diff --git a/arch/sim/src/up_idle.c b/arch/sim/src/up_idle.c
index 87b870e4cd..8d04000c4c 100644
--- a/arch/sim/src/up_idle.c
+++ b/arch/sim/src/up_idle.c
@@ -1,7 +1,7 @@
 /****************************************************************************
  * up_idle.c
  *
- *   Copyright (C) 2007-2009, 2011-2012 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2007-2009, 2011-2012, 2014 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <gnutt@nuttx.org>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -94,11 +94,17 @@ extern void up_x11update(void);
 
 void up_idle(void)
 {
+#ifdef CONFIG_SCHED_TICKLESS
+  /* Driver the simulated interval timer */
+
+  up_timer_update();
+#else
   /* If the system is idle, then process "fake" timer interrupts.
    * Hopefully, something will wake up.
    */
 
   sched_process_timer();
+#endif
 
   /* Run the network if enabled */
 
diff --git a/arch/sim/src/up_tickless.c b/arch/sim/src/up_tickless.c
new file mode 100644
index 0000000000..56202e7c1e
--- /dev/null
+++ b/arch/sim/src/up_tickless.c
@@ -0,0 +1,382 @@
+/****************************************************************************
+ * arch/sim/up_tickless.c
+ *
+ *   Copyright (C) 2014 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <gnutt@nuttx.org>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name NuttX nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+/****************************************************************************
+ * Tickless OS Support.
+ *
+ * When CONFIG_SCHED_TICKLESS is enabled, all support for timer interrupts
+ * is suppressed and the platform specific code is expected to provide the
+ * following custom functions.
+ *
+ *   void up_timer_initialize(void): Initializes the timer facilities.  Called
+ *     early in the intialization sequence (by up_intialize()).
+ *   int up_timer_gettime(FAR struct timespec *tp):  Returns the current
+ *     time from the platform specific time source.
+ *   int up_timer_cancel(void):  Cancels the interval timer.
+ *   int up_timer_start(FAR const struct timespec *tp): Start (or re-starts)
+ *     the interval timer.
+ *   int up_timer_resolution(FAR struct timespec *tp): Returns the
+ *     resolution of the interval timer.
+ *
+ * The RTOS will provide the following interfaces for use by the platform-
+ * specific interval timer implementation:
+ *
+ *   void sched_timer_expiration(void):  Called by the platform-specific
+ *     logic when the interval timer expires.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#include <stdint.h>
+#include <stdbool.h>
+#include <time.h>
+
+#include <nuttx/arch.h>
+
+#ifdef CONFIG_SCHED_TICKLESS
+
+/****************************************************************************
+ * Pre-processor Definitions
+ ****************************************************************************/
+
+#if defined(CONFIG_SIM_WALLTIME) || defined(CONFIG_SIM_X11FB)
+#  define TICK_USEC (1000000 / CLK_TCK)
+#  define TICK_SEC  (TICK_USEC / 1000000)
+#  define TICK_NSEC ((TICK_USEC % 1000) * 1000)
+#else
+#  define TICK_SEC 0
+#  define TICK_NSEC (128 * 1000)
+#endif
+
+/****************************************************************************
+ * Private Function Prototypes
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Data
+ ****************************************************************************/
+
+static struct timespec g_elapsed_time;
+static struct timespec g_interval_delay;
+static bool g_timer_active;
+
+/****************************************************************************
+ * Private Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: up_timer_initialize
+ *
+ * Description:
+ *   Initializes all platform-specific timer facilities.  This function is
+ *   called early in the initialization sequence by up_intialize().
+ *   On return, the current up-time should be available from
+ *   up_timer_gettime() and the interval timer is ready for use (but not
+ *   actively timing.
+ *
+ *   Provided by platform-specific code and called from the architecture-
+ *   specific logic.
+ *
+ * Input Parameters:
+ *   None
+ *
+ * Returned Value:
+ *   None
+ *
+ * Assumptions:
+ *   Called early in the initialization sequence before any special
+ *   concurrency protections are required.
+ *
+ ****************************************************************************/
+
+void up_timer_initialize(void)
+{
+}
+
+/****************************************************************************
+ * Name: up_timer_gettime
+ *
+ * Description:
+ *   Return the elapsed time since power-up (or, more correctly, since
+ *   up_timer_initialize() was called).  This function is functionally equivalent
+ *   to:
+ *
+ *      int clock_gettime(clockid_t clockid, FAR struct timespec *tp);
+ *
+ *   when clockid is CLOCK_MONOTONIC.
+ *
+ *   Provided by platform-specific code and called from the RTOS base code.
+ *
+ * Input Parameters:
+ *   tp - Provides the location in which to return the up-time.
+ *
+ * Returned Value:
+ *   Zero (OK) is returned on success; a negated errno value is returned on
+ *   any failure.
+ *
+ * Assumptions:
+ *   Called from the the normal tasking context.  The implementation must
+ *   provide whatever mutual exclusion is necessary for correct operation.
+ *   This can include disabling interrupts in order to assure atomic register
+ *   operations.
+ *
+ ****************************************************************************/
+
+int up_timer_gettime(FAR struct timespec *tp)
+{
+  tp->tv_sec  = g_elapsed_time.tv_sec;
+  tp->tv_nsec = g_elapsed_time.tv_nsec;
+  return OK;
+}
+
+/****************************************************************************
+ * Name: up_timer_cancel
+ *
+ * Description:
