diff --git a/src/x87.c b/src/x87.c
index 25ce726..625e56e 100644
--- a/src/x87.c
+++ b/src/x87.c
@@ -19,6 +19,11 @@
 #include "x87.h"
 #include "386_common.h"
 
+#define X87_TAG_VALID   0
+#define X87_TAG_ZERO    1
+#define X87_TAG_INVALID 2
+#define X87_TAG_EMPTY   3
+
 uint16_t x87_gettag()
 {
         uint16_t ret = 0;
@@ -26,10 +31,14 @@ uint16_t x87_gettag()
         
         for (c = 0; c < 8; c++)
         {
-                if (cpu_state.tag[c] & TAG_UINT64)
+                if (cpu_state.tag[c] == TAG_EMPTY)
+                        ret |= X87_TAG_EMPTY << (c * 2);
+                else if (cpu_state.tag[c] & TAG_UINT64)
                         ret |= 2 << (c*2);
+                else if (cpu_state.ST[c] == 0.0)
+                        ret |= X87_TAG_ZERO << (c * 2);
                 else
-                        ret |= (cpu_state.tag[c] << (c*2));
+                        ret |= X87_TAG_VALID << (c * 2);
         }
 
         return ret;
@@ -37,14 +46,19 @@ uint16_t x87_gettag()
 
 void x87_settag(uint16_t new_tag)
 {
-        cpu_state.tag[0] = new_tag & 3;
-        cpu_state.tag[1] = (new_tag >> 2) & 3;
-        cpu_state.tag[2] = (new_tag >> 4) & 3;
-        cpu_state.tag[3] = (new_tag >> 6) & 3;
-        cpu_state.tag[4] = (new_tag >> 8) & 3;
-        cpu_state.tag[5] = (new_tag >> 10) & 3;
-        cpu_state.tag[6] = (new_tag >> 12) & 3;
-        cpu_state.tag[7] = (new_tag >> 14) & 3;
+        int c;
+        
+        for (c = 0; c < 8; c++)
+        {
+                int tag = (new_tag >> (c * 2)) & 3;
+                
+                if (tag == X87_TAG_EMPTY)
+                        cpu_state.tag[c] = TAG_EMPTY;
+                else if (tag == 2)
+                        cpu_state.tag[c] = TAG_VALID | TAG_UINT64;
+                else
+                        cpu_state.tag[c] = TAG_VALID;
+        }
 }
 
 void x87_dumpregs()
diff --git a/src/x87.h b/src/x87.h
index 790b6eb..cd4ccbb 100644
--- a/src/x87.h
+++ b/src/x87.h
@@ -10,7 +10,7 @@ static inline void x87_set_mmx()
 
 static inline void x87_emms()
 {
-        *(uint64_t *)cpu_state.tag = 0x0303030303030303ll;
+        *(uint64_t *)cpu_state.tag = 0;
         cpu_state.ismmx = 0;
 }
 
@@ -19,5 +19,8 @@ void x87_settag(uint16_t new_tag);
 void x87_dumpregs();
 void x87_reset();
 
+#define TAG_EMPTY  0
+#define TAG_VALID  (1 << 0)
 /*Hack for FPU copy. If set then MM[].q contains the 64-bit integer loaded by FILD*/
-#define TAG_UINT64 (1 << 2)
+#define TAG_UINT64 (1 << 7)
+
diff --git a/src/x87_ops.h b/src/x87_ops.h
index dc15866..3756c19 100644
--- a/src/x87_ops.h
+++ b/src/x87_ops.h
@@ -40,7 +40,7 @@ static inline void x87_push(double i)
 {
         cpu_state.TOP=(cpu_state.TOP-1)&7;
         cpu_state.ST[cpu_state.TOP] = i;
-        cpu_state.tag[cpu_state.TOP&7] = (i == 0.0) ? 1 : 0;
+        cpu_state.tag[cpu_state.TOP&7] = TAG_VALID;
 }
 
 static inline void x87_push_u64(uint64_t i)
@@ -55,13 +55,13 @@ static inline void x87_push_u64(uint64_t i)
 
         cpu_state.TOP=(cpu_state.TOP-1)&7;
         cpu_state.ST[cpu_state.TOP] = td.d;
-        cpu_state.tag[cpu_state.TOP&7] = (td.d == 0.0) ? 1 : 0;
+        cpu_state.tag[cpu_state.TOP&7] = TAG_VALID;
 }
 
 static inline double x87_pop()
 {
         double t = cpu_state.ST[cpu_state.TOP];
-        cpu_state.tag[cpu_state.TOP&7] = 3;
+        cpu_state.tag[cpu_state.TOP&7] = TAG_EMPTY;
         cpu_state.TOP=(cpu_state.TOP+1)&7;
         return t;
 }
@@ -186,13 +186,15 @@ static inline void x87_ld_frstor(int reg)
         cpu_state.MM[reg].q = readmemq(easeg, cpu_state.eaaddr);
         cpu_state.MM_w4[reg] = readmemw(easeg, cpu_state.eaaddr + 8);
 
