diff --git a/build/libraries/os/ARM9/Makefile b/build/libraries/os/ARM9/Makefile
index 4f840f5..a8f7940 100644
--- a/build/libraries/os/ARM9/Makefile
+++ b/build/libraries/os/ARM9/Makefile
@@ -52,6 +52,7 @@ SRCS			= \
 			  os_message.c		\
 			  os_mutex.c		\
 			  os_cache.c		\
+			  os_cache_tag.c	\
 			  os_arena.c		\
 			  os_alloc.c		\
 			  os_tcm.c		\
diff --git a/build/libraries/os/ARM9/os_cache_tag.c b/build/libraries/os/ARM9/os_cache_tag.c
new file mode 100644
index 0000000..8c39ed1
--- /dev/null
+++ b/build/libraries/os/ARM9/os_cache_tag.c
@@ -0,0 +1,268 @@
+/*---------------------------------------------------------------------------*
+  Project:  TwlFirm - OS
+  File:     os_cache_tag.c
+
+  Copyright 2007 Nintendo.  All rights reserved.
+
+  These coded instructions, statements, and computer programs contain
+  proprietary information of Nintendo of America Inc. and/or Nintendo
+  Company Ltd., and are protected by Federal copyright law.  They may
+  not be disclosed to third parties or copied or duplicated in any form,
+  in whole or in part, without the prior written consent of Nintendo.
+
+  $Log: $
+  $NoKeywords: $
+ *---------------------------------------------------------------------------*/
+#include <twl/os.h>
+#include <nitro/code32.h>
+
+
+//===========================================================================
+//              DATA CACHE (for specified range)
+//===========================================================================
+/*---------------------------------------------------------------------------*
+  Name:         DC_ClearTagAll
+
+  Description:  clear tag in data cache
+
+  Arguments:    None
+
+  Returns:      None.
+ *---------------------------------------------------------------------------*/
+void DC_ClearTagAll( void )
+{
+    DC_FillTagAll( 0 );
+}
+
+/*---------------------------------------------------------------------------*
+  Name:         DC_FillTagAll
+
+  Description:  clear tag in data cache
+
+  Arguments:    data :  fill data
+
+  Returns:      None.
+ *---------------------------------------------------------------------------*/
+asm void DC_FillTagAll( u32 data )
+{
+    mov         r12, #0
+@1:
+    mov         r2, #0
+@2:
+    orr         r3, r2, r12
+    mcr         p15, 3, r3, c15, c0, 0  // set index
+    mcr         p15, 3, r0, c15, c2, 0  // clear tag
+    add         r2, r2, #HW_CACHE_LINE_SIZE
+    cmp         r2, #HW_DCACHE_SIZE/4
+    blt         @2
+
+    add         r12, r12, #1<<HW_C7_CACHE_SET_NO_SHIFT
+    cmp         r12, #0
+    bne         @1
+
+    bx          lr
+}
+
+/*---------------------------------------------------------------------------*
+  Name:         DC_ClearDataAll
+
+  Description:  clear data in data cache
+
+  Arguments:    None
+
+  Returns:      None.
+ *---------------------------------------------------------------------------*/
+void DC_ClearDataAll( void )
+{
+    DC_FillDataAll( 0 );
+}
+
+/*---------------------------------------------------------------------------*
+  Name:         DC_FillDataAll
+
+  Description:  fill data in data cache
+
+  Arguments:    data :  fill data
+
+  Returns:      None.
+ *---------------------------------------------------------------------------*/
+asm void DC_FillDataAll( u32 data )
+{
+    mov         r12, #0
+@1:
+    mov         r2, #0
+@2:
+    orr         r3, r2, r12
+    mcr         p15, 3, r3, c15, c0, 0  // set index
+    mcr         p15, 3, r0, c15, c4, 0  // clear data
+    add         r2, r2, #4
+    cmp         r2, #HW_DCACHE_SIZE/4
+    blt         @2
+
+    add         r12, r12, #1<<HW_C7_CACHE_SET_NO_SHIFT
+    cmp         r12, #0
+    bne         @1
+
+    bx          lr
+}
+
+/*---------------------------------------------------------------------------*
+  Name:         DC_GetTagAndDataAll
+
+  Description:  get tag and data in data cache
+
+  Arguments:    tag           tag address
+                data          data address
+
+  Returns:      None.
