diff --git a/VAX/vax610_sysdev.c b/VAX/vax610_sysdev.c
index 44b36d0f..e1e01057 100644
--- a/VAX/vax610_sysdev.c
+++ b/VAX/vax610_sysdev.c
@@ -117,7 +117,8 @@ DEVICE sysd_dev = {
 
 CTAB vax610_cmd[] = {
     { "BOOT", &vax610_boot, RU_BOOT,
-      "bo{ot} <device>{/R5:flg} boot device\n", &run_cmd_message },
+      "bo{ot} <device>{/R5:flg} boot device\n"
+      "                         type HELP CPU to see bootable devices\n", &run_cmd_message },
     { NULL }
     };
 
@@ -336,8 +337,15 @@ t_stat vax610_boot (int32 flag, char *ptr)
 t_stat r;
 
 r = vax610_boot_parse (flag, ptr);                      /* parse the boot cmd */
-if (r != SCPE_OK)                                       /* error? */
+if (r != SCPE_OK) {                                     /* error? */
+    if (r >= SCPE_BASE) {                               /* message available? */
+        printf ("%s\n", sim_error_text (r));
+        if (sim_log)
+            fprintf (sim_log, "%s\n", sim_error_text (r));
+        r |= SCPE_NOMESSAGE;
+        }
     return r;
+    }
 strncpy (cpu_boot_cmd, ptr, CBUFSIZE);                  /* save for reboot */
 return run_cmd (flag, "CPU");
 }
diff --git a/VAX/vax730_sys.c b/VAX/vax730_sys.c
index a985d10d..f1891b31 100644
--- a/VAX/vax730_sys.c
+++ b/VAX/vax730_sys.c
@@ -140,7 +140,8 @@ DEVICE sysb_dev = {
 
 CTAB vax730_cmd[] = {
     { "BOOT", &vax730_boot, RU_BOOT,
-      "bo{ot} <device>{/R5:flg} boot device\n", &run_cmd_message },
+      "bo{ot} <device>{/R5:flg} boot device\n"
+      "                         type HELP CPU to see bootable devices\n", &run_cmd_message },
     { NULL }
     };
 
@@ -482,8 +483,15 @@ t_stat vax730_boot (int32 flag, char *ptr)
 t_stat r;
 
 r = vax730_boot_parse (flag, ptr);                      /* parse the boot cmd */
-if (r != SCPE_OK)                                       /* error? */
+if (r != SCPE_OK) {                                     /* error? */
+    if (r >= SCPE_BASE) {                               /* message available? */
+        printf ("%s\n", sim_error_text (r));
+        if (sim_log)
+            fprintf (sim_log, "%s\n", sim_error_text (r));
+        r |= SCPE_NOMESSAGE;
+        }
     return r;
+    }
 strncpy (cpu_boot_cmd, ptr, CBUFSIZE);                  /* save for reboot */
 return run_cmd (flag, "CPU");
 }
@@ -501,6 +509,8 @@ DIB *dibp;
 uint32 ba;
 t_stat r;
 
+if (!ptr || !*ptr)
+    return SCPE_2FARG;
 regptr = get_glyph (ptr, gbuf, 0);                      /* get glyph */
 if ((slptr = strchr (gbuf, '/'))) {                     /* found slash? */
     regptr = strchr (ptr, '/');                         /* locate orig */
diff --git a/VAX/vax750_cmi.c b/VAX/vax750_cmi.c
index 9bb950bb..3051a2af 100644
--- a/VAX/vax750_cmi.c
+++ b/VAX/vax750_cmi.c
@@ -167,7 +167,8 @@ DEVICE cmi_dev = {
 
 CTAB vax750_cmd[] = {
     { "BOOT", &vax750_boot, RU_BOOT,
-      "bo{ot} <device>{/R5:flg} boot device\n", &run_cmd_message },
+      "bo{ot} <device>{/R5:flg} boot device\n"
+      "                         type HELP CPU to see bootable devices\n", &run_cmd_message },
     { NULL }
     };
 
@@ -566,8 +567,15 @@ t_stat vax750_boot (int32 flag, char *ptr)
 t_stat r;
 
 r = vax750_boot_parse (flag, ptr);                      /* parse the boot cmd */
-if (r != SCPE_OK)                                       /* error? */
+if (r != SCPE_OK) {                                     /* error? */
+    if (r >= SCPE_BASE) {                               /* message available? */
+        printf ("%s\n", sim_error_text (r));
+        if (sim_log)
+            fprintf (sim_log, "%s\n", sim_error_text (r));
+        r |= SCPE_NOMESSAGE;
+        }
     return r;
+    }
 strncpy (cpu_boot_cmd, ptr, CBUFSIZE);                  /* save for reboot */
 return run_cmd (flag, "CPU");
 }
@@ -585,6 +593,8 @@ DIB *dibp;
 uint32 ba;
 t_stat r;
 
