diff --git a/VAX/vax630_defs.h b/VAX/vax630_defs.h
index b55d8ef8..90786157 100644
--- a/VAX/vax630_defs.h
+++ b/VAX/vax630_defs.h
@@ -340,8 +340,10 @@ typedef struct {
 #define INT_V_QVSS      21                              /* QVSS */
 #define INT_V_DMCRX     22
 #define INT_V_DMCTX     23
-#define INT_V_TDRX      24                              /* TU58 */
-#define INT_V_TDTX      25
+#define INT_V_DUPRX     24                              /* DPV11 */
+#define INT_V_DUPTX     25
+#define INT_V_TDRX      26                              /* TU58 */
+#define INT_V_TDTX      27
 
 #define INT_CLK         (1u << INT_V_CLK)
 #define INT_RQ          (1u << INT_V_RQ)
@@ -368,6 +370,8 @@ typedef struct {
 #define INT_QVSS        (1u << INT_V_QVSS)
 #define INT_DMCRX       (1u << INT_V_DMCRX)
 #define INT_DMCTX       (1u << INT_V_DMCTX)
+#define INT_DUPRX       (1u << INT_V_DUPRX)
+#define INT_DUPTX       (1u << INT_V_DUPTX)
 #define INT_TDRX        (1u << INT_V_TDRX)
 #define INT_TDTX        (1u << INT_V_TDTX)
 
@@ -396,6 +400,8 @@ typedef struct {
 #define IPL_QVSS        (0x14 - IPL_HMIN)
 #define IPL_DMCRX       (0x14 - IPL_HMIN)
 #define IPL_DMCTX       (0x14 - IPL_HMIN)
+#define IPL_DUPRX       (0x14 - IPL_HMIN)
+#define IPL_DUPTX       (0x14 - IPL_HMIN)
 #define IPL_TDRX        (0x14 - IPL_HMIN)
 #define IPL_TDTX        (0x14 - IPL_HMIN)
 
diff --git a/VAX/vax630_syslist.c b/VAX/vax630_syslist.c
index a02f81d9..de0ba4e2 100644
--- a/VAX/vax630_syslist.c
+++ b/VAX/vax630_syslist.c
@@ -68,6 +68,7 @@ extern DEVICE va_dev;
 extern DEVICE vc_dev;
 extern DEVICE lk_dev;
 extern DEVICE vs_dev;
+extern DEVICE dpv_dev;
 
 DEVICE *sim_devices[] = { 
     &cpu_dev,
@@ -100,6 +101,9 @@ DEVICE *sim_devices[] = {
     &tq_dev,
     &xq_dev,
     &xqb_dev,
+#if !defined(VAX_620)
+    &dpv_dev,
+#endif
     NULL
     };
 
diff --git a/VAX/vax730_syslist.c b/VAX/vax730_syslist.c
index cc80141d..c3976a0b 100644
--- a/VAX/vax730_syslist.c
+++ b/VAX/vax730_syslist.c
@@ -61,6 +61,7 @@ extern DEVICE dz_dev;
 extern DEVICE vh_dev;
 extern DEVICE xu_dev, xub_dev;
 extern DEVICE dmc_dev;
+extern DEVICE dup_dev;
 extern DEVICE ch_dev;
 
 DEVICE *sim_devices[] = { 
@@ -94,6 +95,7 @@ DEVICE *sim_devices[] = {
     &xu_dev,
     &xub_dev,
     &dmc_dev,
+    &dup_dev,
     &ch_dev,
     NULL
     };
diff --git a/VAX/vax750_syslist.c b/VAX/vax750_syslist.c
index 8cb5afa0..3861431e 100644
--- a/VAX/vax750_syslist.c
+++ b/VAX/vax750_syslist.c
@@ -63,6 +63,7 @@ extern DEVICE dz_dev;
 extern DEVICE vh_dev;
 extern DEVICE xu_dev, xub_dev;
 extern DEVICE dmc_dev;
+extern DEVICE dup_dev;
 extern DEVICE ch_dev;
 