+ *---------------------------------------------------------------------------*/
+asm void DC_GetTagAndDataAll( void* tag, void* data )
+{
+    mov         r12, #0
+@1:
+    mov         r2, #0
+@2:
+    orr         r3, r2, r12
+    mcr         p15, 3, r3, c15, c0, 0  // set index
+    tst         r2, #HW_CACHE_LINE_SIZE - 1
+    mrceq       p15, 3, r3, c15, c2, 0  // get tag
+    streq       r3, [r0], #4
+    mrc         p15, 3, r3, c15, c4, 0  // get data
+    str         r3, [r1], #4
+    add         r2, r2, #4
+    cmp         r2, #HW_DCACHE_SIZE/4
+    blt         @2
+
+    add         r12, r12, #1<<HW_C7_CACHE_SET_NO_SHIFT
+    cmp         r12, #0
+    bne         @1
+
+    bx          lr
+}
+
+
+//===========================================================================
+//              INSTRUCTION CACHE
+//===========================================================================
+/*---------------------------------------------------------------------------*
+  Name:         IC_ClearTagAll
+
+  Description:  clear tag in instruction cache
+
+  Arguments:    None
+
+  Returns:      None.
+ *---------------------------------------------------------------------------*/
+void IC_ClearTagAll( void )
+{
+    IC_FillTagAll( 0 );
+}
+
+/*---------------------------------------------------------------------------*
+  Name:         IC_FillTagAll
+
+  Description:  fill tag in instruction cache
+
+  Arguments:    None
+
+  Returns:      None.
+ *---------------------------------------------------------------------------*/
+asm void IC_FillTagAll( u32 data )
+{
+    mov         r12, #0
+@1:
+    mov         r2, #0
+@2:
+    orr         r3, r2, r12
+    mcr         p15, 3, r3, c15, c0, 0  // set index
+    mcr         p15, 3, r0, c15, c1, 0  // clear tag
+    add         r2, r2, #HW_CACHE_LINE_SIZE
+    cmp         r2, #HW_ICACHE_SIZE/4
+    blt         @2
+
+    add         r12, r12, #1<<HW_C7_CACHE_SET_NO_SHIFT
+    cmp         r12, #0
+    bne         @1
+
+    bx          lr
+}
+
+/*---------------------------------------------------------------------------*
+  Name:         IC_ClearInstructionAll
+
+  Description:  clear instruction in instruction cache
+
+  Arguments:    None
+
+  Returns:      None.
+ *---------------------------------------------------------------------------*/
+void IC_ClearInstructionAll( void )
+{
+    IC_FillInstructionAll( 0 );
+}
+
+/*---------------------------------------------------------------------------*
+  Name:         IC_FillInstructionAll
+
+  Description:  fill instruction in instruction cache
+
+  Arguments:    data :  fill data
+
+  Returns:      None.
+ *---------------------------------------------------------------------------*/
+asm void IC_FillInstructionAll( u32 data )
+{
+    mov         r12, #0
+@1:
+    mov         r2, #0
+@2:
+    orr         r3, r2, r12
+    mcr         p15, 3, r3, c15, c0, 0  // set index
+    mcr         p15, 3, r0, c15, c3, 0  // clear data
+    add         r2, r2, #4
+    cmp         r2, #HW_ICACHE_SIZE/4
+    blt         @2
+
+    add         r12, r12, #1<<HW_C7_CACHE_SET_NO_SHIFT
+    cmp         r12, #0
+    bne         @1
+
+    bx          lr
+}
+
+/*---------------------------------------------------------------------------*
+  Name:         IC_GetTagAndInstructionAll
+
+  Description:  get tag and instruction in instruction cache
+
+  Arguments:    tag           tag address
+                inst          instruction address
+
+  Returns:      None.
+ *---------------------------------------------------------------------------*/
+asm void IC_GetTagAndInstructionAll( void* tag, void* inst )
+{
+    mov         r12, #0
+@1:
+    mov         r2, #0
+@2:
+    orr         r3, r2, r12
+    mcr         p15, 3, r3, c15, c0, 0  // set index
+    tst         r2, #HW_CACHE_LINE_SIZE - 1
+    mrceq       p15, 3, r3, c15, c1, 0  // get tag
+    streq       r3, [r0], #4
+    mrc         p15, 3, r3, c15, c3, 0  // get data
+    str         r3, [r1], #4
+    add         r2, r2, #4
+    cmp         r2, #HW_ICACHE_SIZE/4
+    blt         @2
+
+    add         r12, r12, #1<<HW_C7_CACHE_SET_NO_SHIFT
+    cmp         r12, #0
+    bne         @1
+
+    bx          lr
+}
+
+
+#include <nitro/codereset.h>
diff --git a/include/twl/os.h b/include/twl/os.h
index bebef23..7f341d3 100644
--- a/include/twl/os.h
+++ b/include/twl/os.h
@@ -23,6 +23,10 @@
 #include <twl/os/common/emulator.h>
 #include <twl/os/common/systemCall.h>
 
+#ifdef SDK_ARM9
+#include <twl/os/ARM9/cache_tag.h>
+#endif // SDK_ARM9
+
 #ifdef SDK_DEBUGGER_KMC
 #include <twl/vlink.h>
 #endif // SDK_DEBUGGER_KMC
diff --git a/include/twl/os/ARM9/cache_tag.h b/include/twl/os/ARM9/cache_tag.h
new file mode 100644
index 0000000..31c65e7
--- /dev/null
+++ b/include/twl/os/ARM9/cache_tag.h
@@ -0,0 +1,150 @@
+/*---------------------------------------------------------------------------*
+  Project:  TwlFirm - OS - include 
+  File:     cache_tag.h
+
+  Copyright 2007 Nintendo.  All rights reserved.
