diff --git a/src/libCom/Makefile b/src/libCom/Makefile
index 3d251f35c..01e517080 100644
--- a/src/libCom/Makefile
+++ b/src/libCom/Makefile
@@ -192,6 +192,7 @@ INC += epicsStdioRedirect.h
 INC += epicsGetopt.h
 
 INC += devLib.h
+INC += devLibImpl.h
 INC += osdVME.h
 
 SRCS += epicsThread.cpp
diff --git a/src/libCom/osi/devLib.c b/src/libCom/osi/devLib.c
index 6a8aa68e6..f56c63968 100644
--- a/src/libCom/osi/devLib.c
+++ b/src/libCom/osi/devLib.c
@@ -29,7 +29,10 @@ static const char sccsID[] = "@(#) $Id$";
 #include "epicsMutex.h"
 #include "errlog.h"
 #include "ellLib.h"
+
+#define NO_DEVLIB_COMPAT
 #include "devLib.h"
+#include "devLibImpl.h"
 
 static ELLLIST addrAlloc[atLast];
 static ELLLIST addrFree[atLast];
diff --git a/src/libCom/osi/devLib.h b/src/libCom/osi/devLib.h
index 2cd2471e8..d0f444fc3 100644
--- a/src/libCom/osi/devLib.h
+++ b/src/libCom/osi/devLib.h
@@ -46,6 +46,21 @@ typedef enum {
  */
 extern const char *epicsAddressTypeName[];
 
+#ifdef __cplusplus
+}
+#endif
+
+/*
+ * To retain compatibility include everything by default
+ */
+#ifndef NO_DEVLIB_COMPAT
+#  include  "devLibImpl.h"
+#endif
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 epicsShareFunc long devAddressMap(void); /* print an address map */
 
 /*
@@ -280,64 +295,6 @@ epicsShareFunc void devLibA24Free(void *pBlock);
  */
 #define devPtrAlignTest(PTR) (!(devCreateAlignmentMask(*PTR)&(long)(PTR)))
 
-/*
- * virtual OS layer for devLib.c
- */
-typedef struct devLibVirtualOS {
-	/*
-	 * maps logical address to physical address, but does not detect
-	 * two device drivers that are using the same address range
-	 */
-	long (*pDevMapAddr) (epicsAddressType addrType, unsigned options,
-			size_t logicalAddress, size_t size, volatile void **ppPhysicalAddress);
-
-	/*
-	 * a bus error safe "wordSize" read at the specified address which returns 
-	 * unsuccessful status if the device isnt present
-	 */
-	long (*pDevReadProbe) (unsigned wordSize, volatile const void *ptr, void *pValueRead);
-
-	/*
-	 * a bus error safe "wordSize" write at the specified address which returns 
-	 * unsuccessful status if the device isnt present
-	 */
-	long (*pDevWriteProbe) (unsigned wordSize, volatile void *ptr, const void *pValueWritten);
-
-	/*
-	 * connect ISR to a VME interrupt vector
-	 * (required for backwards compatibility)
-	 */
-	long (*pDevConnectInterruptVME) (unsigned vectorNumber, 
-						void (*pFunction)(void *), void  *parameter);
-
-	/*
-	 * disconnect ISR from a VME interrupt vector
-	 * (required for backwards compatibility)
-	 */
-	long (*pDevDisconnectInterruptVME) (unsigned vectorNumber,
-						void (*pFunction)(void *));
-
-	/*
-	 * enable VME interrupt level
-	 */
-	long (*pDevEnableInterruptLevelVME) (unsigned level);
-
-	/*
-	 * disable VME interrupt level
-	 */
-	long (*pDevDisableInterruptLevelVME) (unsigned level);
-        /* malloc/free A24 address space */
-        void *(*pDevA24Malloc)(size_t nbytes);
-        void (*pDevA24Free)(void *pBlock);
-        long (*pDevInit)(void);
-
-	/*
-	 * test if VME interrupt has an ISR connected
-	 */
-	int (*pDevInterruptInUseVME) (unsigned vectorNumber);
-}devLibVirtualOS;
-epicsShareExtern devLibVirtualOS *pdevLibVirtualOS;
-
 /*
  * error codes (and messages) associated with devLib.c
  */
diff --git a/src/libCom/osi/devLibVMEImpl.h b/src/libCom/osi/devLibVMEImpl.h
new file mode 100644
index 000000000..775bc3b42
--- /dev/null
+++ b/src/libCom/osi/devLibVMEImpl.h
@@ -0,0 +1,97 @@
+/*************************************************************************\
+* Copyright (c) 2008 UChicago Argonne LLC, as Operator of Argonne
+*     National Laboratory.
+* Copyright (c) 2002 The Regents of the University of California, as
+*     Operator of Los Alamos National Laboratory.
+* EPICS BASE is distributed subject to a Software License Agreement found
+* in file LICENSE that is included with this distribution. 
+\*************************************************************************/
+/* devLibImpl.h */
+/*  */
+
+/*
+ * Original Author: Marty Kraimer 
+ *  Author:     Jeff Hill
+ *  Date:       03-10-93
+ */
+
+#ifndef INCdevLibImplh
+#define INCdevLibImplh 1
+
+#include "dbDefs.h"
+#include "shareLib.h"
+#include "devLib.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/*
+ * virtual OS layer for devLib.c
+ *
+ * The global virtual OS table pdevLibVirtualOS controls
+ * the behaviour of the functions defined in devLib.h.
+ * All of which call into the functions found in this table
+ * to perform system specific tasks.
+ */
+typedef struct devLibVirtualOS {
+	/*
+	 * maps logical address to physical address, but does not detect
+	 * two device drivers that are using the same address range
+	 */
+	long (*pDevMapAddr) (epicsAddressType addrType, unsigned options,
+			size_t logicalAddress, size_t size, volatile void **ppPhysicalAddress);
+
+	/*
+	 * a bus error safe "wordSize" read at the specified address which returns 
+	 * unsuccessful status if the device isnt present
+	 */
+	long (*pDevReadProbe) (unsigned wordSize, volatile const void *ptr, void *pValueRead);
+
+	/*
+	 * a bus error safe "wordSize" write at the specified address which returns 
+	 * unsuccessful status if the device isnt present
+	 */
+	long (*pDevWriteProbe) (unsigned wordSize, volatile void *ptr, const void *pValueWritten);
+
+	/*
+	 * connect ISR to a VME interrupt vector
+	 * (required for backwards compatibility)
+	 */
+	long (*pDevConnectInterruptVME) (unsigned vectorNumber, 
+						void (*pFunction)(void *), void  *parameter);
+
+	/*
+	 * disconnect ISR from a VME interrupt vector
+	 * (required for backwards compatibility)
+	 */
+	long (*pDevDisconnectInterruptVME) (unsigned vectorNumber,
+						void (*pFunction)(void *));
+
+	/*
+	 * enable VME interrupt level
+	 */
+	long (*pDevEnableInterruptLevelVME) (unsigned level);
+
+	/*
+	 * disable VME interrupt level
+	 */
+	long (*pDevDisableInterruptLevelVME) (unsigned level);
+        /* malloc/free A24 address space */
+        void *(*pDevA24Malloc)(size_t nbytes);
+        void (*pDevA24Free)(void *pBlock);
+        long (*pDevInit)(void);
+
+	/*
+	 * test if VME interrupt has an ISR connected
+	 */
+	int (*pDevInterruptInUseVME) (unsigned vectorNumber);
+}devLibVirtualOS;
+
+epicsShareExtern devLibVirtualOS *pdevLibVirtualOS;
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* INCdevLibImplh */