 DEVICE *sim_devices[] = { 
@@ -99,6 +100,7 @@ DEVICE *sim_devices[] = {
     &xu_dev,
     &xub_dev,
     &dmc_dev,
+    &dup_dev,
     &ch_dev,
     NULL
     };
diff --git a/VAX/vax780_syslist.c b/VAX/vax780_syslist.c
index 45eb151d..133c3604 100644
--- a/VAX/vax780_syslist.c
+++ b/VAX/vax780_syslist.c
@@ -63,6 +63,7 @@ extern DEVICE dz_dev;
 extern DEVICE vh_dev;
 extern DEVICE xu_dev, xub_dev;
 extern DEVICE dmc_dev;
+extern DEVICE dup_dev;
 extern DEVICE ch_dev;
 
 DEVICE *sim_devices[] = { 
@@ -100,6 +101,7 @@ DEVICE *sim_devices[] = {
     &xu_dev,
     &xub_dev,
     &dmc_dev,
+    &dup_dev,
     &ch_dev,
     NULL
     };
diff --git a/VAX/vax820_syslist.c b/VAX/vax820_syslist.c
index 3597a8b5..6d8f37ea 100644
--- a/VAX/vax820_syslist.c
+++ b/VAX/vax820_syslist.c
@@ -60,6 +60,7 @@ extern DEVICE dz_dev;
 extern DEVICE vh_dev;
 extern DEVICE xu_dev, xub_dev;
 extern DEVICE dmc_dev;
+extern DEVICE dup_dev;
 extern DEVICE ch_dev;
 
 extern UNIT cpu_unit;
@@ -100,6 +101,7 @@ DEVICE *sim_devices[] = {
     &xu_dev,
     &xub_dev,
     &dmc_dev,
+    &dup_dev,
     &ch_dev,
     NULL
     };
diff --git a/VAX/vax860_syslist.c b/VAX/vax860_syslist.c
index b4008856..c02520f4 100644
--- a/VAX/vax860_syslist.c
+++ b/VAX/vax860_syslist.c
@@ -63,6 +63,7 @@ extern DEVICE dz_dev;
 extern DEVICE vh_dev;
 extern DEVICE xu_dev, xub_dev;
 extern DEVICE dmc_dev;
+extern DEVICE dup_dev;
 extern DEVICE ch_dev;
 
 DEVICE *sim_devices[] = { 
@@ -99,6 +100,7 @@ DEVICE *sim_devices[] = {
     &xu_dev,
     &xub_dev,
     &dmc_dev,
+    &dup_dev,
     &ch_dev,
     NULL
     };
diff --git a/VAX/vax_syslist.c b/VAX/vax_syslist.c
index b31995e3..bc26fa52 100644
--- a/VAX/vax_syslist.c
+++ b/VAX/vax_syslist.c
@@ -59,6 +59,7 @@ extern DEVICE vh_dev;
 extern DEVICE vc_dev;
 extern DEVICE lk_dev;
 extern DEVICE vs_dev;
+extern DEVICE dpv_dev;
 
 extern UNIT cpu_unit;
 
@@ -93,6 +94,7 @@ DEVICE *sim_devices[] = {
     &tq_dev,
     &xq_dev,
     &xqb_dev,
+    &dpv_dev,
     NULL
     };
 
diff --git a/VAX/vaxmod_defs.h b/VAX/vaxmod_defs.h
index 5ce0f5f8..59e441d0 100644
--- a/VAX/vaxmod_defs.h
+++ b/VAX/vaxmod_defs.h
@@ -368,8 +368,10 @@ typedef struct {
 #define INT_V_QVSS      21                              /* QVSS */
 #define INT_V_DMCRX     22                              /* DMC11 */
 #define INT_V_DMCTX     23
-#define INT_V_TDRX      24                              /* TU58 */
-#define INT_V_TDTX      25
+#define INT_V_DUPRX     24                              /* DPV11 */
+#define INT_V_DUPTX     25
+#define INT_V_TDRX      26                              /* TU58 */
+#define INT_V_TDTX      27
 