+
+  These coded instructions, statements, and computer programs contain
+  proprietary information of Nintendo of America Inc. and/or Nintendo
+  Company Ltd., and are protected by Federal copyright law.  They may
+  not be disclosed to third parties or copied or duplicated in any form,
+  in whole or in part, without the prior written consent of Nintendo.
+
+  $Log: $
+  $NoKeywords: $
+ *---------------------------------------------------------------------------*/
+
+#ifndef TWL_OS_CACHE_TAG_H_
+#define TWL_OS_CACHE_TAG_H_
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include <twl/misc.h>
+#include <twl/types.h>
+
+//===========================================================================
+//              DATA CACHE (for specified range)
+//===========================================================================
+/*---------------------------------------------------------------------------*
+  Name:         DC_ClearTagAll
+
+  Description:  clear tag in data cache
+
+  Arguments:    None
+
+  Returns:      None.
+ *---------------------------------------------------------------------------*/
+void    DC_ClearTagAll( void );
+
+/*---------------------------------------------------------------------------*
+  Name:         DC_ClearDataAll
+
+  Description:  clear data in data cache
+
+  Arguments:    None
+
+  Returns:      None.
+ *---------------------------------------------------------------------------*/
+void    DC_ClearDataAll( void );
+
+/*---------------------------------------------------------------------------*
+  Name:         DC_FillTagAll
+
+  Description:  clear tag in data cache
+
+  Arguments:    data :  fill data
+
+  Returns:      None.
+ *---------------------------------------------------------------------------*/
+void    DC_FillTagAll( u32 data );
+
+/*---------------------------------------------------------------------------*
+  Name:         DC_FillDataAll
+
+  Description:  fill data in data cache
+
+  Arguments:    data :  fill data
+
+  Returns:      None.
+ *---------------------------------------------------------------------------*/
+void    DC_FillDataAll( u32 data );
+
+/*---------------------------------------------------------------------------*
+  Name:         DC_GetTagAndDataAll
+
+  Description:  get tag and data in data cache
+
+  Arguments:    tag           tag address
+                data          data address
+
+  Returns:      None.
+ *---------------------------------------------------------------------------*/
+void    DC_GetTagAndDataAll( void* tag, void* data );
+
+//===========================================================================
+//              INSTRUCTION CACHE
+//===========================================================================
+/*---------------------------------------------------------------------------*
+  Name:         IC_ClearTagAll
+
+  Description:  clear tag in instruction cache
+
+  Arguments:    None
+
+  Returns:      None.
+ *---------------------------------------------------------------------------*/
+void    IC_ClearTagAll( void );
+
+/*---------------------------------------------------------------------------*
+  Name:         IC_ClearInstructionAll
+
+  Description:  clear instruction in instruction cache
+
+  Arguments:    None
+
+  Returns:      None.
+ *---------------------------------------------------------------------------*/
+void    IC_ClearInstructionAll( void );
+
+/*---------------------------------------------------------------------------*
+  Name:         IC_FillTagAll
+
+  Description:  fill tag in instruction cache
+
+  Arguments:    None
+
+  Returns:      None.
+ *---------------------------------------------------------------------------*/
+void    IC_FillTagAll( u32 data );
+
+/*---------------------------------------------------------------------------*
+  Name:         IC_FillInstructionAll
+
+  Description:  fill instruction in instruction cache
+
+  Arguments:    data :  fill data
+
+  Returns:      None.
+ *---------------------------------------------------------------------------*/
+void    IC_FillInstructionAll( u32 data );
+
+/*---------------------------------------------------------------------------*
+  Name:         IC_GetTagAndInstructionAll
+
+  Description:  get tag and instruction in instruction cache
+
+  Arguments:    tag           tag address
+                inst          instruction address
+
+  Returns:      None.
+ *---------------------------------------------------------------------------*/
+void    IC_GetTagAndInstructionAll( void* tag, void* inst );
+
+#ifdef __cplusplus
+} /* extern "C" */
+#endif
+
+/* TWL_OS_CACHE_TAG_H_ */
+#endif