diff --git a/demos/MSP430-MSP430x1611-GCC/board.c b/demos/MSP430-MSP430x1611-GCC/board.c
index 8fcecec17..f5e5e4012 100644
--- a/demos/MSP430-MSP430x1611-GCC/board.c
+++ b/demos/MSP430-MSP430x1611-GCC/board.c
@@ -85,9 +85,13 @@ void hwinit(void) {
   InitSerial();
 }
 
-interrupt(TIMERA0_VECTOR) tmr0irq(void) {
+SYS_IRQ_HANDLER(TIMERA0_VECTOR) tmr0irq(void) {
 
-  chSysIRQEnterI();
+  SYS_IRQ_PROLOGUE();
+
+  chSysLockI();
   chSysTimerHandlerI();
-  chSysIRQExitI();
+  chSysUnlockI();
+
+  SYS_IRQ_EPILOGUE();
 }
diff --git a/ports/MSP430/chcore.c b/ports/MSP430/chcore.c
index e9a5dc574..e56f41120 100644
--- a/ports/MSP430/chcore.c
+++ b/ports/MSP430/chcore.c
@@ -31,12 +31,55 @@
  * because performance concerns.
  */
 
+/**
+ * The default implementation of this function is void so no messages are
+ * actually printed.
+ * @note The function is declared as a weak symbol, it is possible to redefine
+ *       it in your application code.
+ * @param msg pointer to the message string
+ */
+__attribute__((weak))
 void sys_puts(char *msg) {
 }
 
+/**
+ * Performs a context switch between two threads.
+ * @param otp the thread to be switched out
+ * @param ntp the thread to be switched in
+ * @note The function is declared as a weak symbol, it is possible to redefine
+ *       it in your application code.
+ */
+__attribute__((naked, weak))
 void sys_switch(Thread *otp, Thread *ntp) {
+  register struct intctx *sp asm("r1");
+
+  asm volatile ("push    r11                                    \n\t" \
+                "push    r10                                    \n\t" \
+                "push    r9                                     \n\t" \
+                "push    r8                                     \n\t" \
+                "push    r7                                     \n\t" \
+                "push    r6                                     \n\t" \
+                "push    r6                                     \n\t" \
+                "push    r4");
+  otp->p_ctx.sp = sp;
+  sp = ntp->p_ctx.sp;
+  asm volatile ("pop     r4                                     \n\t" \
+                "pop     r5                                     \n\t" \
+                "pop     r6                                     \n\t" \
+                "pop     r7                                     \n\t" \
+                "pop     r8                                     \n\t" \
+                "pop     r9                                     \n\t" \
+                "pop     r10                                    \n\t" \
+                "pop     r11                                    \n\t" \
+                "ret" : : "r" (sp));
 }
 
+/**
+ * Disables the interrupts and halts the system.
+ * @note The function is declared as a weak symbol, it is possible to redefine
+ *       it in your application code.
+ */
+__attribute__((weak))
 void sys_halt(void) {
 
   sys_disable();
@@ -44,4 +87,16 @@ void sys_halt(void) {
   }
 }
 
+/**
+ * Start a thread by invoking its work function.
+ * If the work function returns @p chThdExit() is automatically invoked.
+ */
+void threadstart(void) {
+
+  asm volatile ("eint                                           \n\t" \
+                "mov     r11, r15                               \n\t" \
+                "call    r10                                    \n\t" \
+                "call    #chThdExit");
+}
+
 /** @} */
diff --git a/ports/MSP430/chcore.h b/ports/MSP430/chcore.h
index db0d25f77..a4a866f11 100644
--- a/ports/MSP430/chcore.h
+++ b/ports/MSP430/chcore.h
@@ -150,6 +150,12 @@ if (chSchRescRequiredI())                                               \
   chSchDoRescheduleI();                                                 \
 }
 
+/**
+ * IRQ handler function modifier. Note it just aliases the WinMSP "interrupt"
+ * macro.
+ */
+#define SYS_IRQ_HANDLER interrupt
+
 /**
  * This port function is implemented as inlined code for performance reasons.
  */
@@ -181,11 +187,6 @@ if (chSchRescRequiredI())                                               \
 #define sys_wait_for_interrupt()
 #endif
 