 #define INT_CLK         (1u << INT_V_CLK)
 #define INT_RQ          (1u << INT_V_RQ)
@@ -396,6 +398,8 @@ typedef struct {
 #define INT_QVSS        (1u << INT_V_QVSS)
 #define INT_DMCRX       (1u << INT_V_DMCRX)
 #define INT_DMCTX       (1u << INT_V_DMCTX)
+#define INT_DUPRX       (1u << INT_V_DUPRX)
+#define INT_DUPTX       (1u << INT_V_DUPTX)
 #define INT_TDRX        (1u << INT_V_TDRX)
 #define INT_TDTX        (1u << INT_V_TDTX)
 
@@ -424,6 +428,8 @@ typedef struct {
 #define IPL_QVSS        (0x14 - IPL_HMIN)
 #define IPL_DMCRX       (0x14 - IPL_HMIN)
 #define IPL_DMCTX       (0x14 - IPL_HMIN)
+#define IPL_DUPRX       (0x14 - IPL_HMIN)
+#define IPL_DUPTX       (0x14 - IPL_HMIN)
 #define IPL_TDRX        (0x14 - IPL_HMIN)
 #define IPL_TDTX        (0x14 - IPL_HMIN)
 
diff --git a/Visual Studio Projects/MicroVAX2.vcproj b/Visual Studio Projects/MicroVAX2.vcproj
index 849569bd..bf8c664e 100644
--- a/Visual Studio Projects/MicroVAX2.vcproj	
+++ b/Visual Studio Projects/MicroVAX2.vcproj	
@@ -200,6 +200,10 @@
 				RelativePath="..\PDP11\pdp11_cr.c"
 				>
 			</File>
+			<File
+				RelativePath="..\PDP11\pdp11_dup.c"
+				>
+			</File>
 			<File
 				RelativePath="..\PDP11\pdp11_dz.c"
 				>
@@ -560,6 +564,10 @@
 				RelativePath="..\PDP11\pdp11_cr_dat.h"
 				>
 			</File>
+			<File
+				RelativePath="..\PDP11\pdp11_dup.h"
+				>
+			</File>
 			<File
 				RelativePath="..\PDP11\pdp11_io_lib.h"
 				>
diff --git a/Visual Studio Projects/VAX.vcproj b/Visual Studio Projects/VAX.vcproj
index d03128b3..24aaceb5 100644
--- a/Visual Studio Projects/VAX.vcproj	
+++ b/Visual Studio Projects/VAX.vcproj	
@@ -95,7 +95,7 @@
 			<Tool
 				Name="VCPostBuildEventTool"
 				Description="Copy result to Model based binary name (MicroVAX3900.exe)"
-				CommandLine="if exist &quot;$(TargetPath)&quot; copy &quot;$(TargetPath)&quot; &quot;$(TargetDir)MicroVAX3900$(TargetExt)&quot; &#x0D;&#x0A;Post-Build-Event.cmd VAX &quot;$(TargetDir)$(TargetName).exe&quot; vax-diag_test"
+				CommandLine="if exist &quot;$(TargetPath)&quot; copy &quot;$(TargetPath)&quot; &quot;$(TargetDir)MicroVAX3900$(TargetExt)&quot;&#x0D;&#x0A;Post-Build-Event.cmd VAX &quot;$(TargetDir)$(TargetName).exe&quot; vax-diag_test&#x0D;&#x0A;"
 			/>
 		</Configuration>
 		<Configuration
@@ -185,7 +185,7 @@
 			<Tool
 				Name="VCPostBuildEventTool"
 				Description="Copy result to Model based binary name (MicroVAX3900.exe)"
-				CommandLine="if exist &quot;$(TargetPath)&quot; copy &quot;$(TargetPath)&quot; &quot;$(TargetDir)MicroVAX3900$(TargetExt)&quot; &#x0D;&#x0A;Post-Build-Event.cmd VAX &quot;$(TargetDir)$(TargetName).exe&quot; vax-diag_test"
+				CommandLine="if exist &quot;$(TargetPath)&quot; copy &quot;$(TargetPath)&quot; &quot;$(TargetDir)MicroVAX3900$(TargetExt)&quot;&#x0D;&#x0A;Post-Build-Event.cmd VAX &quot;$(TargetDir)$(TargetName).exe&quot; vax-diag_test&#x0D;&#x0A;"
 			/>
 		</Configuration>
 	</Configurations>
@@ -200,6 +200,10 @@
