diff --git a/history.txt b/history.txt
index 291c144..cb23fc6 100644
--- a/history.txt
+++ b/history.txt
@@ -1,6 +1,15 @@
 Genesis Plus for Gamecube
 ------------------------------
 
+
+1.3.1 (20/12/2008):
+-------------------
+[NGC/Wii]
+- improved sound engine
+- modified frame synchronization (now use audio DMA interrupt)
+
+
+
 1.3.0 (14/12/2008):
 -------------------
 [Genesis]
diff --git a/source/ngc/ngc.c b/source/ngc/ngc.c
index e7931e5..74f6b42 100644
--- a/source/ngc/ngc.c
+++ b/source/ngc/ngc.c
@@ -131,6 +131,7 @@ int main (int argc, char *argv[])
   DI_Init();
 #endif
 
+  long long now, prev;
   int RenderedFrameCount = 0;
   int FrameCount = 0;
 
@@ -189,27 +190,37 @@ int main (int argc, char *argv[])
   /* Emulation Loop */
   while (1)
   {
-    /* audio DMA starting point */
     ogc_audio__start();
-
-    if (frameticker > 1)
+    
+    if (gc_pal < 0)
     {
-        /* frameskipping */
-        frameticker--;
-        system_frame (1);
+      /* this code is NEVER executed */
+      /* strangely, when removing it, this makes the program crashing (why ?) */
+      prev = now = gettime();
+      while (diff_usec(prev, now) < 1) now = gettime();
+      prev = now;
     }
     else
     {
-      /* frame sync */
-      while (!frameticker) usleep(10);
+      if (frameticker > 1)
+      {
+        /* frameskipping */
+        frameticker--;
+        system_frame (1);
+      }
+      else
+      {
+        /* frame sync */
+        while (!frameticker) usleep(1);
 
-      /* frame rendering */
-      system_frame (0);
-      RenderedFrameCount++;
+        /* frame rendering */
+        system_frame (0);
+        RenderedFrameCount++;
+      }
+
+      frameticker--;
     }
 
-    frameticker--;
-
     /* update video & audio */
     ogc_audio__update();
     ogc_video__update();
@@ -237,6 +248,7 @@ int main (int argc, char *argv[])
       frameticker = 0;
       FrameCount = 0;
       RenderedFrameCount = 0;
+
     }
   }
   return 0;
diff --git a/source/ngc/ogc_audio.c b/source/ngc/ogc_audio.c
index 8491454..eb26987 100644
--- a/source/ngc/ogc_audio.c
+++ b/source/ngc/ogc_audio.c
@@ -33,7 +33,7 @@
 u8 soundbuffer[2][3840] ATTRIBUTE_ALIGN(32);
 
 /* Current work soundbuffer */
-u8 mixbuffer = 1;
+int mixbuffer;
 
 /* Current DMA status (1: DMA in progress, 0: DMA stopped) */ 
 static int IsPlaying  = 0;
@@ -102,9 +102,12 @@ void ogc_audio__start(void)
   if (!IsPlaying)
   {
     dma_len = vdp_pal ? 3840 : 3200;
+    memset(soundbuffer[0], 0, dma_len);
     AUDIO_InitDMA((u32) soundbuffer[0], dma_len);
+    DCFlushRange(soundbuffer[0], dma_len);
     AUDIO_StartDMA();
     IsPlaying = 1;
+    mixbuffer = 1;
   }
 }
 
@@ -119,6 +122,4 @@ void ogc_audio__stop(void)
 {
   AUDIO_StopDMA ();
   IsPlaying = 0;
-  mixbuffer = 1;
-  memset(soundbuffer, 0, 2 * 3840);
 }
diff --git a/source/ngc/ogc_audio.h b/source/ngc/ogc_audio.h
index 2c7575f..3dd8ad8 100644
--- a/source/ngc/ogc_audio.h
+++ b/source/ngc/ogc_audio.h
@@ -25,7 +25,7 @@
 #define _GC_AUDIO_H_
 
 extern u8 soundbuffer[2][3840];
-extern u8 mixbuffer;
+extern int mixbuffer;
 
 extern void ogc_audio__init(void);
 extern void ogc_audio__stop(void);
diff --git a/source/ngc/ogc_video.c b/source/ngc/ogc_video.c
index 43d725d..c39938e 100644
--- a/source/ngc/ogc_video.c
+++ b/source/ngc/ogc_video.c
@@ -35,7 +35,7 @@ sms_ntsc_setup_t sms_setup;
 sms_ntsc_t sms_ntsc;
 
 /*** PAL 50hz flag ***/
-BOOL gc_pal = 0;
+int gc_pal = 0;
 
 /*** VI ***/
 unsigned int *xfb[2];  /*** Double buffered            ***/
diff --git a/source/ngc/ogc_video.h b/source/ngc/ogc_video.h
index fd98674..b231286 100644
--- a/source/ngc/ogc_video.h
+++ b/source/ngc/ogc_video.h
@@ -28,7 +28,7 @@ extern void ogc_video__init(void);
 extern void ogc_video__update(void);
 extern void ogc_video__reset();
 
-extern BOOL gc_pal;
+extern int gc_pal;
 extern unsigned int *xfb[2];
 extern int whichfb;
 extern GXRModeObj *tvmodes[6];
diff --git a/source/sound/sound.c b/source/sound/sound.c
index 56cca23..fc3b474 100644
--- a/source/sound/sound.c
+++ b/source/sound/sound.c
@@ -61,7 +61,7 @@ static inline uint32 psg_sample_cnt(uint8 is_z80)
 /* update FM samples */
 static inline void fm_update()
 {
-  if(snd.fm.curStage - snd.fm.lastStage > 1)
+  if(snd.fm.curStage - snd.fm.lastStage > 0)
   {
     int *tempBuffer[2];
     
@@ -84,7 +84,7 @@ static inline void fm_update()
 /* update PSG samples */
 static inline void psg_update()
 {
-  if(snd.psg.curStage - snd.psg.lastStage > 1)
+  if(snd.psg.curStage - snd.psg.lastStage > 0)
   {
     int16 *tempBuffer = snd.psg.buffer + snd.psg.lastStage;
     SN76489_Update (0, tempBuffer, snd.psg.curStage - snd.psg.lastStage);
diff --git a/source/system.c b/source/system.c
index e6ee51e..bc22f86 100644
--- a/source/system.c
+++ b/source/system.c
@@ -170,7 +170,7 @@ int system_frame (int do_skip)
     {
 #ifdef NGC
       /* wait for RESET button to be released */
-      if (!SYS_ResetButtonDown())
+      while (SYS_ResetButtonDown());
 #endif
       gen_reset(0);
     }