-/**
- * IRQ handler function modifier.
- */
-#define SYS_IRQ_HANDLER
-
 #ifdef __cplusplus
 extern "C" {
 #endif
diff --git a/ports/MSP430/msp430_serial.c b/ports/MSP430/msp430_serial.c
index 384cda0fc..27094edeb 100644
--- a/ports/MSP430/msp430_serial.c
+++ b/ports/MSP430/msp430_serial.c
@@ -34,7 +34,9 @@ static void SetError(uint8_t urctl, FullDuplexDriver *com) {
     sts |= SD_FRAMING_ERROR;
   if (urctl & BRK)
     sts |= SD_BREAK_DETECTED;
+  chSysLockI();
   chFDDAddFlagsI(com, sts);
+  chSysUnlockI();
 }
 
 #ifdef USE_MSP430_USART0
@@ -42,30 +44,34 @@ FullDuplexDriver COM1;
 static uint8_t ib1[SERIAL_BUFFERS_SIZE];
 static uint8_t ob1[SERIAL_BUFFERS_SIZE];
 
-interrupt(USART0TX_VECTOR) u0txirq(void) {
+SYS_IRQ_HANDLER(USART0TX_VECTOR) u0txirq(void) {
   msg_t b;
 
-  chSysIRQEnterI();
+  SYS_IRQ_PROLOGUE();
 
+  chSysLockI();
   b = chFDDRequestDataI(&COM1);
+  chSysUnlockI();
   if (b < Q_OK)
     U0IE &= ~UTXIE0;
   else
     U0TXBUF = b;
 
-  chSysIRQExitI();
+  SYS_IRQ_EPILOGUE();
 }
 
-interrupt(USART0RX_VECTOR) u0rxirq(void) {
+SYS_IRQ_HANDLER(USART0RX_VECTOR) u0rxirq(void) {
   uint8_t urctl;
 
-  chSysIRQEnterI();
+  SYS_IRQ_PROLOGUE();
 
   if ((urctl = U0RCTL) & RXERR)
     SetError(urctl, &COM1);
+  chSysLockI();
   chFDDIncomingDataI(&COM1, U0RXBUF);
+  chSysUnlockI();
 
-  chSysIRQExitI();
+  SYS_IRQ_EPILOGUE();
 }
 
 /*
@@ -75,7 +81,9 @@ interrupt(USART0RX_VECTOR) u0rxirq(void) {
 static void OutNotify1(void) {
 
   if (!(U0IE & UTXIE0)) {
+    chSysLockI();
     U0TXBUF = (uint8_t)chFDDRequestDataI(&COM1);
+    chSysUnlockI();
     U0IE |= UTXIE0;
   }
 }
@@ -108,30 +116,34 @@ FullDuplexDriver COM2;
 static uint8_t ib2[SERIAL_BUFFERS_SIZE];
 static uint8_t ob2[SERIAL_BUFFERS_SIZE];
 
-interrupt(USART1TX_VECTOR) u1txirq(void) {
+SYS_IRQ_HANDLER(USART1TX_VECTOR) u1txirq(void) {
   msg_t b;
 
-  chSysIRQEnterI();
+  SYS_IRQ_PROLOGUE();
 
+  chSysLockI();
   b = chFDDRequestDataI(&COM2);
+  chSysUnlockI();
   if (b < Q_OK)
     U1IE &= ~UTXIE1;
   else
     U1TXBUF = b;
 
-  chSysIRQExitI();
+  SYS_IRQ_EPILOGUE();
 }
 
-interrupt(USART1RX_VECTOR) u1rxirq(void) {
+SYS_IRQ_HANDLER(USART1RX_VECTOR) u1rxirq(void) {
   uint8_t urctl;
 
-  chSysIRQEnterI();
+  SYS_IRQ_PROLOGUE();
 
   if ((urctl = U1RCTL) & RXERR)
     SetError(urctl, &COM2);
+  chSysLockI();
   chFDDIncomingDataI(&COM2, U1RXBUF);
+  chSysUnlockI();
 
-  chSysIRQExitI();
+  SYS_IRQ_EPILOGUE();
 }