 				RelativePath="..\PDP11\pdp11_cr.c"
 				>
 			</File>
+			<File
+				RelativePath="..\PDP11\pdp11_dup.c"
+				>
+			</File>
 			<File
 				RelativePath="..\PDP11\pdp11_dz.c"
 				>
@@ -548,6 +552,10 @@
 				RelativePath="..\PDP11\pdp11_cr_dat.h"
 				>
 			</File>
+			<File
+				RelativePath="..\PDP11\pdp11_dup.h"
+				>
+			</File>
 			<File
 				RelativePath="..\PDP11\pdp11_io_lib.h"
 				>
diff --git a/Visual Studio Projects/VAX730.vcproj b/Visual Studio Projects/VAX730.vcproj
index cca0f88d..a37917cb 100644
--- a/Visual Studio Projects/VAX730.vcproj	
+++ b/Visual Studio Projects/VAX730.vcproj	
@@ -206,6 +206,10 @@
 				RelativePath="..\PDP11\pdp11_dmc.c"
 				>
 			</File>
+			<File
+				RelativePath="..\PDP11\pdp11_dup.c"
+				>
+			</File>
 			<File
 				RelativePath="..\PDP11\pdp11_dz.c"
 				>
diff --git a/Visual Studio Projects/VAX750.vcproj b/Visual Studio Projects/VAX750.vcproj
index a01add38..386a0c8a 100644
--- a/Visual Studio Projects/VAX750.vcproj	
+++ b/Visual Studio Projects/VAX750.vcproj	
@@ -206,6 +206,10 @@
 				RelativePath="..\PDP11\pdp11_dmc.c"
 				>
 			</File>
+			<File
+				RelativePath="..\PDP11\pdp11_dup.c"
+				>
+			</File>
 			<File
 				RelativePath="..\PDP11\pdp11_dz.c"
 				>
diff --git a/Visual Studio Projects/VAX780.vcproj b/Visual Studio Projects/VAX780.vcproj
index de7d682c..04ba7fb6 100644
--- a/Visual Studio Projects/VAX780.vcproj	
+++ b/Visual Studio Projects/VAX780.vcproj	
@@ -206,6 +206,10 @@
 				RelativePath="..\PDP11\pdp11_dmc.c"
 				>
 			</File>
+			<File
+				RelativePath="..\PDP11\pdp11_dup.c"
+				>
+			</File>
 			<File
 				RelativePath="..\PDP11\pdp11_dz.c"
 				>
diff --git a/Visual Studio Projects/VAX8200.vcproj b/Visual Studio Projects/VAX8200.vcproj
index d4c2e1a7..8c2b54bf 100644
--- a/Visual Studio Projects/VAX8200.vcproj	
+++ b/Visual Studio Projects/VAX8200.vcproj	
@@ -206,6 +206,10 @@
 				RelativePath="..\PDP11\pdp11_dmc.c"
 				>
 			</File>
+			<File
+				RelativePath="..\PDP11\pdp11_dup.c"
+				>
+			</File>
 			<File
 				RelativePath="..\PDP11\pdp11_dz.c"
 				>
diff --git a/Visual Studio Projects/VAX8600.vcproj b/Visual Studio Projects/VAX8600.vcproj
index 139b18be..03835b26 100644
--- a/Visual Studio Projects/VAX8600.vcproj	
+++ b/Visual Studio Projects/VAX8600.vcproj	
@@ -206,6 +206,10 @@
 				RelativePath="..\PDP11\pdp11_dmc.c"
 				>
 			</File>
+			<File
+				RelativePath="..\PDP11\pdp11_dup.c"
+				>
+			</File>
 			<File
 				RelativePath="..\PDP11\pdp11_dz.c"
 				>
diff --git a/descrip.mms b/descrip.mms
index 2119b06d..f51d924c 100644
--- a/descrip.mms
+++ b/descrip.mms
@@ -805,7 +805,7 @@ VAX_SOURCE2 = $(PDP11_DIR)PDP11_IO_LIB.C,\
               $(PDP11_DIR)PDP11_TS.C,$(PDP11_DIR)PDP11_DZ.C,\
               $(PDP11_DIR)PDP11_LP.C,$(PDP11_DIR)PDP11_TD.C,$(PDP11_DIR)PDP11_TQ.C,\
               $(PDP11_DIR)PDP11_XQ.C,$(PDP11_DIR)PDP11_VH.C,\
-              $(PDP11_DIR)PDP11_CR.C,\
