diff --git a/src/cpu/386_common.c b/src/cpu/386_common.c
index 5b0e1a5c4..2853e3c9a 100644
--- a/src/cpu/386_common.c
+++ b/src/cpu/386_common.c
@@ -1449,26 +1449,44 @@ enter_smm(int in_hlt)
 void
 enter_smm_check(int in_hlt)
 {
-    if ((in_smm == 0) && smi_line) {
-#ifdef ENABLE_386_COMMON_LOG
-        x386_common_log("SMI while not in SMM\n");
-#endif
-        enter_smm(in_hlt);
-    } else if ((in_smm == 1) && smi_line) {
-        /* Mark this so that we don't latch more than one SMI. */
-#ifdef ENABLE_386_COMMON_LOG
-        x386_common_log("SMI while in unlatched SMM\n");
-#endif
-        smi_latched = 1;
-    } else if ((in_smm == 2) && smi_line) {
-        /* Mark this so that we don't latch more than one SMI. */
-#ifdef ENABLE_386_COMMON_LOG
-        x386_common_log("SMI while in latched SMM\n");
-#endif
-    }
+    uint8_t ccr1_check = ((ccr1 & (CCR1_USE_SMI | CCR1_SMAC | CCR1_SM3)) ==
+                          (CCR1_USE_SMI | CCR1_SM3)) && (cyrix.arr[3].size > 0);
+
+    if (smi_line) {
+        if (!is_cxsmm || ccr1_check)  switch (in_smm) {
+            default:
+#ifdef ENABLE_386_COMMON_LOG
+                fatal("SMI while in_smm = %i\n", in_smm);
+                break;
+#endif
+            case 0:
+#ifdef ENABLE_386_COMMON_LOG
+                x386_common_log("SMI while not in SMM\n");
+#endif
+                enter_smm(in_hlt);
+                break;
+            case 1:
+                /* Mark this so that we don't latch more than one SMI. */
+#ifdef ENABLE_386_COMMON_LOG
+                x386_common_log("SMI while in unlatched SMM\n");
+#endif
+                smi_latched = 1;
+                break;
+            case 2:
+#ifdef ENABLE_386_COMMON_LOG
+                x386_common_log("SMI while in latched SMM\n");
+#endif
+                break;
+        }
+#ifdef ENABLE_386_COMMON_LOG
+        else {
+            x386_common_log("SMI while in Cyrix disabled mode\n");
+            x386_common_log("lol\n");
+        }
+#endif
 
-    if (smi_line)
         smi_line = 0;
+    }
 }
 
 void
@@ -2186,6 +2204,12 @@ cpu_fast_off_reset(void)
 void
 smi_raise(void)
 {
+    uint8_t ccr1_check = ((ccr1 & (CCR1_USE_SMI | CCR1_SMAC | CCR1_SM3)) ==
+                          (CCR1_USE_SMI | CCR1_SM3)) && (cyrix.arr[3].size > 0);
+
+    if (is_cxsmm && !ccr1_check)
+        return;
+
     if (is486 && (cpu_fast_off_flags & 0x80000000))
         cpu_fast_off_advance();
 
diff --git a/src/cpu/cpu.c b/src/cpu/cpu.c
index 0c621bf68..41ca6932d 100644
--- a/src/cpu/cpu.c
+++ b/src/cpu/cpu.c
@@ -40,6 +40,7 @@
 #include <86box/nmi.h>
 #include <86box/pic.h>
 #include <86box/pci.h>
+#include <86box/smram.h>
 #include <86box/timer.h>
 #include <86box/gdbstub.h>
 #include <86box/plat_fallthrough.h>
@@ -50,13 +51,6 @@
 #endif /* USE_DYNAREC */
 #include "x87_timings.h"
 
-#define CCR1_USE_SMI  (1 << 1)
-#define CCR1_SMAC     (1 << 2)
-#define CCR1_SM3      (1 << 7)
-
-#define CCR3_SMI_LOCK (1 << 0)
-#define CCR3_NMI_EN   (1 << 1)
-
 enum {
     CPUID_FPU       = (1 << 0),  /* On-chip Floating Point Unit */
     CPUID_VME       = (1 << 1),  /* Virtual 8086 mode extensions */
@@ -289,6 +283,10 @@ uint8_t ccr5;
 uint8_t ccr6;
 uint8_t ccr7;
 
