diff --git a/sigma/sigma_cpu.c b/sigma/sigma_cpu.c
index 6064e924..1f73e564 100644
--- a/sigma/sigma_cpu.c
+++ b/sigma/sigma_cpu.c
@@ -316,6 +316,7 @@ MTAB cpu_mod[] = {
     { CPUF_MODEL, CPUF_S5, "Sigma 5", "SIGMA5", &cpu_set_type },
     { CPUF_MODEL, CPUF_S6, "Sigma 6", "SIGMA6", &cpu_set_type },
     { CPUF_MODEL, CPUF_S7, "Sigma 7", "SIGMA7", &cpu_set_type },
+    { CPUF_MODEL, CPUF_S7B, "Sigma 7 BigMem", "SIGMA7B", & cpu_set_type },
 //    { CPUF_MODEL, CPUF_S8, "Sigma 8", "SIGMA8", &cpu_set_type },
 //    { CPUF_MODEL, CPUF_S9, "Sigma 9", "SIGMA9", &cpu_set_type },
 //    { CPUF_MODEL, CPUF_550, "550", "550", &cpu_set_type },
@@ -396,6 +397,8 @@ cpu_var_t cpu_tab[] = {
       CC1|CC2,      CPUF_STR|CPUF_MAP|CPUF_WLK|CPUF_DEC,    CPUF_FP|CPUF_LAMS },
     { 0x080E0000,   0xC8FFFE0F, 0x0FC,  PAMASK17,   14,     8,  /* S7 */
       CC1|CC2,      CPUF_STR|CPUF_MAP|CPUF_WLK,     CPUF_FP|CPUF_DEC|CPUF_LAMS },
+    { 0x080E0000,   0xC8FFFE0F, 0x0FC,  PAMASK20,   14,     8,  /* S7B */
+      CC1|CC2,      CPUF_STR|CPUF_MAP|CPUF_WLK,     CPUF_FP|CPUF_DEC|CPUF_LAMS },
     { 0x084E0000,   0xC8FF00C7, 0x0FC,  PAMASK17,   14,     8,  /* S8 */
       CC1|CC2|CC3,  CPUF_STR|CPUF_FP|CPUF_WLK|CPUF_LAMS,     0 },
     { 0x08060000,   0xC8400007, 0x0FC,  PAMASK22,   14,     8,  /* S9 */
@@ -442,7 +445,8 @@ while (reason == 0) {                                   /* loop until stop */
     if (int_hireq < NO_INT) {                           /* interrupt req? */
         uint32 sav_hi, vec, wd, op;
         
-        vec = io_ackn_int (sav_hi = int_hireq);         /* get vector */
+        sav_hi = int_hireq;                             /* save level */
+        vec = io_ackn_int (int_hireq);                  /* get vector */
         if (vec == 0) {                                 /* illegal vector? */
             reason = STOP_ILLVEC;                       /* something wrong */
             break;
@@ -478,7 +482,8 @@ while (reason == 0) {                                   /* loop until stop */
         if (PSW_QRX9 && (PC & PSW1_XA))                 /* S9 real ext && ext? */
             rpc = (PSW2 & PSW2_EA) | (PC & ~PSW1_XA);   /* 22b phys address */
         else rpc = PC;                                  /* standard 17b PC */
-        PC = cpu_add_PC (old_PC = PC, 1);               /* increment PC */
+        old_PC = PC;                                    /* save PC */
+        PC = cpu_add_PC (PC, 1);                        /* increment PC */
         if (((tr = ReadW (rpc << 2, &ir, VI)) != 0) ||  /* fetch inst, err? */
             ((tr = cpu_one_inst (rpc, ir)) != 0)) {     /* exec inst, error? */
             if (tr & TR_FL) {                           /* trap? */
diff --git a/sigma/sigma_defs.h b/sigma/sigma_defs.h
index 362616a2..db50f14b 100644
--- a/sigma/sigma_defs.h
+++ b/sigma/sigma_defs.h
@@ -97,10 +97,11 @@
 #define CPU_V_S5        0
 #define CPU_V_S6        1
 #define CPU_V_S7        2
-#define CPU_V_S8        3                               /* not supported */
-#define CPU_V_S9        4                               /* not supported */
-#define CPU_V_550       5                               /* not supported */
-#define CPU_V_560       6                               /* not supported */
+#define CPU_V_S7B       3
+#define CPU_V_S8        4                               /* not supported */
+#define CPU_V_S9        5                               /* not supported */
+#define CPU_V_550       6                               /* not supported */
+#define CPU_V_560       7                               /* not supported */
 #define CPU_S5          (1u << CPU_V_S5)
 #define CPU_S6          (1u << CPU_V_S6)
 #define CPU_S7          (1u << CPU_V_S7)
@@ -113,10 +114,10 @@
 #define QCPU_S5         (cpu_model == CPU_V_S5)
 #define QCPU_S9         (cpu_model == CPU_V_S9)
 #define QCPU_5X0        ((1u << cpu_model) & (CPU_550|CPU_560))
-#define QCPU_S567       ((1u << cpu_model) & (CPU_S5|CPU_S6|CPU_S7))
+#define QCPU_S567       ((1u << cpu_model) & (CPU_S5|CPU_S6|CPU_S7|CPU_S7B))
 #define QCPU_S89        ((1u << cpu_model) & (CPU_S8|CPU_S9))
 #define QCPU_S89_5X0    ((1u << cpu_model) & (CPU_S8|CPU_S9|CPU_550|CPU_560))
-#define QCPU_BIGM       ((1u << cpu_model) & (CPU_S9|CPU_550|CPU_560))
+#define QCPU_BIGM       ((1u << cpu_model) & (CPU_S7B|CPU_S9|CPU_550|CPU_560))
 
 #define CPU_MUNIT_SIZE  (1u << 15)                      /* mem unit size */