-        if (cpu_state.MM_w4[reg] == 0x5555 && cpu_state.tag[reg] == 2)
+        if ((cpu_state.MM_w4[reg] == 0x5555) && (cpu_state.tag[reg] & TAG_UINT64))
         {
-                cpu_state.tag[reg] = TAG_UINT64;
                 cpu_state.ST[reg] = (double)cpu_state.MM[reg].q;
         }
         else
+        {
+                cpu_state.tag[reg] = TAG_VALID;
                 cpu_state.ST[reg] = x87_ld80();
+        }
 }
 
 static inline void x87_ldmmx(MMX_REG *r, uint16_t *w4)
diff --git a/src/x87_ops_arith.h b/src/x87_ops_arith.h
index 45077c7..4561c82 100644
--- a/src/x87_ops_arith.h
+++ b/src/x87_ops_arith.h
@@ -11,7 +11,7 @@ static int opFADD ## name ## _a ## a_size(uint32_t fetchdat)    \
         ST(0) += use_var;                                       \
         if ((cpu_state.npxc >> 10) & 3)                                   \
                 fesetround(FE_TONEAREST);                       \
-        cpu_state.tag[cpu_state.TOP] &= ~TAG_UINT64;                                \
+        cpu_state.tag[cpu_state.TOP] = TAG_VALID;               \
         CLOCK_CYCLES(8);                                        \
         return 0;                                               \
 }                                                               \
@@ -48,7 +48,7 @@ static int opFDIV ## name ## _a ## a_size(uint32_t fetchdat)    \
         SEG_CHECK_READ(cpu_state.ea_seg);                       \
         load_var = get(); if (cpu_state.abrt) return 1;                   \
         x87_div(ST(0), ST(0), use_var);                         \
-        cpu_state.tag[cpu_state.TOP] &= ~TAG_UINT64;                                \
+        cpu_state.tag[cpu_state.TOP] = TAG_VALID;               \
         CLOCK_CYCLES(73);                                       \
         return 0;                                               \
 }                                                               \
@@ -60,7 +60,7 @@ static int opFDIVR ## name ## _a ## a_size(uint32_t fetchdat)   \
         SEG_CHECK_READ(cpu_state.ea_seg);                       \
         load_var = get(); if (cpu_state.abrt) return 1;                   \
         x87_div(ST(0), use_var, ST(0));                         \
-        cpu_state.tag[cpu_state.TOP] &= ~TAG_UINT64;                                \
+        cpu_state.tag[cpu_state.TOP] = TAG_VALID;               \
         CLOCK_CYCLES(73);                                       \
         return 0;                                               \
 }                                                               \
@@ -72,7 +72,7 @@ static int opFMUL ## name ## _a ## a_size(uint32_t fetchdat)    \
         SEG_CHECK_READ(cpu_state.ea_seg);                       \
         load_var = get(); if (cpu_state.abrt) return 1;                   \
         ST(0) *= use_var;                                       \
-        cpu_state.tag[cpu_state.TOP] &= ~TAG_UINT64;                                \
+        cpu_state.tag[cpu_state.TOP] = TAG_VALID;               \
         CLOCK_CYCLES(11);                                       \
         return 0;                                               \
 }                                                               \
@@ -84,7 +84,7 @@ static int opFSUB ## name ## _a ## a_size(uint32_t fetchdat)    \
         SEG_CHECK_READ(cpu_state.ea_seg);                       \
         load_var = get(); if (cpu_state.abrt) return 1;                   \
         ST(0) -= use_var;                                       \
-        cpu_state.tag[cpu_state.TOP] &= ~TAG_UINT64;                                \
+        cpu_state.tag[cpu_state.TOP] = TAG_VALID;               \
         CLOCK_CYCLES(8);                                        \
         return 0;                                               \