+uint8_t reg_30 = 0x00;
+uint8_t arr[24] = { 0 };
+uint8_t rcr[8] = { 0 };
+
 static int cyrix_addr;
 
 static void    cpu_write(uint16_t addr, uint8_t val, void *priv);
@@ -2627,6 +2625,23 @@ cpu_ven_reset(void)
             msr.amd_efer = (cpu_s->cpu_type >= CPU_K6_2C) ? 2ULL : 0ULL;
             break;
 
+        case CPU_Cx6x86MX:
+            ccr0 = 0x00;
+            ccr1 = 0x00;
+            ccr2 = 0x00;
+            ccr3 = 0x00;
+            ccr4 = 0x80;
+            ccr5 = 0x00;
+            ccr6 = 0x00;
+            memset(arr, 0x00, 24);
+            memset(rcr, 0x00, 3);
+            cyrix.arr[3].base = 0x00;
+            cyrix.arr[3].size = 0; /* Disabled */
+            cyrix.smhr &= ~SMHR_VALID;
+            CPUID = cpu_s->cpuid_model;
+            reg_30 = 0xff;
+            break;
+
         case CPU_PENTIUMPRO:
         case CPU_PENTIUM2:
         case CPU_PENTIUM2D:
@@ -4237,78 +4252,105 @@ cpu_write(uint16_t addr, uint8_t val, UNUSED(void *priv))
             picintc(1 << 13);
         else
             nmi = 0;
-        return;
-    } else if (addr >= 0xf1)
-        return; /* FPU stuff */
-
-    if (!(addr & 1))
+    } else if ((addr < 0xf1) && !(addr & 1))
         cyrix_addr = val;
-    else
-        switch (cyrix_addr) {
-            case 0xc0: /* CCR0 */
-                ccr0 = val;
-                break;
-            case 0xc1: /* CCR1 */
-                if ((ccr3 & CCR3_SMI_LOCK) && !in_smm)
-                    val = (val & ~(CCR1_USE_SMI | CCR1_SMAC | CCR1_SM3)) | (ccr1 & (CCR1_USE_SMI | CCR1_SMAC | CCR1_SM3));
-                ccr1 = val;
-                break;
-            case 0xc2: /* CCR2 */
-                ccr2 = val;
-                break;
-            case 0xc3: /* CCR3 */
-                if ((ccr3 & CCR3_SMI_LOCK) && !in_smm)
-                    val = (val & ~(CCR3_NMI_EN)) | (ccr3 & CCR3_NMI_EN) | CCR3_SMI_LOCK;
-                ccr3 = val;
-                break;
-            case 0xcd:
-                if (!(ccr3 & CCR3_SMI_LOCK) || in_smm) {
-                    cyrix.arr[3].base = (cyrix.arr[3].base & ~0xff000000) | (val << 24);
-                    cyrix.smhr &= ~SMHR_VALID;
-                }
-                break;
-            case 0xce:
-                if (!(ccr3 & CCR3_SMI_LOCK) || in_smm) {
-                    cyrix.arr[3].base = (cyrix.arr[3].base & ~0x00ff0000) | (val << 16);
-                    cyrix.smhr &= ~SMHR_VALID;
-                }
-                break;
-            case 0xcf:
-                if (!(ccr3 & CCR3_SMI_LOCK) || in_smm) {
-                    cyrix.arr[3].base = (cyrix.arr[3].base & ~0x0000f000) | ((val & 0xf0) << 8);
-                    if ((val & 0xf) == 0xf)
-                        cyrix.arr[3].size = 1ULL << 32; /* 4 GB */
-                    else if (val & 0xf)
-                        cyrix.arr[3].size = 2048 << (val & 0xf);
-                    else
-                        cyrix.arr[3].size = 0; /* Disabled */
-                    cyrix.smhr &= ~SMHR_VALID;
-                }
-                break;
+    else if (addr < 0xf1)  switch (cyrix_addr) {
+        default:
+            if (cyrix_addr >= 0xc0)
+                fatal("Writing unimplemented Cyrix register %02X\n", cyrix_addr);
+            break;
 