+              $(PDP11_DIR)PDP11_CR.C,$(PDP11_DIR)PDP11_DUP.C,\
               $(VAX_DIR)VAX_VC.C,$(VAX_DIR)VAX_LK.C,\
               $(VAX_DIR)VAX_VS.C,$(VAX_DIR)VAX_2681.C
 .IFDEF ALPHA_OR_IA64
@@ -1157,7 +1157,7 @@ VAX610_SOURCE2 = $(PDP11_DIR)PDP11_IO_LIB.C,\
                  $(PDP11_DIR)PDP11_XQ.C,$(PDP11_DIR)PDP11_VH.C,\
                  $(PDP11_DIR)PDP11_CR.C,$(VAX610_DIR)VAX_VC.C,\
                  $(VAX610_DIR)VAX_LK.C,$(VAX610_DIR)VAX_VS.C,\
-                 $(VAX610_DIR)VAX_2681.C
+                 $(VAX610_DIR)VAX_2681.C,$(PDP11_DIR)PDP11_DUP.C
 .IFDEF ALPHA_OR_IA64
 VAX610_OPTIONS = /INCL=($(SIMH_DIR),$(VAX610_DIR),$(PDP11_DIR)$(PCAP_INC))\
                  /DEF=($(CC_DEFS),"VM_VAX=1","USE_ADDR64=1","USE_INT64=1"$(PCAP_DEFS),"VAX_610=1")
@@ -1185,7 +1185,7 @@ VAX630_SOURCE2 = $(PDP11_DIR)PDP11_IO_LIB.C,$(PDP11_DIR)PDP11_CR.C,\
                  $(PDP11_DIR)PDP11_TS.C,$(PDP11_DIR)PDP11_DZ.C,\
                  $(PDP11_DIR)PDP11_LP.C,$(PDP11_DIR)PDP11_TD.C,\
                  $(PDP11_DIR)PDP11_TQ.C,$(PDP11_DIR)PDP11_XQ.C,\
-                 $(PDP11_DIR)PDP11_VH.C,\
+                 $(PDP11_DIR)PDP11_VH.C,$(PDP11_DIR)PDP11_DUP.C,\
                  $(VAX630_DIR)VAX_VA.C,$(VAX630_DIR)VAX_VC.C,\
                  $(VAX630_DIR)VAX_LK.C,$(VAX630_DIR)VAX_VS.C,\
                  $(VAX630_DIR)VAX_2681.C,$(VAX630_DIR)VAX_GPX.C
@@ -1218,7 +1218,7 @@ VAX620_SOURCE2 = $(PDP11_DIR)PDP11_IO_LIB.C,\
                  $(PDP11_DIR)PDP11_XQ.C,$(PDP11_DIR)PDP11_VH.C,\
                  $(PDP11_DIR)PDP11_CR.C,$(VAX620_DIR)VAX_VC.C,\
                  $(VAX620_DIR)VAX_LK.C,$(VAX620_DIR)VAX_VS.C,\
-                 $(VAX620_DIR)VAX_2681.C
+                 $(VAX620_DIR)VAX_2681.C,$(PDP11_DIR)PDP11_DUP.C
 .IFDEF ALPHA_OR_IA64
 VAX620_OPTIONS = /INCL=($(SIMH_DIR),$(VAX620_DIR),$(PDP11_DIR)$(PCAP_INC))\
                  /DEF=($(CC_DEFS),"VM_VAX=1","USE_ADDR64=1","USE_INT64=1"$(PCAP_DEFS),"VAX_620=1")
@@ -1249,7 +1249,8 @@ VAX730_SOURCE2 = $(PDP11_DIR)PDP11_RL.C,$(PDP11_DIR)PDP11_RQ.C,\
                  $(PDP11_DIR)PDP11_CR.C,$(PDP11_DIR)PDP11_HK.C,\
                  $(PDP11_DIR)PDP11_VH.C,$(PDP11_DIR)PDP11_DMC.C,\
                  $(PDP11_DIR)PDP11_TC.C,$(PDP11_DIR)PDP11_RK.C,\
-                 $(PDP11_DIR)PDP11_CH.C,$(PDP11_DIR)PDP11_IO_LIB.C
+                 $(PDP11_DIR)PDP11_CH.C,$(PDP11_DIR)PDP11_IO_LIB.C,\
+                 $(PDP11_DIR)PDP11_DUP.C
 .IFDEF ALPHA_OR_IA64
 VAX730_OPTIONS = /INCL=($(SIMH_DIR),$(VAX730_DIR),$(PDP11_DIR)$(PCAP_INC))\
                  /DEF=($(CC_DEFS),"VM_VAX=1","USE_ADDR64=1","USE_INT64=1"$(PCAP_DEFS),"VAX_730=1")
@@ -1281,7 +1282,8 @@ VAX750_SOURCE2 = $(PDP11_DIR)PDP11_RL.C,$(PDP11_DIR)PDP11_RQ.C,\
                  $(PDP11_DIR)PDP11_RP.C,$(PDP11_DIR)PDP11_TU.C,\
                  $(PDP11_DIR)PDP11_VH.C,$(PDP11_DIR)PDP11_DMC.C,\
                  $(PDP11_DIR)PDP11_TC.C,$(PDP11_DIR)PDP11_RK.C,\
-                 $(PDP11_DIR)PDP11_CH.C,$(PDP11_DIR)PDP11_IO_LIB.C
