diff --git a/VAX/vax_cpu.c b/VAX/vax_cpu.c
index e6ace209..b4a69ee4 100644
--- a/VAX/vax_cpu.c
+++ b/VAX/vax_cpu.c
@@ -227,6 +227,12 @@
                             R[rn] = rl; \
                             R[rn + 1] = rh; \
                             }
+#define CHECK_FOR_IDLE_LOOP if (PC == fault_PC) {                           /* to self? */ \
+                                if (PSL_GETIPL (PSL) == 0x1F)               /* int locked out? */ \
+                                    ABORT (STOP_LOOP);                      /* infinite loop */ \
+                                cpu_idle ();                                /* idle loop */ \
+                                }
+
 
 #define HIST_MIN        64
 #define HIST_MAX        65536
@@ -491,7 +497,7 @@ REG cpu_reg[] = {
 MTAB cpu_mod[] = {
     { UNIT_CONH, 0, "HALT to SIMH", "SIMHALT", NULL, NULL, NULL, "Set HALT to trap to simulator" },
     { UNIT_CONH, UNIT_CONH, "HALT to console", "CONHALT", NULL, NULL, NULL, "Set HALT to trap to console ROM" },
-    { MTAB_XTD|MTAB_VDV, 0, "IDLE", "IDLE={VMS|ULTRIX|NETBSD|OPENBSD|ULTRIXOLD|OPENBSDOLD|QUASIJARUS|32V|SYSV|ALL}", &cpu_set_idle, &cpu_show_idle, NULL, "Display idle detection mode" },
+    { MTAB_XTD|MTAB_VDV, 0, "IDLE", "IDLE={VMS|ULTRIX|NETBSD|OPENBSD|ULTRIXOLD|OPENBSDOLD|QUASIJARUS|32V|ALL}", &cpu_set_idle, &cpu_show_idle, NULL, "Display idle detection mode" },
     { MTAB_XTD|MTAB_VDV, 0, NULL, "NOIDLE", &sim_clr_idle, NULL, NULL,  "Disables idle detection" },
     MEM_MODIFIERS,   /* Model specific memory modifiers from vaxXXX_defs.h */
     { MTAB_XTD|MTAB_VDV|MTAB_NMO|MTAB_SHP, 0, "HISTORY", "HISTORY",
@@ -2184,20 +2190,12 @@ for ( ;; ) {
 
     case BRB:
         BRANCHB (brdisp);                               /* branch  */
-        if (PC == fault_PC) {                           /* to self? */
-            if (PSL_GETIPL (PSL) == 0x1F)               /* int locked out? */
-                ABORT (STOP_LOOP);                      /* infinite loop */
-            cpu_idle ();                                /* idle loop */
-            }
+        CHECK_FOR_IDLE_LOOP;
         break;
 
     case BRW:
         BRANCHW (brdisp);                               /* branch */
-        if (PC == fault_PC) {                           /* to self? */
-            if (PSL_GETIPL (PSL) == 0x1F)               /* int locked out? */
-                ABORT (STOP_LOOP);                      /* infinite loop */
-            cpu_idle ();                                /* idle loop */
-            }
+        CHECK_FOR_IDLE_LOOP;
         break;
 
     case BSBB:
@@ -2470,20 +2468,16 @@ for ( ;; ) {
         break;
 
     case BLBS:
-        if (op0 & 1)                                    /* br if bit set */
+        if (op0 & 1) {                                  /* br if bit set */
             BRANCHB (brdisp);
+            CHECK_FOR_IDLE_LOOP;
+            }
         break;
 
     case BLBC:
-        if ((op0 & 1) == 0)                             /* br if bit clear */
-            {
+        if ((op0 & 1) == 0) {                           /* br if bit clear */
             BRANCHB (brdisp);
-            if (((cpu_idle_mask & VAX_IDLE_SYSV) != 0) &&/* running System V? */
-                (PC == fault_PC) &&                     /*  to self? */
-                (fault_PC & 0x80000000) &&              /*  in system space? */
-                (PSL_GETIPL (PSL) == 0x0) &&            /*  at IPL 0? */
-                (PSL_GETCUR(PSL) == KERN))              /*  in Kernel Mode? */
-                cpu_idle ();                            /* idle loop */
+            CHECK_FOR_IDLE_LOOP;
             }
         break;
 
@@ -3546,8 +3540,7 @@ static struct os_idle os_tab[] = {
     { "OPENBSD", VAX_IDLE_BSDNEW },
     { "QUASIJARUS", VAX_IDLE_QUAD },
     { "32V", VAX_IDLE_QUAD },
-    { "SYSV", VAX_IDLE_SYSV },
-    { "ALL", VAX_IDLE_VMS|VAX_IDLE_ULTOLD|VAX_IDLE_ULT|VAX_IDLE_ULT1X|VAX_IDLE_QUAD|VAX_IDLE_BSDNEW|VAX_IDLE_SYSV },
+    { "ALL", VAX_IDLE_VMS|VAX_IDLE_ULTOLD|VAX_IDLE_ULT|VAX_IDLE_ULT1X|VAX_IDLE_QUAD|VAX_IDLE_BSDNEW },
     { NULL, 0 }
     };
 
@@ -3651,7 +3644,7 @@ fprintf (st, "      -u      interpret address as virtual, user mode\n\n");
 fprintf (st, "The CPU attempts to detect when the simulator is idle.  When idle, the\n");
 fprintf (st, "simulator does not use any resources on the host system.  Idle detection is\n");
 fprintf (st, "controlled by the SET IDLE and SET NOIDLE commands:\n\n");
-fprintf (st, "   sim> SET CPU IDLE{=VMS|ULTRIX|NETBSD|FREEBSD|32V|SYSV|ALL}\n");
+fprintf (st, "   sim> SET CPU IDLE{=VMS|ULTRIX|NETBSD|FREEBSD|32V|ALL}\n");
 fprintf (st, "                                        enable idle detection\n");
 fprintf (st, "   sim> SET CPU NOIDLE                  disable idle detection\n\n");
 fprintf (st, "Idle detection is disabled by default.  Unless ALL is specified, idle\n");