-            case 0xe8: /* CCR4 */
-                if ((ccr3 & 0xf0) == 0x10) {
-                    ccr4 = val;
-                    if (cpu_s->cpu_type >= CPU_Cx6x86) {
-                        if (val & 0x80)
-                            CPUID = cpu_s->cpuid_model;
-                        else
-                            CPUID = 0;
-                    }
+        case 0x30: /* ???? */
+            reg_30 = val;
+            break;
+
+        case 0xc0: /* CCR0 */
+            ccr0 = val;
+            break;
+        case 0xc1: { /* CCR1 */
+            uint8_t old = ccr1;
+            if ((ccr3 & CCR3_SMI_LOCK) && !in_smm)
+                val = (val & ~(CCR1_USE_SMI | CCR1_SMAC | CCR1_SM3)) | (ccr1 & (CCR1_USE_SMI | CCR1_SMAC | CCR1_SM3));
+            ccr1 = val;
+            if ((old ^ ccr1) & (CCR1_SMAC)) {
+                if (ccr1 & CCR1_SMAC)
+                    smram_backup_all();
+                smram_recalc_all(!(ccr1 & CCR1_SMAC));
+            }
+            break;
+        } case 0xc2: /* CCR2 */
+            ccr2 = val;
+            break;
+        case 0xc3: /* CCR3 */
+            if ((ccr3 & CCR3_SMI_LOCK) && !in_smm)
+                val = (val & ~(CCR3_NMI_EN)) | (ccr3 & CCR3_NMI_EN) | CCR3_SMI_LOCK;
+            ccr3 = val;
+            break;
+
+        case 0xc4 ... 0xcc:
+            if (ccr5 & 0x20)
+                arr[cyrix_addr - 0xc4] = val;
+            break;
+        case 0xcd:
+            if ((ccr5 & 0x20) || (!(ccr3 & CCR3_SMI_LOCK) || in_smm)) {
+                arr[cyrix_addr - 0xc4] = val;
+                cyrix.arr[3].base = (cyrix.arr[3].base & ~0xff000000) | (val << 24);
+                cyrix.smhr &= ~SMHR_VALID;
+            }
+            break;
+        case 0xce:
+            if ((ccr5 & 0x20) || (!(ccr3 & CCR3_SMI_LOCK) || in_smm)) {
+                arr[cyrix_addr - 0xc4] = val;
+                cyrix.arr[3].base = (cyrix.arr[3].base & ~0x00ff0000) | (val << 16);
+                cyrix.smhr &= ~SMHR_VALID;
+            }
+            break;
+        case 0xcf:
+            if ((ccr5 & 0x20) || (!(ccr3 & CCR3_SMI_LOCK) || in_smm)) {
+                arr[cyrix_addr - 0xc4] = val;
+                cyrix.arr[3].base = (cyrix.arr[3].base & ~0x0000f000) | ((val & 0xf0) << 8);
+                if ((val & 0xf) == 0xf)
+                    cyrix.arr[3].size = 1ULL << 32; /* 4 GB */
+                else if (val & 0xf)
+                    cyrix.arr[3].size = 2048 << (val & 0xf);
+                else
+                    cyrix.arr[3].size = 0; /* Disabled */
+                cyrix.smhr &= ~SMHR_VALID;
+            }
+            break;
+        case 0xd0 ... 0xdb:
+            if (((ccr3 & 0xf0) == 0x10) && (ccr5 & 0x20))
+                arr[cyrix_addr - 0xc4] = val;
+            break;
+
+        case 0xdc ... 0xe3:
+            if ((ccr3 & 0xf0) == 0x10)
+                rcr[cyrix_addr - 0xdc] = val;
+            break;
+
+        case 0xe8: /* CCR4 */
+            if ((ccr3 & 0xf0) == 0x10) {
+                ccr4 = val;
+                if (cpu_s->cpu_type >= CPU_Cx6x86) {
+                    if (val & 0x80)
+                        CPUID = cpu_s->cpuid_model;
+                    else
+                        CPUID = 0;
                 }
-                break;
-            case 0xe9: /* CCR5 */
-                if ((ccr3 & 0xf0) == 0x10)
-                    ccr5 = val;
-                break;
-            case 0xea: /* CCR6 */
-                if ((ccr3 & 0xf0) == 0x10)
-                    ccr6 = val;
-                break;
-            case 0xeb: /* CCR7 */
-                ccr7 = val & 5;
-                break;
-        }
+            }
+            break;
+        case 0xe9: /* CCR5 */
+            if ((ccr3 & 0xf0) == 0x10)
+                ccr5 = val;
+            break;
+        case 0xea: /* CCR6 */
+            if ((ccr3 & 0xf0) == 0x10)
+                ccr6 = val;
+            break;
+        case 0xeb: /* CCR7 */
+            ccr7 = val & 5;
+            break;
+    }
 }
 