+                 $(PDP11_DIR)PDP11_CH.C,$(PDP11_DIR)PDP11_IO_LIB.C,\
+                 $(PDP11_DIR)PDP11_DUP.C
 .IFDEF ALPHA_OR_IA64
 VAX750_OPTIONS = /INCL=($(SIMH_DIR),$(VAX750_DIR),$(PDP11_DIR)$(PCAP_INC))\
                  /DEF=($(CC_DEFS),"VM_VAX=1","USE_ADDR64=1","USE_INT64=1"$(PCAP_DEFS),"VAX_750=1")
@@ -1313,7 +1315,8 @@ VAX780_SOURCE2 = $(PDP11_DIR)PDP11_RL.C,$(PDP11_DIR)PDP11_RQ.C,\
                  $(PDP11_DIR)PDP11_TU.C,$(PDP11_DIR)PDP11_HK.C,\
                  $(PDP11_DIR)PDP11_VH.C,$(PDP11_DIR)PDP11_DMC.C,\
                  $(PDP11_DIR)PDP11_TC.C,$(PDP11_DIR)PDP11_RK.C,\
-                 $(PDP11_DIR)PDP11_CH.C,$(PDP11_DIR)PDP11_IO_LIB.C
+                 $(PDP11_DIR)PDP11_CH.C,$(PDP11_DIR)PDP11_IO_LIB.C,\
+                 $(PDP11_DIR)PDP11_DUP.C
 .IFDEF ALPHA_OR_IA64
 VAX780_OPTIONS = /INCL=($(SIMH_DIR),$(VAX780_DIR),$(PDP11_DIR)$(PCAP_INC))\
                  /DEF=($(CC_DEFS),"VM_VAX=1","USE_ADDR64=1","USE_INT64=1"$(PCAP_DEFS),"VAX_780=1")
@@ -1344,7 +1347,8 @@ VAX8200_SOURCE2 = $(PDP11_DIR)PDP11_RL.C,$(PDP11_DIR)PDP11_RQ.C,\
                  $(PDP11_DIR)PDP11_CR.C,$(PDP11_DIR)PDP11_HK.C,\
                  $(PDP11_DIR)PDP11_VH.C,$(PDP11_DIR)PDP11_DMC.C,\
                  $(PDP11_DIR)PDP11_TC.C,$(PDP11_DIR)PDP11_RK.C,\
-                 $(PDP11_DIR)PDP11_CH.C,$(PDP11_DIR)PDP11_IO_LIB.C
+                 $(PDP11_DIR)PDP11_CH.C,$(PDP11_DIR)PDP11_IO_LIB.C,\
+                 $(PDP11_DIR)PDP11_DUP.C
 .IFDEF ALPHA_OR_IA64
 VAX8200_OPTIONS = /INCL=($(SIMH_DIR),$(VAX8200_DIR),$(PDP11_DIR)$(PCAP_INC))\
                  /DEF=($(CC_DEFS),"VM_VAX=1","USE_ADDR64=1","USE_INT64=1"$(PCAP_DEFS),"VAX_820=1")
@@ -1376,7 +1380,8 @@ VAX8600_SOURCE2 = $(PDP11_DIR)PDP11_RL.C,$(PDP11_DIR)PDP11_RQ.C,\
                  $(PDP11_DIR)PDP11_TU.C,$(PDP11_DIR)PDP11_HK.C,\
                  $(PDP11_DIR)PDP11_VH.C,$(PDP11_DIR)PDP11_DMC.C,\
                  $(PDP11_DIR)PDP11_TC.C,$(PDP11_DIR)PDP11_RK.C,\
-                 $(PDP11_DIR)PDP11_CH.C,$(PDP11_DIR)PDP11_IO_LIB.C
+                 $(PDP11_DIR)PDP11_CH.C,$(PDP11_DIR)PDP11_IO_LIB.C,\
+                 $(PDP11_DIR)PDP11_DUP.C
 .IFDEF ALPHA_OR_IA64
 VAX8600_OPTIONS = /INCL=($(SIMH_DIR),$(VAX8600_DIR),$(PDP11_DIR)$(PCAP_INC))\
                  /DEF=($(CC_DEFS),"VM_VAX=1","USE_ADDR64=1","USE_INT64=1"$(PCAP_DEFS),"VAX_860=1")
diff --git a/makefile b/makefile
index d723b581..aee48b36 100644
--- a/makefile
+++ b/makefile
@@ -1399,7 +1399,7 @@ VAX = ${VAXD}/vax_cpu.c ${VAXD}/vax_cpu1.c ${VAXD}/vax_fpa.c ${VAXD}/vax_io.c \
 	${PDP11D}/pdp11_rl.c ${PDP11D}/pdp11_rq.c ${PDP11D}/pdp11_ts.c \
 	${PDP11D}/pdp11_dz.c ${PDP11D}/pdp11_lp.c ${PDP11D}/pdp11_tq.c \
 	${PDP11D}/pdp11_xq.c ${PDP11D}/pdp11_vh.c ${PDP11D}/pdp11_cr.c \
-	${PDP11D}/pdp11_td.c ${PDP11D}/pdp11_io_lib.c
+	${PDP11D}/pdp11_td.c ${PDP11D}/pdp11_io_lib.c ${PDP11D}/pdp11_dup.c
 VAX_OPT = -DVM_VAX -DUSE_INT64 -DUSE_ADDR64 -DUSE_SIM_VIDEO -I ${VAXD} -I ${PDP11D} ${NETWORK_OPT} ${VIDEO_CCDEFS} ${VIDEO_LDFLAGS}
 
