * _POSIX_CLOCKRES_MIN is the resolution of the CLOCK_REALTIME clock in nanoseconds.
+ * CLOCK_REALTIME is controlled by the NuttX system time.  The default value is the
+ * system timer which has a resolution of 10 milliseconds.  This default setting can
+ * be overridden by defining the clock interval in milliseconds as CONFIG_MSEC_PER_TICK
+ * in the board configuration file.
+ */
 
 #define _POSIX_DELAYTIMER_MAX 32
 #define _POSIX_TIMER_MAX      32
-#define _POSIX_CLOCKRES_MIN   10000000
+
+#ifdef CONFIG_MSEC_PER_TICK
+# define _POSIX_CLOCKRES_MIN  ((CONFIG_MSEC_PER_TICK)*1000000)
+#else
+# define _POSIX_CLOCKRES_MIN  (10*1000000)
+#endif
 
 /* Required for asynchronous I/O */
 
diff --git a/include/time.h b/include/time.h
index 7a973142336..92b849fbeb6 100644
--- a/include/time.h
+++ b/include/time.h
@@ -51,9 +51,16 @@
  * Definitions
  ********************************************************************************/
 
-/* Clock tick of the system */
+/* Clock tick of the system (frequency Hz).  The default value is 100Hz, but this
+ * default setting can be overridden by defining the clock interval in
+ * milliseconds as CONFIG_MSEC_PER_TICK in the board configuration file.
+ */
 
-#define CLK_TCK 100
+#ifdef CONFIG_MSEC_PER_TICK
+# define CLK_TCK (1000/CONFIG_MSEC_PER_TICK)
+#else
+# define CLK_TCK (100)
+#endif
 
 /* This is the only clock_id supported by the "Clock and Timer
  * Functions."
diff --git a/sched/clock_internal.h b/sched/clock_internal.h
index 85cb13f0652..2f7a9c783bf 100644
--- a/sched/clock_internal.h
+++ b/sched/clock_internal.h
@@ -40,6 +40,7 @@
  * Included Files
  ********************************************************************************/
 
+#include <nuttx/config.h>
 #include <sys/types.h>
 #include <nuttx/compiler.h>
 
@@ -56,7 +57,20 @@
 #define USEC_PER_MSEC               1000
 #define NSEC_PER_USEC               1000
 
-#define MSEC_PER_TICK                 10
+/* The interrupt interval of the system timer is given by MSEC_PER_TICK.  This
+ * is the expected number of milliseconds between calls from the processor-
+ * specific logic to sched_process_timer().  The default value of MSEC_PER_TICK
+ * is 10 milliseconds (100KHz).  However, this default setting can be overridden
+ * by defining the interval in milliseconds as CONFIG_MSEC_PER_TICK in the board
+ * configuration file.
+ */
+
+#ifdef CONFIG_MSEC_PER_TICK
+# define MSEC_PER_TICK        (CONFIG_MSEC_PER_TICK)
+#else
+# define MSEC_PER_TICK        (10)
+#endif
+
 #define USEC_PER_TICK         (MSEC_PER_TICK * USEC_PER_MSEC)
 #define NSEC_PER_TICK         (MSEC_PER_TICK * NSEC_PER_MSEC)
 #define TICK_PER_SEC          (MSEC_PER_SEC / MSEC_PER_TICK)
@@ -64,13 +78,15 @@
 #define MSEC2TICK(msec)       (((msec)+(MSEC_PER_TICK/2))/MSEC_PER_TICK)
 #define USEC2TICK(usec)       (((usec)+(USEC_PER_TICK/2))/USEC_PER_TICK)
 
-#define JD_OF_EPOCH   2440588    /* Julian Date of noon, J1970 */
+#define JD_OF_EPOCH           2440588    /* Julian Date of noon, J1970 */
 
 #ifdef CONFIG_JULIAN_TIME
-# define GREG_DUTC    -141427    /* Default is October 15, 1582 */
-# define GREG_YEAR       1582
-# define GREG_MONTH        10
-# define GREG_DAY          15
+
+# define GREG_DUTC           -141427    /* Default is October 15, 1582 */
+# define GREG_YEAR            1582
+# define GREG_MONTH           10
+# define GREG_DAY             15
+
 #endif /* CONFIG_JULIAN_TIME */
 
 /********************************************************************************