 static uint8_t
@@ -4319,6 +4361,15 @@ cpu_read(uint16_t addr, UNUSED(void *priv))
     if (addr == 0xf007)
         ret = 0x7f;
     else if ((addr < 0xf0) && (addr & 1))  switch (cyrix_addr) {
+        default:
+            if (cyrix_addr >= 0xc0)
+                fatal("Reading unimplemented Cyrix register %02X\n", cyrix_addr);
+            break;
+
+        case 0x30: /* ???? */
+            ret = reg_30;
+            break;
+
         case 0xc0:
             ret = ccr0;
             break;
@@ -4331,14 +4382,36 @@ cpu_read(uint16_t addr, UNUSED(void *priv))
         case 0xc3:
             ret = ccr3;
             break;
+
+        case 0xc4 ... 0xcc:
+            if (ccr5 & 0x20)
+                ret = arr[cyrix_addr - 0xc4];
+            break;
+        case 0xcd ... 0xcf:
+            if ((ccr5 & 0x20) || (!(ccr3 & CCR3_SMI_LOCK) || in_smm))
+                ret = arr[cyrix_addr - 0xc4];
+            break;
+        case 0xd0 ... 0xdb:
+            if (((ccr3 & 0xf0) == 0x10) && (ccr5 & 0x20))
+                ret = arr[cyrix_addr - 0xc4];
+            break;
+
+        case 0xdc ... 0xe3:
+            if ((ccr3 & 0xf0) == 0x10)
+                ret = rcr[cyrix_addr - 0xdc];
+            break;
+
         case 0xe8:
-            ret = ((ccr3 & 0xf0) == 0x10) ? ccr4 : 0xff;
+            if ((ccr3 & 0xf0) == 0x10)
+                ret = ccr4;
             break;
         case 0xe9:
-            ret = ((ccr3 & 0xf0) == 0x10) ? ccr5 : 0xff;
+            if ((ccr3 & 0xf0) == 0x10)
+                ret = ccr5;
             break;
         case 0xea:
-            ret = ((ccr3 & 0xf0) == 0x10) ? ccr6 : 0xff;
+            if ((ccr3 & 0xf0) == 0x10)
+                ret = ccr6;
             break;
         case 0xeb:
             ret = ccr7;
@@ -4349,11 +4422,8 @@ cpu_read(uint16_t addr, UNUSED(void *priv))
         case 0xff:
             ret = cpu_s->cyrix_id >> 8;
             break;
-
-        default:
-            break;
     }
- 
+
     return ret;
 }
 
diff --git a/src/cpu/cpu.h b/src/cpu/cpu.h
index d58da6998..80097294d 100644
--- a/src/cpu/cpu.h
+++ b/src/cpu/cpu.h
@@ -120,6 +120,13 @@ enum {
 #define CPU_ALTERNATE_XTAL   4
 #define CPU_FIXED_MULTIPLIER 8
 