+ *   Cancel the interval timer.  up_timer_expiration() will not be called.
+ *
+ *   Provided by platform-specific code and called from the RTOS base code.
+ *
+ * Input Parameters:
+ *   None
+ *
+ * Returned Value:
+ *   Zero (OK) is returned on success; a negated errno value is returned on
+ *   any failure.
+ *
+ * Assumptions:
+ *   May be called from interrupt level handling or from the normal tasking
+ *   level.  Interrupts may need to be disabled internally to assure
+ *   non-reentrancy.
+ *
+ ****************************************************************************/
+
+#ifdef CONFIG_SCHED_TICKLESS
+int up_timer_cancel(void)
+{
+  g_interval_delay.tv_nsec = 0;
+  g_interval_delay.tv_sec  = 0;
+  g_timer_active           = false;
+}
+#endif
+
+/****************************************************************************
+ * Name: up_timer_start
+ *
+ * Description:
+ *   Start the interval timer.  up_timer_expiration() will be called at the
+ *   completion of the timeout (unless up_timer_cancel is called to stop
+ *   the timing.
+ *
+ *   Provided by platform-specific code and called from the RTOS base code.
+ *
+ * Input Parameters:
+ *   tp - Provides the time interval until up_timer_expiration() is called.
+ *
+ * Returned Value:
+ *   Zero (OK) is returned on success; a negated errno value is returned on
+ *   any failure.
+ *
+ * Assumptions:
+ *   May be called from interrupt level handling or from the normal tasking
+ *   level.  Interrupts may need to be disabled internally to assure
+ *   non-reentrancy.
+ *
+ ****************************************************************************/
+
+#ifdef CONFIG_SCHED_TICKLESS
+int up_timer_start(FAR const struct timespec *tp)
+{
+  g_interval_delay.tv_nsec = tp->tv_nsec;
+  g_interval_delay.tv_sec  = tp->tv_sec;
+  g_timer_active           = true;
+}
+#endif
+
+/****************************************************************************
+ * Name: up_timer_remaining
+ *
+ * Description:
+ *   Return the time remaining until the next timer expiratino.
+ *
+ *   Provided by platform-specific code and called from the RTOS base code.
+ *
+ * Input Parameters:
+ *   tp - Location to return the remaining time.  Zero should be returned
+ *        if the timer is not active.
+ *
+ * Returned Value:
+ *   Zero (OK) is returned on success; a negated errno value is returned on
+ *   any failure.
+ *
+ * Assumptions:
+ *   May be called from interrupt level handling or from the normal tasking
+ *   level.  Interrupts may need to be disabled internally to assure
+ *   non-reentrancy.
+ *
+ ****************************************************************************/
+
+int up_timer_remaining(FAR struct timespec *tp)
+{
+  if (g_timer_active)
+    {
+      tp->tv_sec  = g_interval_delay.tv_nsec;
+      tp->tv_nsec = g_interval_delay.tv_sec;
+    }
+  else
+    {
+      tp->tv_sec  = 0;
+      tp->tv_nsec = 0;
+    }
+
+  return OK;
+}
+
+/****************************************************************************
+ * Name: up_timer_resolution
+ *
+ * Description:
+ *   Returns the resolution of the interval timer.  This defines the minimal
+ *   time separation between two events and is used for scheduling and for
+ *   setting up timed events.
+ *
+ *   Provided by platform-specific code and called from the RTOS base code.
+ *
+ * Input Parameters:
+ *   tp - Provides the location in which to return the timer resolution.
+ *
+ * Returned Value:
+ *
+ * Assumptions:
+ *   May be called from interrupt level handling or from the normal tasking
+ *   level.  Interrupts may need to be disabled internally to assure
+ *   non-reentrancy.
+ *
+ ****************************************************************************/
+
+int up_timer_resolution(FAR struct timespec *tp)
+{
+  tp->tv_sec  = TICK_SEC;
+  tp->tv_nsec = TICK_NSEC;
+  return 0;
+}
+
+/****************************************************************************
+ * Name: up_timer_update
+ *
+ * Description:
+ *   Called from the IDLE loop to fake one timer tick.
+ *
+ * Input Parameters:
+ *   None
+ *
+ * Returned Value:
+ *   None
+ *
+ ****************************************************************************/
+
+void up_timer_update(void)
+{
+  /* Increment the elapsed time */
+
+  g_elapsed_time.tv_nsec += TICK_NSEC;
+  if (g_elapsed_time.tv_nsec >= 1000000000)
+    {
+      g_elapsed_time.tv_nsec++;
+      g_elapsed_time.tv_sec -= 1000000000;
+    }
+
+  g_elapsed_time.tv_sec += TICK_SEC;
+
+  /* Is the interval timer active? */
+
+  if (g_timer_active)
+    {
+      /* Yes... decrement the interval timer */
+
+      if (g_interval_delay.tv_sec < TICK_SEC)
+        {
+          /* No more seconds left... the timer has expired */
+
+          g_timer_active = false;
+          sched_timer_expiration();
+        }
+      else
+        {
+          /* Decrement seconds.  May decrement to zero */
+
+          g_interval_delay.tv_sec -= TICK_SEC;
+
+          /* Decrement nanoseconds */
+
+          if (g_interval_delay.tv_nsec > TICK_NSEC)
+            {
+              g_interval_delay.tv_nsec -= TICK_NSEC;
+            }
+
+          /* Handle borrow from seconds */
+
+          else if (g_interval_delay.tv_sec > 0)
+            {
+              if (g_interval_delay.tv_nsec >= TICK_NSEC)
+                {
+                  g_interval_delay.tv_nsec = 0;
+                }
+              else
+                {
+                  g_interval_delay.tv_sec--;
+                }
+            }
+
+          /* Otherwise the timer has expired */
+
+          else
+            {
+              g_timer_active = false;
+              sched_timer_expiration();
+            }
+        }
+    }
+}
+
+#endif /* CONFIG_SCHED_TICKLESS */