diff --git a/arch/sim/src/sim/up_idle.c b/arch/sim/src/sim/up_idle.c
index 0dedbce8440..7e4a4d62088 100644
--- a/arch/sim/src/sim/up_idle.c
+++ b/arch/sim/src/sim/up_idle.c
@@ -26,7 +26,6 @@
 #include <debug.h>
 #include <nuttx/arch.h>
 #include <nuttx/power/pm.h>
-#include <nuttx/motor/foc/foc_dummy.h>
 
 #include "up_internal.h"
 
@@ -74,48 +73,9 @@ void up_idle(void)
     }
 #endif
 
-  /* Handle UART data availability */
-
-  up_uartloop();
-
-#if defined(CONFIG_SIM_TOUCHSCREEN) || defined(CONFIG_SIM_AJOYSTICK) || \
-    defined(CONFIG_SIM_BUTTONS)
-  /* Drive the X11 event loop */
-
-  up_x11events();
-#endif
-
-#ifdef CONFIG_SIM_NETDEV
-  /* Run the network if enabled */
-
-  netdriver_loop();
-#endif
-
-#ifdef CONFIG_SIM_NETUSRSOCK
-  usrsock_loop();
-#endif
-
-#ifdef CONFIG_RPTUN
-  up_rptun_loop();
-#endif
-
-#ifdef CONFIG_SIM_HCISOCKET
-  bthcisock_loop();
-#endif
-
-#ifdef CONFIG_SIM_SOUND
-  sim_audio_loop();
-#endif
-
 #ifdef CONFIG_ONESHOT
   /* Driver the simulated interval timer */
 
   up_timer_update();
 #endif
-
-#ifdef CONFIG_MOTOR_FOC_DUMMY
-  /* Update simulated FOC device */
-
-  foc_dummy_update();
-#endif
 }
diff --git a/arch/sim/src/sim/up_initialize.c b/arch/sim/src/sim/up_initialize.c
index 0e7fe717fc2..1d32e124db7 100644
--- a/arch/sim/src/sim/up_initialize.c
+++ b/arch/sim/src/sim/up_initialize.c
@@ -24,13 +24,17 @@
 
 #include <nuttx/config.h>
 
+#include <assert.h>
 #include <debug.h>
 
 #include <nuttx/arch.h>
 #include <nuttx/audio/audio.h>
+#include <nuttx/clock.h>
 #include <nuttx/drivers/drivers.h>
 #include <nuttx/fs/loop.h>
 #include <nuttx/fs/ioctl.h>
+#include <nuttx/kthread.h>
+#include <nuttx/motor/foc/foc_dummy.h>
 #include <nuttx/net/loopback.h>
 #include <nuttx/net/tun.h>
 #include <nuttx/net/telnet.h>
@@ -151,6 +155,70 @@ static void up_init_smartfs(void)
 }
 #endif
 
+static int up_loop_task(int argc, FAR char **argv)
+{
+  while (1)
+    {
+      /* Handle UART data availability */
+
+      up_uartloop();
+
+#if defined(CONFIG_SIM_TOUCHSCREEN) || defined(CONFIG_SIM_AJOYSTICK) || \
+    defined(CONFIG_SIM_BUTTONS)
+      /* Drive the X11 event loop */
+
+      up_x11events();
+#endif
+
+#ifdef CONFIG_SIM_NETDEV
+      /* Run the network if enabled */
+
+      netdriver_loop();
+#endif
+
+#ifdef CONFIG_SIM_NETUSRSOCK
+      usrsock_loop();
+#endif
+
+#ifdef CONFIG_RPTUN
+      up_rptun_loop();
+#endif
+
+#ifdef CONFIG_SIM_HCISOCKET
+      bthcisock_loop();
+#endif
+
+#ifdef CONFIG_SIM_SOUND
+      sim_audio_loop();
+#endif
+
+#ifdef CONFIG_MOTOR_FOC_DUMMY
+      /* Update simulated FOC device */
+
+      foc_dummy_update();
+#endif
+
+      /* Sleep minimal time, let the idle run */
+
+      usleep(USEC_PER_TICK);
+    }
+
+  return 0;
+}
+
+static void up_loop_init(void)
+{
+  int ret;
+
+  /* Use loop_task to simulate the IRQ */
+
+  ret = kthread_create("loop_task", 1,
+                       CONFIG_DEFAULT_TASK_STACKSIZE,
+                       up_loop_task, NULL);
+
+  DEBUGASSERT(ret > 0);
+}
+
 /****************************************************************************
  * Public Functions
  ****************************************************************************/
@@ -282,4 +350,6 @@ void up_initialize(void)
   audio_register("pcm0p", sim_audio_initialize(true));
   audio_register("pcm0c", sim_audio_initialize(false));
 #endif
+
+  up_loop_init();
 }
diff --git a/sched/init/nx_start.c b/sched/init/nx_start.c
index 74473e8f7a3..a17b97b2e11 100644
--- a/sched/init/nx_start.c
+++ b/sched/init/nx_start.c
@@ -609,6 +609,13 @@ void nx_start(void)
     }
 #endif
 
+  /* Disables context switching beacuse we need take the memory manager
+   * semaphore on this CPU so that it will not be available on the other
+   * CPUs until we have finished initialization.
+   */
+
+  sched_lock();
+
   /* Initialize the file system (needed to support device drivers) */
 
   fs_initialize();
@@ -746,13 +753,6 @@ void nx_start(void)
 
   syslog_initialize();
 
-  /* Disables context switching beacuse we need take the memory manager
-   * semaphore on this CPU so that it will not be available on the other
-   * CPUs until we have finished initialization.
-   */
-
-  sched_lock();
-
 #ifdef CONFIG_SMP
   /* Start all CPUs *********************************************************/