+#define CCR1_USE_SMI  (1 << 1)
+#define CCR1_SMAC     (1 << 2)
+#define CCR1_SM3      (1 << 7)
+
+#define CCR3_SMI_LOCK (1 << 0)
+#define CCR3_NMI_EN   (1 << 1)
+
 #if (defined __amd64__ || defined _M_X64)
 #    define LOOKUP_INV -1LL
 #else
diff --git a/src/cpu/x86_ops_cyrix.h b/src/cpu/x86_ops_cyrix.h
index ac864cd20..c95d4b038 100644
--- a/src/cpu/x86_ops_cyrix.h
+++ b/src/cpu/x86_ops_cyrix.h
@@ -35,7 +35,13 @@ opSVDC_common(uint32_t fetchdat)
 static int
 opSVDC_a16(uint32_t fetchdat)
 {
-    if (in_smm) {
+    uint8_t ins_check = ((ccr1 & (CCR1_USE_SMI | CCR1_SM3)) ==
+                         (CCR1_USE_SMI | CCR1_SM3)) &&
+                        ((ccr1 & CCR1_SMAC) || in_smm) &&
+                        (cyrix.arr[3].size > 0) &&
+                        (CPL == 0);
+
+    if (ins_check) {
         fetch_ea_16(fetchdat);
         SEG_CHECK_WRITE(cpu_state.ea_seg);
         opSVDC_common(fetchdat);
@@ -47,7 +53,13 @@ opSVDC_a16(uint32_t fetchdat)
 static int
 opSVDC_a32(uint32_t fetchdat)
 {
-    if (in_smm) {
+    uint8_t ins_check = ((ccr1 & (CCR1_USE_SMI | CCR1_SM3)) ==
+                         (CCR1_USE_SMI | CCR1_SM3)) &&
+                        ((ccr1 & CCR1_SMAC) || in_smm) &&
+                        (cyrix.arr[3].size > 0) &&
+                        (CPL == 0);
+
+    if (ins_check) {
         fetch_ea_32(fetchdat);
         SEG_CHECK_WRITE(cpu_state.ea_seg);
         opSVDC_common(fetchdat);
@@ -88,7 +100,13 @@ opRSDC_common(uint32_t fetchdat)
 static int
 opRSDC_a16(uint32_t fetchdat)
 {
-    if (in_smm) {
+    uint8_t ins_check = ((ccr1 & (CCR1_USE_SMI | CCR1_SM3)) ==
+                         (CCR1_USE_SMI | CCR1_SM3)) &&
+                        ((ccr1 & CCR1_SMAC) || in_smm) &&
+                        (cyrix.arr[3].size > 0) &&
+                        (CPL == 0);
+
+    if (ins_check) {
         fetch_ea_16(fetchdat);
         SEG_CHECK_READ(cpu_state.ea_seg);
         opRSDC_common(fetchdat);
@@ -100,7 +118,13 @@ opRSDC_a16(uint32_t fetchdat)
 static int
 opRSDC_a32(uint32_t fetchdat)
 {
-    if (in_smm) {
+    uint8_t ins_check = ((ccr1 & (CCR1_USE_SMI | CCR1_SM3)) ==
+                         (CCR1_USE_SMI | CCR1_SM3)) &&
+                        ((ccr1 & CCR1_SMAC) || in_smm) &&
+                        (cyrix.arr[3].size > 0) &&
+                        (CPL == 0);
+
+    if (ins_check) {
         fetch_ea_32(fetchdat);
         SEG_CHECK_READ(cpu_state.ea_seg);
         opRSDC_common(fetchdat);
@@ -113,7 +137,13 @@ opRSDC_a32(uint32_t fetchdat)
 static int
 opSVLDT_a16(uint32_t fetchdat)
 {
-    if (in_smm) {
+    uint8_t ins_check = ((ccr1 & (CCR1_USE_SMI | CCR1_SM3)) ==
+                         (CCR1_USE_SMI | CCR1_SM3)) &&
+                        ((ccr1 & CCR1_SMAC) || in_smm) &&
+                        (cyrix.arr[3].size > 0) &&
+                        (CPL == 0);
+
+    if (ins_check) {
         fetch_ea_16(fetchdat);
         SEG_CHECK_WRITE(cpu_state.ea_seg);
         cyrix_write_seg_descriptor(easeg + cpu_state.eaaddr, &ldt);
@@ -126,7 +156,13 @@ opSVLDT_a16(uint32_t fetchdat)
 static int
 opSVLDT_a32(uint32_t fetchdat)
 {
-    if (in_smm) {
+    uint8_t ins_check = ((ccr1 & (CCR1_USE_SMI | CCR1_SM3)) ==
+                         (CCR1_USE_SMI | CCR1_SM3)) &&
+                        ((ccr1 & CCR1_SMAC) || in_smm) &&
+                        (cyrix.arr[3].size > 0) &&
+                        (CPL == 0);
+
+    if (ins_check) {
         fetch_ea_32(fetchdat);
         SEG_CHECK_WRITE(cpu_state.ea_seg);
         cyrix_write_seg_descriptor(easeg + cpu_state.eaaddr, &ldt);
@@ -140,7 +176,13 @@ opSVLDT_a32(uint32_t fetchdat)
 static int
 opRSLDT_a16(uint32_t fetchdat)
 {
-    if (in_smm) {
+    uint8_t ins_check = ((ccr1 & (CCR1_USE_SMI | CCR1_SM3)) ==
+                         (CCR1_USE_SMI | CCR1_SM3)) &&
+                        ((ccr1 & CCR1_SMAC) || in_smm) &&
+                        (cyrix.arr[3].size > 0) &&
+                        (CPL == 0);
+
+    if (ins_check) {
         fetch_ea_16(fetchdat);
         SEG_CHECK_READ(cpu_state.ea_seg);
         cyrix_load_seg_descriptor(easeg + cpu_state.eaaddr, &ldt);
