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diff --git a/PerformancePkg/Library/TscTimerLib/TscTimerLibInternal.h b/PerformancePkg/Library/TscTimerLib/TscTimerLibInternal.h
new file mode 100644
index 000000000..a4ed0ebb3
--- /dev/null
+++ b/PerformancePkg/Library/TscTimerLib/TscTimerLibInternal.h
@@ -0,0 +1,55 @@
+/** @file
+  Internal header file for TscTimerLib instances.
+
+  Copyright (c) 2009 - 2011, Intel Corporation. All rights reserved.<BR>
+  This program and the accompanying materials
+  are licensed and made available under the terms and conditions of the BSD License
+  which accompanies this distribution. The full text of the license may be found at
+  http://opensource.org/licenses/bsd-license.php
+
+  THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
+  WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
+
+**/
+
+#ifndef _TSC_TIMER_LIB_INTERNAL_H_
+#define _TSC_TIMER_LIB_INTERNAL_H_
+
+#include <Ich/GenericIch.h>
+
+#include <Library/TimerLib.h>
+#include <Library/BaseLib.h>
+#include <Library/IoLib.h>
+#include <Library/PciLib.h>
+#include <Library/PcdLib.h>
+
+/**  Get TSC frequency.
+
+  @return The number of TSC counts per second.
+
+**/
+UINT64
+InternalGetTscFrequency (
+  VOID
+  );
+
+/**  Calculate TSC frequency.
+
+  The TSC counting frequency is determined by comparing how far it counts
+  during a 1ms period as determined by the ACPI timer. The ACPI timer is
+  used because it counts at a known frequency.
+  If ACPI I/O space not enabled, this function will enable it. Then the
+  TSC is sampled, followed by waiting for 3579 clocks of the ACPI timer, or 1ms.
+  The TSC is then sampled again. The difference multiplied by 1000 is the TSC
+  frequency. There will be a small error because of the overhead of reading
+  the ACPI timer. An attempt is made to determine and compensate for this error.
+
+  @return The number of TSC counts per second.
+
+**/
+UINT64
+InternalCalculateTscFrequency (
+  VOID
+  );
+
+#endif