 
@@ -1485,7 +1485,7 @@ VAX630 = ${VAXD}/vax_cpu.c ${VAXD}/vax_cpu1.c ${VAXD}/vax_fpa.c \
 	${PDP11D}/pdp11_rl.c ${PDP11D}/pdp11_rq.c ${PDP11D}/pdp11_ts.c \
 	${PDP11D}/pdp11_dz.c ${PDP11D}/pdp11_lp.c ${PDP11D}/pdp11_tq.c \
 	${PDP11D}/pdp11_xq.c ${PDP11D}/pdp11_vh.c ${PDP11D}/pdp11_cr.c \
-	${PDP11D}/pdp11_td.c ${PDP11D}/pdp11_io_lib.c
+	${PDP11D}/pdp11_td.c ${PDP11D}/pdp11_io_lib.c ${PDP11D}/pdp11_dup.c
 VAX620_OPT = -DVM_VAX -DVAX_620 -DUSE_INT64 -DUSE_ADDR64 -I ${VAXD} -I ${PDP11D} ${NETWORK_OPT}
 VAX630_OPT = -DVM_VAX -DVAX_630 -DUSE_INT64 -DUSE_ADDR64 -DUSE_SIM_VIDEO -I ${VAXD} -I ${PDP11D} ${NETWORK_OPT} ${VIDEO_CCDEFS} ${VIDEO_LDFLAGS}
 