@@ -152,7 +194,13 @@ opRSLDT_a16(uint32_t fetchdat)
 static int
 opRSLDT_a32(uint32_t fetchdat)
 {
-    if (in_smm) {
+    uint8_t ins_check = ((ccr1 & (CCR1_USE_SMI | CCR1_SM3)) ==
+                         (CCR1_USE_SMI | CCR1_SM3)) &&
+                        ((ccr1 & CCR1_SMAC) || in_smm) &&
+                        (cyrix.arr[3].size > 0) &&
+                        (CPL == 0);
+
+    if (ins_check) {
         fetch_ea_32(fetchdat);
         SEG_CHECK_READ(cpu_state.ea_seg);
         cyrix_load_seg_descriptor(easeg + cpu_state.eaaddr, &ldt);
@@ -165,7 +213,13 @@ opRSLDT_a32(uint32_t fetchdat)
 static int
 opSVTS_a16(uint32_t fetchdat)
 {
-    if (in_smm) {
+    uint8_t ins_check = ((ccr1 & (CCR1_USE_SMI | CCR1_SM3)) ==
+                         (CCR1_USE_SMI | CCR1_SM3)) &&
+                        ((ccr1 & CCR1_SMAC) || in_smm) &&
+                        (cyrix.arr[3].size > 0) &&
+                        (CPL == 0);
+
+    if (ins_check) {
         fetch_ea_16(fetchdat);
         SEG_CHECK_WRITE(cpu_state.ea_seg);
         cyrix_write_seg_descriptor(easeg + cpu_state.eaaddr, &tr);
@@ -178,7 +232,13 @@ opSVTS_a16(uint32_t fetchdat)
 static int
 opSVTS_a32(uint32_t fetchdat)
 {
-    if (in_smm) {
+    uint8_t ins_check = ((ccr1 & (CCR1_USE_SMI | CCR1_SM3)) ==
+                         (CCR1_USE_SMI | CCR1_SM3)) &&
+                        ((ccr1 & CCR1_SMAC) || in_smm) &&
+                        (cyrix.arr[3].size > 0) &&
+                        (CPL == 0);
+
+    if (ins_check) {
         fetch_ea_32(fetchdat);
         SEG_CHECK_WRITE(cpu_state.ea_seg);
         cyrix_write_seg_descriptor(easeg + cpu_state.eaaddr, &tr);
@@ -192,7 +252,13 @@ opSVTS_a32(uint32_t fetchdat)
 static int
 opRSTS_a16(uint32_t fetchdat)
 {
-    if (in_smm) {
+    uint8_t ins_check = ((ccr1 & (CCR1_USE_SMI | CCR1_SM3)) ==
+                         (CCR1_USE_SMI | CCR1_SM3)) &&
+                        ((ccr1 & CCR1_SMAC) || in_smm) &&
+                        (cyrix.arr[3].size > 0) &&
+                        (CPL == 0);
+
+    if (ins_check) {
         fetch_ea_16(fetchdat);
         SEG_CHECK_WRITE(cpu_state.ea_seg);
         cyrix_write_seg_descriptor(easeg + cpu_state.eaaddr, &tr);
@@ -205,7 +271,13 @@ opRSTS_a16(uint32_t fetchdat)
 static int
 opRSTS_a32(uint32_t fetchdat)
 {
-    if (in_smm) {
+    uint8_t ins_check = ((ccr1 & (CCR1_USE_SMI | CCR1_SM3)) ==
+                         (CCR1_USE_SMI | CCR1_SM3)) &&
+                        ((ccr1 & CCR1_SMAC) || in_smm) &&
+                        (cyrix.arr[3].size > 0) &&
+                        (CPL == 0);
+
+    if (ins_check) {
         fetch_ea_32(fetchdat);
         SEG_CHECK_WRITE(cpu_state.ea_seg);
         cyrix_write_seg_descriptor(easeg + cpu_state.eaaddr, &tr);
@@ -219,9 +291,13 @@ opRSTS_a32(uint32_t fetchdat)
 static int
 opSMINT(UNUSED(uint32_t fetchdat))
 {
+    uint8_t ccr1_check = ((ccr1 & (CCR1_USE_SMI | CCR1_SMAC | CCR1_SM3)) ==
+                          (CCR1_USE_SMI | CCR1_SMAC | CCR1_SM3)) &&
+                          (cyrix.arr[3].size > 0);
+
     if (in_smm)
         fatal("opSMINT\n");
-    else {
+    else if (ccr1_check) {
         is_smint = 1;
         enter_smm(0);
     }
@@ -232,9 +308,26 @@ opSMINT(UNUSED(uint32_t fetchdat))
 static int
 opRDSHR_a16(UNUSED(uint32_t fetchdat))
 {
-    if (in_smm)
-        fatal("opRDSHR_a16\n");
-    else
+    uint8_t ins_check = ((ccr1 & (CCR1_USE_SMI | CCR1_SM3)) ==
+                         (CCR1_USE_SMI | CCR1_SM3)) &&
+                        ((ccr1 & CCR1_SMAC) || in_smm) &&
+                        (cyrix.arr[3].size > 0) &&
+                        (CPL == 0);
+
+    if (ins_check) {
+        fetch_ea_16(fetchdat);
+        if (cpu_mod == 3) {
+            cpu_state.regs[cpu_rm].l = cyrix.smhr;
+            CLOCK_CYCLES(timing_rr);
+            PREFETCH_RUN(timing_rr, 2, rmdat, 0, 0, 0, 0, 0);
+        } else {
+            SEG_CHECK_WRITE(cpu_state.ea_seg);
+            seteal(cyrix.smhr);
+            CLOCK_CYCLES(is486 ? 1 : 2);
+            PREFETCH_RUN(2, 2, rmdat, 0, 0, 0, 1, 0);
+        }
+        return cpu_state.abrt;
+    } else
         x86illegal();
 