 }                                                               \
@@ -96,7 +96,7 @@ static int opFSUBR ## name ## _a ## a_size(uint32_t fetchdat)   \
         SEG_CHECK_READ(cpu_state.ea_seg);                       \
         load_var = get(); if (cpu_state.abrt) return 1;                   \
         ST(0) = use_var - ST(0);                                \
-        cpu_state.tag[cpu_state.TOP] &= ~TAG_UINT64;                                \
+        cpu_state.tag[cpu_state.TOP] = TAG_VALID;               \
         CLOCK_CYCLES(8);                                        \
         return 0;                                               \
 }
@@ -121,7 +121,7 @@ static int opFADD(uint32_t fetchdat)
         cpu_state.pc++;
         if (fplog) pclog("FADD\n");
         ST(0) = ST(0) + ST(fetchdat & 7);
-        cpu_state.tag[cpu_state.TOP] &= ~TAG_UINT64;
+        cpu_state.tag[cpu_state.TOP] = TAG_VALID;
         CLOCK_CYCLES(8);
         return 0;
 }
@@ -131,7 +131,7 @@ static int opFADDr(uint32_t fetchdat)
         cpu_state.pc++;
         if (fplog) pclog("FADD\n");
         ST(fetchdat & 7) = ST(fetchdat & 7) + ST(0);
-        cpu_state.tag[(cpu_state.TOP + fetchdat) & 7] &= ~TAG_UINT64;
+        cpu_state.tag[(cpu_state.TOP + fetchdat) & 7] = TAG_VALID;
         CLOCK_CYCLES(8);
         return 0;
 }
@@ -141,7 +141,7 @@ static int opFADDP(uint32_t fetchdat)
         cpu_state.pc++;
         if (fplog) pclog("FADDP\n");
         ST(fetchdat & 7) = ST(fetchdat & 7) + ST(0);
-        cpu_state.tag[(cpu_state.TOP + fetchdat) & 7] &= ~TAG_UINT64;
+        cpu_state.tag[(cpu_state.TOP + fetchdat) & 7] = TAG_VALID;
         x87_pop();
         CLOCK_CYCLES(8);
         return 0;
@@ -232,7 +232,7 @@ static int opFDIV(uint32_t fetchdat)
         cpu_state.pc++;
         if (fplog) pclog("FDIV\n");
         x87_div(ST(0), ST(0), ST(fetchdat & 7));
-        cpu_state.tag[cpu_state.TOP] &= ~TAG_UINT64;
+        cpu_state.tag[cpu_state.TOP] = TAG_VALID;
         CLOCK_CYCLES(73);
         return 0;
 }
@@ -242,7 +242,7 @@ static int opFDIVr(uint32_t fetchdat)
         cpu_state.pc++;
         if (fplog) pclog("FDIV\n");
         x87_div(ST(fetchdat & 7), ST(fetchdat & 7), ST(0));
-        cpu_state.tag[(cpu_state.TOP + fetchdat) & 7] &= ~TAG_UINT64;
+        cpu_state.tag[(cpu_state.TOP + fetchdat) & 7] = TAG_VALID;
         CLOCK_CYCLES(73);
         return 0;
 }
@@ -252,7 +252,7 @@ static int opFDIVP(uint32_t fetchdat)
         cpu_state.pc++;
         if (fplog) pclog("FDIVP\n");
         x87_div(ST(fetchdat & 7), ST(fetchdat & 7), ST(0));
-        cpu_state.tag[(cpu_state.TOP + fetchdat) & 7] &= ~TAG_UINT64;
+        cpu_state.tag[(cpu_state.TOP + fetchdat) & 7] = TAG_VALID;
         x87_pop();
         CLOCK_CYCLES(73);
         return 0;
@@ -264,7 +264,7 @@ static int opFDIVR(uint32_t fetchdat)
         cpu_state.pc++;
         if (fplog) pclog("FDIVR\n");
         x87_div(ST(0), ST(fetchdat&7), ST(0));
-        cpu_state.tag[cpu_state.TOP] &= ~TAG_UINT64;
+        cpu_state.tag[cpu_state.TOP] = TAG_VALID;
         CLOCK_CYCLES(73);
         return 0;
 }
@@ -274,7 +274,7 @@ static int opFDIVRr(uint32_t fetchdat)
         cpu_state.pc++;
         if (fplog) pclog("FDIVR\n");
         x87_div(ST(fetchdat & 7), ST(0), ST(fetchdat & 7));
-        cpu_state.tag[(cpu_state.TOP + fetchdat) & 7] &= ~TAG_UINT64;
+        cpu_state.tag[(cpu_state.TOP + fetchdat) & 7] = TAG_VALID;
         CLOCK_CYCLES(73);
         return 0;
 }
@@ -284,7 +284,7 @@ static int opFDIVRP(uint32_t fetchdat)
         cpu_state.pc++;
         if (fplog) pclog("FDIVR\n");
         x87_div(ST(fetchdat & 7), ST(0), ST(fetchdat & 7));
-        cpu_state.tag[(cpu_state.TOP + fetchdat) & 7] &= ~TAG_UINT64;
+        cpu_state.tag[(cpu_state.TOP + fetchdat) & 7] = TAG_VALID;