@@ -1501,7 +1501,7 @@ VAX730 = ${VAXD}/vax_cpu.c ${VAXD}/vax_cpu1.c ${VAXD}/vax_fpa.c \
 	${PDP11D}/pdp11_xu.c ${PDP11D}/pdp11_ry.c ${PDP11D}/pdp11_cr.c \
 	${PDP11D}/pdp11_hk.c ${PDP11D}/pdp11_vh.c ${PDP11D}/pdp11_dmc.c \
 	${PDP11D}/pdp11_td.c ${PDP11D}/pdp11_tc.c ${PDP11D}/pdp11_rk.c \
-	${PDP11D}/pdp11_io_lib.c ${PDP11D}/pdp11_ch.c
+	${PDP11D}/pdp11_io_lib.c ${PDP11D}/pdp11_ch.c ${PDP11D}/pdp11_dup.c
 VAX730_OPT = -DVM_VAX -DVAX_730 -DUSE_INT64 -DUSE_ADDR64 -I VAX -I ${PDP11D} ${NETWORK_OPT}
 
 
@@ -1548,7 +1548,7 @@ VAX8200 = ${VAXD}/vax_cpu.c ${VAXD}/vax_cpu1.c ${VAXD}/vax_fpa.c \
 	${PDP11D}/pdp11_xu.c ${PDP11D}/pdp11_ry.c ${PDP11D}/pdp11_cr.c \
 	${PDP11D}/pdp11_hk.c ${PDP11D}/pdp11_vh.c ${PDP11D}/pdp11_dmc.c \
 	${PDP11D}/pdp11_td.c ${PDP11D}/pdp11_tc.c ${PDP11D}/pdp11_rk.c \
-	${PDP11D}/pdp11_io_lib.c ${PDP11D}/pdp11_ch.c
+	${PDP11D}/pdp11_io_lib.c ${PDP11D}/pdp11_ch.c ${PDP11D}/pdp11_dup.c
 VAX8200_OPT = -DVM_VAX -DVAX_820 -DUSE_INT64 -DUSE_ADDR64 -I VAX -I ${PDP11D} ${NETWORK_OPT}