+if (!ptr || !*ptr)
+    return SCPE_2FARG;
 regptr = get_glyph (ptr, gbuf, 0);                      /* get glyph */
 if ((slptr = strchr (gbuf, '/'))) {                     /* found slash? */
     regptr = strchr (ptr, '/');                         /* locate orig */
diff --git a/VAX/vax780_sbi.c b/VAX/vax780_sbi.c
index 861a2b8d..f9b02e51 100644
--- a/VAX/vax780_sbi.c
+++ b/VAX/vax780_sbi.c
@@ -204,7 +204,8 @@ DEVICE sbi_dev = {
 
 CTAB vax780_cmd[] = {
     { "BOOT", &vax780_boot, RU_BOOT,
-      "bo{ot} <device>{/R5:flg} boot device\n", &run_cmd_message },
+      "bo{ot} <device>{/R5:flg} boot device\n"
+      "                         type HELP CPU to see bootable devices\n", &run_cmd_message },
     { "FLOAD", &vax780_fload, 0,
       "fl{oad} <file> {<start>} load file from console floppy\n" },
     { NULL }
@@ -631,8 +632,15 @@ t_stat vax780_boot (int32 flag, char *ptr)
 t_stat r;
 
 r = vax780_boot_parse (flag, ptr);                      /* parse the boot cmd */
-if (r != SCPE_OK)                                       /* error? */
+if (r != SCPE_OK) {                                     /* error? */
+    if (r >= SCPE_BASE) {                               /* message available? */
+        printf ("%s\n", sim_error_text (r));
+        if (sim_log)
+            fprintf (sim_log, "%s\n", sim_error_text (r));
+        r |= SCPE_NOMESSAGE;
+        }
     return r;
+    }
 strncpy (cpu_boot_cmd, ptr, CBUFSIZE);                  /* save for reboot */
 return run_cmd (flag, "CPU");
 }
@@ -649,6 +657,8 @@ UNIT *uptr;
 DIB *dibp;
 t_stat r;
 
+if (!ptr || !*ptr)
+    return SCPE_2FARG;
 regptr = get_glyph (ptr, gbuf, 0);                      /* get glyph */
 if ((slptr = strchr (gbuf, '/'))) {                     /* found slash? */
     regptr = strchr (ptr, '/');                         /* locate orig */
diff --git a/VAX/vax860_abus.c b/VAX/vax860_abus.c
index 6f82d615..d004aa85 100644
--- a/VAX/vax860_abus.c
+++ b/VAX/vax860_abus.c
@@ -186,7 +186,8 @@ DEVICE abus_dev = {
 
 CTAB vax860_cmd[] = {
     { "BOOT", &vax860_boot, RU_BOOT,
-      "bo{ot} <device>{/R5:flg} boot device\n", &run_cmd_message },
+      "bo{ot} <device>{/R5:flg} boot device\n"
+      "                         type HELP CPU to see bootable devices\n", &run_cmd_message },
     { NULL }
     };
 
@@ -591,8 +592,15 @@ t_stat vax860_boot (int32 flag, char *ptr)
 t_stat r;
 
 r = vax860_boot_parse (flag, ptr);                      /* parse the boot cmd */
-if (r != SCPE_OK)                                       /* error? */
+if (r != SCPE_OK) {                                     /* error? */
+    if (r >= SCPE_BASE) {                               /* message available? */
+        printf ("%s\n", sim_error_text (r));
+        if (sim_log)
+            fprintf (sim_log, "%s\n", sim_error_text (r));
+        r |= SCPE_NOMESSAGE;
+        }
     return r;
+    }
 strncpy (cpu_boot_cmd, ptr, CBUFSIZE);                  /* save for reboot */
 return run_cmd (flag, "CPU");
 }
@@ -610,6 +618,8 @@ DIB *dibp;
 uint32 ba;
 t_stat r;
 
+if (!ptr || !*ptr)
+    return SCPE_2FARG;
 regptr = get_glyph (ptr, gbuf, 0);                      /* get glyph */
 if ((slptr = strchr (gbuf, '/'))) {                     /* found slash? */
     regptr = strchr (ptr, '/');                         /* locate orig */
diff --git a/scp.c b/scp.c
index e3d54e90..c96b08c2 100644
--- a/scp.c
+++ b/scp.c
@@ -1236,9 +1236,16 @@ if (*cptr) {
                                 dptr->attach_help (sim_log, dptr, uptr, 0, cptr);
                             }
                         else {
-                            helps[i].attach_help (stdout, dptr, uptr, 0, cptr);
-                            if (sim_log)
-                                helps[i].attach_help (sim_log, dptr, uptr, 0, cptr);
+                            if (helps[i].attach_help) {
+                                helps[i].attach_help (stdout, dptr, uptr, 0, cptr);
+                                if (sim_log)
+                                    helps[i].attach_help (sim_log, dptr, uptr, 0, cptr);
+                                }
+                            else {
+                                fprintf (stdout, "No help available for the %s device ATTACH command\n", dptr->name, cmdp->name);
+                                if (sim_log)
+                                    fprintf (sim_log, "No help available for the %s device ATTACH command\n", dptr->name, cmdp->name);
+                                }
                             }
                         }
                     }