         x87_pop();
         CLOCK_CYCLES(73);
         return 0;
@@ -296,7 +296,7 @@ static int opFMUL(uint32_t fetchdat)
         cpu_state.pc++;
         if (fplog) pclog("FMUL\n");
         ST(0) = ST(0) * ST(fetchdat & 7);
-        cpu_state.tag[cpu_state.TOP] &= ~TAG_UINT64;
+        cpu_state.tag[cpu_state.TOP] = TAG_VALID;
         CLOCK_CYCLES(16);
         return 0;
 }
@@ -306,7 +306,7 @@ static int opFMULr(uint32_t fetchdat)
         cpu_state.pc++;
         if (fplog) pclog("FMUL\n");
         ST(fetchdat & 7) = ST(0) * ST(fetchdat & 7);
-        cpu_state.tag[(cpu_state.TOP + fetchdat) & 7] &= ~TAG_UINT64;
+        cpu_state.tag[(cpu_state.TOP + fetchdat) & 7] = TAG_VALID;
         CLOCK_CYCLES(16);
         return 0;
 }
@@ -316,7 +316,7 @@ static int opFMULP(uint32_t fetchdat)
         cpu_state.pc++;
         if (fplog) pclog("FMULP\n");
         ST(fetchdat & 7) = ST(0) * ST(fetchdat & 7);
-        cpu_state.tag[(cpu_state.TOP + fetchdat) & 7] &= ~TAG_UINT64;
+        cpu_state.tag[(cpu_state.TOP + fetchdat) & 7] = TAG_VALID;
         x87_pop();
         CLOCK_CYCLES(16);
         return 0;
@@ -328,7 +328,7 @@ static int opFSUB(uint32_t fetchdat)
         cpu_state.pc++;
         if (fplog) pclog("FSUB\n");
         ST(0) = ST(0) - ST(fetchdat & 7);
-        cpu_state.tag[cpu_state.TOP] &= ~TAG_UINT64;
+        cpu_state.tag[cpu_state.TOP] = TAG_VALID;
         CLOCK_CYCLES(8);
         return 0;
 }
@@ -338,7 +338,7 @@ static int opFSUBr(uint32_t fetchdat)
         cpu_state.pc++;
         if (fplog) pclog("FSUB\n");
         ST(fetchdat & 7) = ST(fetchdat & 7) - ST(0);
-        cpu_state.tag[(cpu_state.TOP + fetchdat) & 7] &= ~TAG_UINT64;
+        cpu_state.tag[(cpu_state.TOP + fetchdat) & 7] = TAG_VALID;
         CLOCK_CYCLES(8);
         return 0;
 }
@@ -348,7 +348,7 @@ static int opFSUBP(uint32_t fetchdat)
         cpu_state.pc++;
         if (fplog) pclog("FSUBP\n");
         ST(fetchdat & 7) = ST(fetchdat & 7) - ST(0);
-        cpu_state.tag[(cpu_state.TOP + fetchdat) & 7] &= ~TAG_UINT64;
+        cpu_state.tag[(cpu_state.TOP + fetchdat) & 7] = TAG_VALID;
         x87_pop();
         CLOCK_CYCLES(8);
         return 0;
@@ -360,7 +360,7 @@ static int opFSUBR(uint32_t fetchdat)
         cpu_state.pc++;
         if (fplog) pclog("FSUBR\n");
         ST(0) = ST(fetchdat & 7) - ST(0);
-        cpu_state.tag[cpu_state.TOP] &= ~TAG_UINT64;
+        cpu_state.tag[cpu_state.TOP] = TAG_VALID;
         CLOCK_CYCLES(8);
         return 0;
 }
@@ -370,7 +370,7 @@ static int opFSUBRr(uint32_t fetchdat)
         cpu_state.pc++;
         if (fplog) pclog("FSUBR\n");
         ST(fetchdat & 7) = ST(0) - ST(fetchdat & 7);
-        cpu_state.tag[(cpu_state.TOP + fetchdat) & 7] &= ~TAG_UINT64;
+        cpu_state.tag[(cpu_state.TOP + fetchdat) & 7] = TAG_VALID;
         CLOCK_CYCLES(8);
         return 0;
 }
@@ -380,7 +380,7 @@ static int opFSUBRP(uint32_t fetchdat)
         cpu_state.pc++;
         if (fplog) pclog("FSUBRP\n");
         ST(fetchdat & 7) = ST(0) - ST(fetchdat & 7);
-        cpu_state.tag[(cpu_state.TOP + fetchdat) & 7] &= ~TAG_UINT64;
+        cpu_state.tag[(cpu_state.TOP + fetchdat) & 7] = TAG_VALID;
         x87_pop();
         CLOCK_CYCLES(8);
         return 0;
diff --git a/src/x87_ops_loadstore.h b/src/x87_ops_loadstore.h
index bf9fc1f..7a0b938 100644
--- a/src/x87_ops_loadstore.h
+++ b/src/x87_ops_loadstore.h
@@ -96,7 +96,7 @@ static int opFILDiq_a16(uint32_t fetchdat)
         if (fplog) pclog("  %f  %08X %08X\n", (double)temp64, readmeml(easeg,cpu_state.eaaddr), readmeml(easeg,cpu_state.eaaddr+4));
         x87_push((double)temp64);
         cpu_state.MM[cpu_state.TOP].q = temp64;
-        cpu_state.tag[cpu_state.TOP] |= TAG_UINT64;
+        cpu_state.tag[cpu_state.TOP] = TAG_VALID | TAG_UINT64;
 
