diff --git a/build/libraries/fs/ARM7/src/fs_loader.c b/build/libraries/fs/ARM7/src/fs_loader.c
index 3ba74a87..803384c3 100644
--- a/build/libraries/fs/ARM7/src/fs_loader.c
+++ b/build/libraries/fs/ARM7/src/fs_loader.c
@@ -124,8 +124,10 @@ BOOL FS_LoadBuffer( int fd, u32 offset, u32 size )
         u8* dest = aesFlag ? aesBuffer :
                     (u8*)HW_FIRM_LOAD_BUFFER_BASE + count * HW_FIRM_LOAD_BUFFER_UNIT_SIZE;
         u32 unit = size < HW_FIRM_LOAD_BUFFER_UNIT_SIZE ? size : HW_FIRM_LOAD_BUFFER_UNIT_SIZE;
-        while ( MI_GetWramBankMaster_B( count ) != MI_WRAM_ARM7 ) // wait to be ready
+        PXI_AcquireLoadBufferSemaphore(); // wait to be ready
+        if ( MI_GetWramBankMaster_B( count ) != MI_WRAM_ARM7 )
         {
+            OS_TPanic("PROGRAM ERROR!");
         }
 #ifdef WORKAROUND_NAND_2KB_BUG
         {
@@ -152,7 +154,7 @@ BOOL FS_LoadBuffer( int fd, u32 offset, u32 size )
         {
             CopyWithAes( dest, (u8*)HW_FIRM_LOAD_BUFFER_BASE + count * HW_FIRM_LOAD_BUFFER_UNIT_SIZE, unit );
         }
-        PXI_NotifyID( FIRM_PXI_ID_LOAD_PIRIOD );
+        PXI_ReleaseLoadBufferSemaphore();
         count = ( count + 1 ) % HW_FIRM_LOAD_BUFFER_UNIT_NUMS;
         size -= unit;
     }
diff --git a/build/libraries/fs/ARM9/src/fs_loader.c b/build/libraries/fs/ARM9/src/fs_loader.c
index 335e8311..f5d623bc 100644
--- a/build/libraries/fs/ARM9/src/fs_loader.c
+++ b/build/libraries/fs/ARM9/src/fs_loader.c
@@ -179,10 +179,7 @@ BOOL FS_LoadBuffer( u8* dest, u32 size, SVCSHA1Context *ctx )
     {
         u8* src = (u8*)HW_FIRM_LOAD_BUFFER_BASE + count * HW_FIRM_LOAD_BUFFER_UNIT_SIZE;
         u32 unit = size < HW_FIRM_LOAD_BUFFER_UNIT_SIZE ? size : HW_FIRM_LOAD_BUFFER_UNIT_SIZE;
-        if ( PXI_RecvID() != FIRM_PXI_ID_LOAD_PIRIOD )
-        {
-            return FALSE;
-        }
+        PXI_AcquireLoadBufferSemaphore(); // wait to be ready
         MIi_SetWramBankMaster_B( count, MI_WRAM_ARM9 );
         if (ctx)
         {
@@ -204,6 +201,7 @@ BOOL FS_LoadBuffer( u8* dest, u32 size, SVCSHA1Context *ctx )
         size -= unit;
         dest += unit;
         MIi_SetWramBankMaster_B( count, MI_WRAM_ARM7 );
+        PXI_ReleaseLoadBufferSemaphore();
         count = ( count + 1 ) % HW_FIRM_LOAD_BUFFER_UNIT_NUMS;
     }
     return TRUE;
diff --git a/build/libraries/pxi/common/pxi_firm.c b/build/libraries/pxi/common/pxi_firm.c
index 74f51a65..c7913ee1 100644
--- a/build/libraries/pxi/common/pxi_firm.c
+++ b/build/libraries/pxi/common/pxi_firm.c
@@ -24,8 +24,11 @@ typedef struct
 {
     u32 wp;
     u32 rp;
+
     u8 id[PXI_FIRM_ID_MAX];
 