     return 1;
@@ -242,30 +335,91 @@ opRDSHR_a16(UNUSED(uint32_t fetchdat))
 static int
 opRDSHR_a32(UNUSED(uint32_t fetchdat))
 {
-    if (in_smm)
-        fatal("opRDSHR_a32\n");
-    else
+    uint8_t ins_check = ((ccr1 & (CCR1_USE_SMI | CCR1_SM3)) ==
+                         (CCR1_USE_SMI | CCR1_SM3)) &&
+                        ((ccr1 & CCR1_SMAC) || in_smm) &&
+                        (cyrix.arr[3].size > 0) &&
+                        (CPL == 0);
+
+    if (ins_check) {
+        fetch_ea_32(fetchdat);
+        if (cpu_mod == 3) {
+            cpu_state.regs[cpu_rm].l = cyrix.smhr;
+            CLOCK_CYCLES(timing_rr);
+            PREFETCH_RUN(timing_rr, 2, rmdat, 0, 0, 0, 0, 1);
+        } else {
+            SEG_CHECK_WRITE(cpu_state.ea_seg);
+            seteal(cyrix.smhr);
+            CLOCK_CYCLES(is486 ? 1 : 2);
+            PREFETCH_RUN(2, 2, rmdat, 0, 0, 0, 1, 1);
+        }
+        return cpu_state.abrt;
+    } else
         x86illegal();
 
