diff --git a/Interdata/id_dp.c b/Interdata/id_dp.c
index 45be20a9..a33f0623 100644
--- a/Interdata/id_dp.c
+++ b/Interdata/id_dp.c
@@ -25,7 +25,7 @@
 
    dp           M46-421 2.5MB/10MB cartridge disk
 
-   01-Mar-20    RMS     Fixed xTIME register declarations (Mark Pizzolato)
+   01-Mar-20    RMS     Fixed xTIME register definitions (Mark Pizzolato)
    18-Mar-05    RMS     Added attached test to detach routine
    25-Jan-04    RMS     Revised for device debug support
    25-Apr-03    RMS     Revised for extended file support
diff --git a/sim_defs.h b/sim_defs.h
index aa5159e8..443935e3 100644
--- a/sim_defs.h
+++ b/sim_defs.h
@@ -116,6 +116,9 @@
 #include <stddef.h>
 #include <stdlib.h>
 #include <stdio.h>
+#if defined(_MSC_VER) && (_MSC_VER < 1900)
+#define snprintf _snprintf      /* poor man's snprintf which will work most of the time but has different return value */
+#endif
 #include <stdarg.h>
 #include <string.h>
 #include <errno.h>
@@ -542,6 +545,9 @@ struct sim_debtab {
 #define FLDATA(nm,loc,pos) #nm, &(loc), 2, 1, (pos), 1
 #define GRDATA(nm,loc,rdx,wd,pos) #nm, &(loc), (rdx), (wd), (pos), 1
 #define BRDATA(nm,loc,rdx,wd,dep) #nm, (loc), (rdx), (wd), 0, (dep)
+#define VBRDATA(nm,loc,rdx,wd,dep) #nm, (loc), (rdx), (wd), 0, (dep)
+#define SAVEDATA(nm,loc) \
+    #nm, &(loc), 8, 8, 0, sizeof(loc), REG_HRO
 #define URDATA(nm,loc,rdx,wd,off,dep,fl) \
     #nm, &(loc), (rdx), (wd), (off), (dep), ((fl) | REG_UNIT)
 #else
@@ -551,6 +557,9 @@ struct sim_debtab {
 #define FLDATA(nm,loc,pos) "nm", &(loc), 2, 1, (pos), 1
 #define GRDATA(nm,loc,rdx,wd,pos) "nm", &(loc), (rdx), (wd), (pos), 1
 #define BRDATA(nm,loc,rdx,wd,dep) "nm", (loc), (rdx), (wd), 0, (dep)
+#define VBRDATA(nm,loc,rdx,wd,dep) "nm", (loc), (rdx), (wd), 0, (dep)
+#define SAVEDATA(nm,loc) \
+    "nm", &(loc), 8, 8, 0, sizeof(loc), REG_HRO
 #define URDATA(nm,loc,rdx,wd,off,dep,fl) \
     "nm", &(loc), (rdx), (wd), (off), (dep), ((fl) | REG_UNIT)
 #endif
diff --git a/sim_rev.h b/sim_rev.h
index 7b12fbb3..327f6e83 100644
--- a/sim_rev.h
+++ b/sim_rev.h
@@ -29,7 +29,7 @@
 
 #define SIM_MAJOR       3
 #define SIM_MINOR       11
-#define SIM_PATCH       0
+#define SIM_PATCH       1
 #define SIM_DELTA       0
 
 /* V3.11 revision history
@@ -37,6 +37,30 @@
    V3.11 incorporates SCP additions and extensions by Dave Bryan to support his
    HP simulators.
 
+patch   date            module(s) and fix(es)
+
+  1     06-Mar-2020     scp.c and sim_tmxr_c
+                        - new extensions to support HP simulators
+
+                        sim_ether library
+                        - imported latest V4 revision
+
+                        Alpha
+                        - fixed DMAPEN register definition
+
+                        Interdata
+                        - fixed DP xTIME register definitions
+
+                        PDP-11
+                        - fixed PT INT definition
+                        - disabled VH11 (temporarily) because of multiline race condition
+
+                        Sigma
+                        - fixed incorrect 550 interrupt register array declaration
+
+                        VAX
+                        - disabled VH11 (temporarily) because of multiline race condition
+
 patch   date            module(s) and fix(es)
 
   0     01-Dec-2019     scp.c and supporting libraries