+    u32 semaphore;  // for fs_loader.c
+
     u32 length;
     u32 current;
     u8 data[PXI_FIRM_STREAM_MAX];
@@ -66,6 +69,18 @@ static void PxiFirmIDCallback( PXIFifoTag tag, u32 data, BOOL err )
     u32 next_wp = ( work.wp + 1 ) % PXI_FIRM_ID_MAX;
     (void)tag;
     (void)err;
+
+    // special ID
+    if ( data == FIRM_PXI_ID_LOAD_BUFFER_SEMAPHORE )
+    {
+        work.semaphore++;
+        if ( work.semaphore > HW_FIRM_LOAD_BUFFER_UNIT_NUMS )
+        {
+            OS_TPanic("PROGRAM ERROR: Semaphore counter was overlow.");
+        }
+        return;
+    }
+
     if ( next_wp != work.rp )
     {
         work.wp = next_wp;
@@ -93,6 +108,7 @@ void PXI_InitFIRM(void)
     while (!PXI_IsCallbackReady(PXI_FIFO_TAG_USER_0, PXI_PROC_ARM7))
     {
     }
+    work.semaphore = 0;
 #endif
     work.rp = work.wp = work.length = 0;
     PXI_SetFifoRecvCallback( PXI_FIFO_TAG_USER_0, PxiFirmStreamCallback );
@@ -101,6 +117,7 @@ void PXI_InitFIRM(void)
     while (!PXI_IsCallbackReady(PXI_FIFO_TAG_USER_1, PXI_PROC_ARM9))
     {
     }
+    work.semaphore = HW_FIRM_LOAD_BUFFER_UNIT_NUMS;
 #endif
 }
 
@@ -220,6 +237,44 @@ FIRMPxiID PXI_RecvID( void )
     }
 }
 
+/*---------------------------------------------------------------------------*
+  Name:         PXI_ReleaseLoadBufferSemaphore
+
+  Description:  Release semaphore for *_LoadBuffer
+
+  Arguments:    None.
+
+  Returns:      None.
+ *---------------------------------------------------------------------------*/
+void PXI_ReleaseLoadBufferSemaphore( void )
+{
+    PXI_NotifyID( FIRM_PXI_ID_LOAD_BUFFER_SEMAPHORE );
+}
+
+/*---------------------------------------------------------------------------*
+  Name:         PXI_AcquireLoadBufferSemaphore
+
+  Description:  Acquire semaphore for *_LoadBuffer
+
+  Arguments:    None.
+
+  Returns:      None.
+ *---------------------------------------------------------------------------*/
+void PXI_AcquireLoadBufferSemaphore( void )
+{
+    while ( 1 )
+    {
+        OSIntrMode enabled = OS_DisableInterrupts();
+        if ( work.semaphore > 0 )
+        {
+            work.semaphore--;
+            OS_RestoreInterrupts( enabled );
+            return;
+        }
+        OS_RestoreInterrupts( enabled );
+    }
+}
+
 /*---------------------------------------------------------------------------*
   Name:         PXIi_SendIDByIntf
 
diff --git a/include/firm/pxi/common/pxi_firm.h b/include/firm/pxi/common/pxi_firm.h
index b6eb7687..2abcda25 100644
--- a/include/firm/pxi/common/pxi_firm.h
+++ b/include/firm/pxi/common/pxi_firm.h
@@ -36,7 +36,7 @@ typedef enum
     FIRM_PXI_ID_LOAD_HEADER = 6,    // FATFS_LoadHeader
     FIRM_PXI_ID_LOAD_STATIC = 5,    // FATFS_LoadStatic
 
-    FIRM_PXI_ID_LOAD_PIRIOD = 1,    // *_LoadBuffer
+    FIRM_PXI_ID_LOAD_BUFFER_SEMAPHORE = 1,    // *_LoadBuffer
 
     // from ARM9
     FIRM_PXI_ID_INIT_MMEM = 3,  // _start
@@ -114,6 +114,28 @@ void PXI_NotifyID( FIRMPxiID id );
  *---------------------------------------------------------------------------*/
 FIRMPxiID PXI_RecvID( void );
 
+/*---------------------------------------------------------------------------*
+  Name:         PXI_ReleaseLoadBufferSemaphore
+
+  Description:  Release semaphore for *_LoadBuffer
+
+  Arguments:    None.
+
+  Returns:      None.
+ *---------------------------------------------------------------------------*/
+void PXI_ReleaseLoadBufferSemaphore( void );
+
+/*---------------------------------------------------------------------------*
+  Name:         PXI_AcquireLoadBufferSemaphore
+
+  Description:  Acquire semaphore for *_LoadBuffer
+
+  Arguments:    None.
+
+  Returns:      None.
+ *---------------------------------------------------------------------------*/
+void PXI_AcquireLoadBufferSemaphore( void );
+
 /*---------------------------------------------------------------------------*
   Name:         PXIi_SendIDByIntf