         CLOCK_CYCLES(10);
         return 0;
@@ -112,7 +112,7 @@ static int opFILDiq_a32(uint32_t fetchdat)
         if (fplog) pclog("  %f  %08X %08X\n", (double)temp64, readmeml(easeg,cpu_state.eaaddr), readmeml(easeg,cpu_state.eaaddr+4));
         x87_push((double)temp64);
         cpu_state.MM[cpu_state.TOP].q = temp64;
-        cpu_state.tag[cpu_state.TOP] |= TAG_UINT64;
+        cpu_state.tag[cpu_state.TOP] = TAG_VALID | TAG_UINT64;
 
         CLOCK_CYCLES(10);
         return 0;
diff --git a/src/x87_ops_misc.h b/src/x87_ops_misc.h
index 5f21a99..34a28d0 100644
--- a/src/x87_ops_misc.h
+++ b/src/x87_ops_misc.h
@@ -34,7 +34,7 @@ static int opFINIT(uint32_t fetchdat)
         cpu_state.npxc = 0x37F;
         cpu_state.new_npxc = (cpu_state.old_npxc & ~0xc00);
         cpu_state.npxs = 0;
-        *(uint64_t *)cpu_state.tag = 0x0303030303030303ll;
+        *(uint64_t *)cpu_state.tag = 0;
         cpu_state.TOP = 0;
         cpu_state.ismmx = 0;
         CLOCK_CYCLES(17);
@@ -47,7 +47,7 @@ static int opFFREE(uint32_t fetchdat)
         FP_ENTER();
         cpu_state.pc++;
         if (fplog) pclog("FFREE\n");
-        cpu_state.tag[(cpu_state.TOP + fetchdat) & 7] = 3;
+        cpu_state.tag[(cpu_state.TOP + fetchdat) & 7] = TAG_EMPTY;
         CLOCK_CYCLES(3);
         return 0;
 }
@@ -278,7 +278,7 @@ static int FSAVE()
         cpu_state.npxc = 0x37F;
         cpu_state.new_npxc = (cpu_state.old_npxc & ~0xc00);
         cpu_state.npxs = 0;
-        *(uint64_t *)cpu_state.tag = 0x0303030303030303ll;
+        *(uint64_t *)cpu_state.tag = 0;
         cpu_state.TOP = 0;
         cpu_state.ismmx = 0;
 
