diff --git a/build/shared/revisions.txt b/build/shared/revisions.txt
index 024b44377..dbea406ca 100644
--- a/build/shared/revisions.txt
+++ b/build/shared/revisions.txt
@@ -1,8 +1,12 @@
 
 ARDUINO 1.5.3 BETA
 
+[ide]
 * Removed useless baud rates from serial monitor
 
+[arduino core]
+* sam: Fixed delayMicrosecond() when interrupts are disabled
+
 ARDUINO 1.5.2 BETA - 2013.02.06
 
 [ide]
diff --git a/hardware/arduino/sam/cores/arduino/Arduino.h b/hardware/arduino/sam/cores/arduino/Arduino.h
index c433ead6a..a1682a36c 100644
--- a/hardware/arduino/sam/cores/arduino/Arduino.h
+++ b/hardware/arduino/sam/cores/arduino/Arduino.h
@@ -41,12 +41,6 @@ extern "C"{
 
 void yield(void);
 
-#include "wiring.h"
-#include "wiring_digital.h"
-#include "wiring_analog.h"
-#include "wiring_shift.h"
-#include "WInterrupts.h"
-
 /* sketch */
 extern void setup( void ) ;
 extern void loop( void ) ;
@@ -195,6 +189,12 @@ extern const PinDescription g_APinDescription[] ;
 // Include board variant
 #include "variant.h"
 
+#include "wiring.h"
+#include "wiring_digital.h"
+#include "wiring_analog.h"
+#include "wiring_shift.h"
+#include "WInterrupts.h"
+
 // USB Device
 #define USB_VID            0x2341 // arduino LLC vid
 #define USB_PID_LEONARDO   0x0034
diff --git a/hardware/arduino/sam/cores/arduino/wiring.c b/hardware/arduino/sam/cores/arduino/wiring.c
index 431761b44..a934c50f5 100644
--- a/hardware/arduino/sam/cores/arduino/wiring.c
+++ b/hardware/arduino/sam/cores/arduino/wiring.c
@@ -49,13 +49,6 @@ void delay( uint32_t ms )
     	yield();
 }
 
-void delayMicroseconds( uint32_t us )
-{
-    uint32_t start = micros();
-    while ((micros() - start) < us)
-        ;
-}
-
 #if defined ( __ICCARM__ ) /* IAR Ewarm 5.41+ */
 extern signed int putchar( signed int c ) ;
 /**
diff --git a/hardware/arduino/sam/cores/arduino/wiring.h b/hardware/arduino/sam/cores/arduino/wiring.h
index ad13cac66..3c58cf06c 100644
--- a/hardware/arduino/sam/cores/arduino/wiring.h
+++ b/hardware/arduino/sam/cores/arduino/wiring.h
@@ -62,8 +62,16 @@ extern void delay( uint32_t dwMs ) ;
  *
  * \param dwUs the number of microseconds to pause (uint32_t)
  */
-extern void delayMicroseconds( uint32_t dwUs ) ;
-
+static inline void delayMicroseconds(uint32_t) __attribute__((always_inline, unused));
+static inline void delayMicroseconds(uint32_t usec){
+    uint32_t n = usec * (VARIANT_MCK / 3000000);
+    asm volatile(
+        "L_%=_delayMicroseconds:"       "\n\t"
+        "subs   %0, #1"                 "\n\t"
+        "bge    L_%=_delayMicroseconds" "\n"
+        : "+r" (n) :
+    );
+}
 
 #ifdef __cplusplus
 }
diff --git a/hardware/arduino/sam/variants/arduino_due_x/variant.h b/hardware/arduino/sam/variants/arduino_due_x/variant.h
index 11893cfe8..d34a656d2 100644
--- a/hardware/arduino/sam/variants/arduino_due_x/variant.h
+++ b/hardware/arduino/sam/variants/arduino_due_x/variant.h
@@ -19,6 +19,16 @@
 #ifndef _VARIANT_ARDUINO_DUE_X_
 #define _VARIANT_ARDUINO_DUE_X_
 
+/*----------------------------------------------------------------------------
+ *        Definitions
+ *----------------------------------------------------------------------------*/
+
+/** Frequency of the board main oscillator */
+#define VARIANT_MAINOSC		12000000
+
+/** Master clock frequency */
+#define VARIANT_MCK			84000000
+
 /*----------------------------------------------------------------------------
  *        Headers
  *----------------------------------------------------------------------------*/
@@ -40,23 +50,6 @@ extern "C"{
 #    include <syscalls.h> /** RedHat Newlib minimal stub */
 #endif
 
-/*----------------------------------------------------------------------------
- *        Definitions
- *----------------------------------------------------------------------------*/
-
-/*----------------------------------------------------------------------------*/
-
-#define ArduinoDueX_DevEd
-
-/** Name of the board */
-#define VARIANT_NAME		"Arduino_DueX_Dev_Ed"
-
-/** Frequency of the board main oscillator */
-#define VARIANT_MAINOSC		12000000
-
-/** Master clock frequency */
-#define VARIANT_MCK			84000000
-
 /*----------------------------------------------------------------------------
  *        Pins
  *----------------------------------------------------------------------------*/