     return 1;
 }
 
 static int
-opWRSHR_a16(UNUSED(uint32_t fetchdat))
+opWRSHR_a16(uint32_t fetchdat)
 {
-    if (in_smm)
-        fatal("opWRSHR_a16\n");
-    else
+    uint8_t ins_check = ((ccr1 & (CCR1_USE_SMI | CCR1_SM3)) ==
+                         (CCR1_USE_SMI | CCR1_SM3)) &&
+                        ((ccr1 & CCR1_SMAC) || in_smm) &&
+                        (cyrix.arr[3].size > 0) &&
+                        (CPL == 0);
+
+    if (ins_check) {
+        fetch_ea_16(fetchdat);
+        if (cpu_mod == 3) {
+            cyrix.smhr = cpu_state.regs[cpu_rm].l;
+            CLOCK_CYCLES(timing_rr);
+            PREFETCH_RUN(timing_rr, 2, rmdat, 0, 0, 0, 0, 0);
+        } else {
+            uint32_t temp;
+            SEG_CHECK_READ(cpu_state.ea_seg);
+            CHECK_READ(cpu_state.ea_seg, cpu_state.eaaddr, cpu_state.eaaddr + 3);
+            temp = geteal();
+            if (cpu_state.abrt)
+                return 1;
+            cyrix.smhr = temp;
+            CLOCK_CYCLES(is486 ? 1 : 4);
+            PREFETCH_RUN(4, 2, rmdat, 0, 1, 0, 0, 0);
+        }
+        return 0;
+    } else
         x86illegal();
 
     return 1;
 }
 static int
-opWRSHR_a32(UNUSED(uint32_t fetchdat))
+opWRSHR_a32(uint32_t fetchdat)
 {
-    if (in_smm)
-        fatal("opWRSHR_a32\n");
-    else
+    uint8_t ins_check = ((ccr1 & (CCR1_USE_SMI | CCR1_SM3)) ==
+                         (CCR1_USE_SMI | CCR1_SM3)) &&
+                        ((ccr1 & CCR1_SMAC) || in_smm) &&
+                        (cyrix.arr[3].size > 0) &&
+                        (CPL == 0);
+
+    if (ins_check) {
+        fetch_ea_32(fetchdat);
+        if (cpu_mod == 3) {
+            cyrix.smhr = cpu_state.regs[cpu_rm].l;
+            CLOCK_CYCLES(timing_rr);
+            PREFETCH_RUN(timing_rr, 2, rmdat, 0, 0, 0, 0, 1);
+        } else {
+            uint32_t temp;
+            SEG_CHECK_READ(cpu_state.ea_seg);
+            CHECK_READ(cpu_state.ea_seg, cpu_state.eaaddr, cpu_state.eaaddr + 3);
+            temp = geteal();
+            if (cpu_state.abrt)
+                return 1;
+            cyrix.smhr = temp;
+            CLOCK_CYCLES(is486 ? 1 : 4);
+            PREFETCH_RUN(4, 2, rmdat, 0, 1, 0, 0, 1);
+        }
+        return 0;
+    } else
         x86illegal();
 
     return 1;