@@ -369,7 +369,7 @@ static int opFCHS(uint32_t fetchdat)
         cpu_state.pc++;
         if (fplog) pclog("FCHS\n");
         ST(0) = -ST(0);
-        cpu_state.tag[cpu_state.TOP] &= ~TAG_UINT64;
+        cpu_state.tag[cpu_state.TOP] = TAG_VALID;
         CLOCK_CYCLES(6);
         return 0;
 }
@@ -380,7 +380,7 @@ static int opFABS(uint32_t fetchdat)
         cpu_state.pc++;
         if (fplog) pclog("FABS %f\n", ST(0));
         ST(0) = fabs(ST(0));
-        cpu_state.tag[cpu_state.TOP] &= ~TAG_UINT64;
+        cpu_state.tag[cpu_state.TOP] = TAG_VALID;
         CLOCK_CYCLES(3);
         return 0;
 }
@@ -403,7 +403,7 @@ static int opFXAM(uint32_t fetchdat)
         cpu_state.pc++;
         if (fplog) pclog("FXAM %i %f\n", cpu_state.tag[cpu_state.TOP&7], ST(0));
         cpu_state.npxs &= ~(C0|C1|C2|C3);
-        if (cpu_state.tag[cpu_state.TOP&7] == 3)   cpu_state.npxs |= (C0|C3);
+        if (cpu_state.tag[cpu_state.TOP&7] == TAG_EMPTY)   cpu_state.npxs |= (C0|C3);
         else if (ST(0) == 0.0) cpu_state.npxs |= C3;
         else                   cpu_state.npxs |= C2;
         if (ST(0) < 0.0)       cpu_state.npxs |= C1;
@@ -477,7 +477,7 @@ static int opFLDZ(uint32_t fetchdat)
         cpu_state.pc++;
         if (fplog) pclog("FLDZ\n");
         x87_push(0.0);
-        cpu_state.tag[cpu_state.TOP&7] = 1;
+        cpu_state.tag[cpu_state.TOP&7] = TAG_VALID;
         CLOCK_CYCLES(4);
         return 0;
 }
@@ -488,7 +488,7 @@ static int opF2XM1(uint32_t fetchdat)
         cpu_state.pc++;
         if (fplog) pclog("F2XM1\n");
         ST(0) = pow(2.0, ST(0)) - 1.0;
-        cpu_state.tag[cpu_state.TOP] &= ~TAG_UINT64;
+        cpu_state.tag[cpu_state.TOP] = TAG_VALID;
         CLOCK_CYCLES(200);
         return 0;
 }
@@ -499,7 +499,7 @@ static int opFYL2X(uint32_t fetchdat)
         cpu_state.pc++;
         if (fplog) pclog("FYL2X\n");
         ST(1) = ST(1) * (log(ST(0)) / log(2.0));
-        cpu_state.tag[(cpu_state.TOP + 1) & 7] &= ~TAG_UINT64;
+        cpu_state.tag[(cpu_state.TOP + 1) & 7] = TAG_VALID;
         x87_pop();
         CLOCK_CYCLES(250);
         return 0;
@@ -511,7 +511,7 @@ static int opFYL2XP1(uint32_t fetchdat)
         cpu_state.pc++;
         if (fplog) pclog("FYL2XP1\n");
         ST(1) = ST(1) * (log(ST(0)+1.0) / log(2.0));
-        cpu_state.tag[(cpu_state.TOP + 1) & 7] &= ~TAG_UINT64;
+        cpu_state.tag[(cpu_state.TOP + 1) & 7] = TAG_VALID;
         x87_pop();
         CLOCK_CYCLES(250);
         return 0;
@@ -523,7 +523,7 @@ static int opFPTAN(uint32_t fetchdat)
         cpu_state.pc++;
         if (fplog) pclog("FPTAN\n");
         ST(0) = tan(ST(0));
-        cpu_state.tag[cpu_state.TOP] &= ~TAG_UINT64;
+        cpu_state.tag[cpu_state.TOP] = TAG_VALID;
         x87_push(1.0);
         cpu_state.npxs &= ~C2;
         CLOCK_CYCLES(235);
@@ -536,7 +536,7 @@ static int opFPATAN(uint32_t fetchdat)
         cpu_state.pc++;
         if (fplog) pclog("FPATAN\n");
         ST(1) = atan2(ST(1), ST(0));
-        cpu_state.tag[(cpu_state.TOP + 1) & 7] &= ~TAG_UINT64;
+        cpu_state.tag[(cpu_state.TOP + 1) & 7] = TAG_VALID;
         x87_pop();
         CLOCK_CYCLES(250);
         return 0;
@@ -570,7 +570,7 @@ static int opFPREM(uint32_t fetchdat)
         if (fplog) pclog("FPREM %f %f  ", ST(0), ST(1));
         temp64 = (int64_t)(ST(0) / ST(1));
         ST(0) = ST(0) - (ST(1) * (double)temp64);
-        cpu_state.tag[cpu_state.TOP] &= ~TAG_UINT64;
+        cpu_state.tag[cpu_state.TOP] = TAG_VALID;
         if (fplog) pclog("%f\n", ST(0));
         cpu_state.npxs &= ~(C0|C1|C2|C3);
         if (temp64 & 4) cpu_state.npxs|=C0;
@@ -587,7 +587,7 @@ static int opFPREM1(uint32_t fetchdat)
         if (fplog) pclog("FPREM1 %f %f  ", ST(0), ST(1));
         temp64 = (int64_t)(ST(0) / ST(1));
         ST(0) = ST(0) - (ST(1) * (double)temp64);
-        cpu_state.tag[cpu_state.TOP] &= ~TAG_UINT64;
+        cpu_state.tag[cpu_state.TOP] = TAG_VALID;
         if (fplog) pclog("%f\n", ST(0));
         cpu_state.npxs &= ~(C0|C1|C2|C3);
         if (temp64 & 4) cpu_state.npxs|=C0;
@@ -603,7 +603,7 @@ static int opFSQRT(uint32_t fetchdat)
         cpu_state.pc++;
         if (fplog) pclog("FSQRT\n");
         ST(0) = sqrt(ST(0));
-        cpu_state.tag[cpu_state.TOP] &= ~TAG_UINT64;
+        cpu_state.tag[cpu_state.TOP] = TAG_VALID;
         CLOCK_CYCLES(83);
         return 0;
 }
@@ -616,7 +616,7 @@ static int opFSINCOS(uint32_t fetchdat)
         if (fplog) pclog("FSINCOS\n");
         td = ST(0);
         ST(0) = sin(td);
-        cpu_state.tag[cpu_state.TOP] &= ~TAG_UINT64;
+        cpu_state.tag[cpu_state.TOP] = TAG_VALID;
         x87_push(cos(td));
         cpu_state.npxs &= ~C2;
         CLOCK_CYCLES(330);
@@ -629,7 +629,7 @@ static int opFRNDINT(uint32_t fetchdat)
         cpu_state.pc++;
         if (fplog) pclog("FRNDINT %g ", ST(0));
         ST(0) = (double)x87_fround(ST(0));
-        cpu_state.tag[cpu_state.TOP] &= ~TAG_UINT64;
+        cpu_state.tag[cpu_state.TOP] = TAG_VALID;
         if (fplog) pclog("%g\n", ST(0));
         CLOCK_CYCLES(21);
         return 0;
@@ -643,7 +643,7 @@ static int opFSCALE(uint32_t fetchdat)
         if (fplog) pclog("FSCALE\n");
         temp64 = (int64_t)ST(1);
         ST(0) = ST(0) * pow(2.0, (double)temp64);
-        cpu_state.tag[cpu_state.TOP] &= ~TAG_UINT64;
+        cpu_state.tag[cpu_state.TOP] = TAG_VALID;
         CLOCK_CYCLES(30);
         return 0;
 }
@@ -654,7 +654,7 @@ static int opFSIN(uint32_t fetchdat)
         cpu_state.pc++;
         if (fplog) pclog("FSIN\n");
         ST(0) = sin(ST(0));
-        cpu_state.tag[cpu_state.TOP] &= ~TAG_UINT64;
+        cpu_state.tag[cpu_state.TOP] = TAG_VALID;
         cpu_state.npxs &= ~C2;
         CLOCK_CYCLES(300);
         return 0;
@@ -666,7 +666,7 @@ static int opFCOS(uint32_t fetchdat)
         cpu_state.pc++;
         if (fplog) pclog("FCOS\n");
         ST(0) = cos(ST(0));
-        cpu_state.tag[cpu_state.TOP] &= ~TAG_UINT64;
+        cpu_state.tag[cpu_state.TOP] = TAG_VALID;
         cpu_state.npxs &= ~C2;
         CLOCK_CYCLES(300);
         return 0;