diff --git a/Source/Core/VideoCommon/Src/PixelShaderGen.cpp b/Source/Core/VideoCommon/Src/PixelShaderGen.cpp
index a56f8dca62..1b50d6d540 100644
--- a/Source/Core/VideoCommon/Src/PixelShaderGen.cpp
+++ b/Source/Core/VideoCommon/Src/PixelShaderGen.cpp
@@ -58,8 +58,11 @@ void GetPixelShaderId(PIXELSHADERUID &uid, u32 texturemask, u32 dstAlphaEnable)
 
 	uid.values[2] = texturemask;
 
+    u32 enableZTexture = (!bpmem.zcontrol.zcomploc && bpmem.zmode.testenable && bpmem.zmode.updateenable)?1:0;
+
     uid.values[3] = (u32)bpmem.fog.c_proj_fsel.fsel |
-                   ((u32)bpmem.fog.c_proj_fsel.proj << 3);
+                   ((u32)bpmem.fog.c_proj_fsel.proj << 3) |
+                   ((u32)enableZTexture << 4);
 
 	int hdr = 4;
 	u32* pcurvalue = &uid.values[hdr];
@@ -522,11 +525,19 @@ const char *GeneratePixelShader(u32 texture_mask, bool dstAlphaEnable, u32 HLSL)
 	// the screen space depth value = far z + (clip z / clip w) * z range
 	WRITE(p, "float zCoord = "I_ZBIAS"[1].x + (clipPos.z / clipPos.w) * "I_ZBIAS"[1].y;\n");
 
-    // use the texture input of the last texture stage (textemp), hopefully this has been read and is in correct format...
-    if (bpmem.ztex2.op == ZTEXTURE_ADD)
-        WRITE(p, "zCoord = frac(dot("I_ZBIAS"[0].xyzw, textemp.xyzw) + "I_ZBIAS"[1].w + zCoord);\n");
-    else if (bpmem.ztex2.op == ZTEXTURE_REPLACE)
-        WRITE(p, "zCoord = frac(dot("I_ZBIAS"[0].xyzw, textemp.xyzw) + "I_ZBIAS"[1].w);\n");
+    if (bpmem.ztex2.op != ZTEXTURE_DISABLE && !bpmem.zcontrol.zcomploc && bpmem.zmode.testenable && bpmem.zmode.updateenable)
+    {
+        // use the texture input of the last texture stage (textemp), hopefully this has been read and is in correct format...
+        if (bpmem.ztex2.op == ZTEXTURE_ADD)
+            WRITE(p, "zCoord = dot("I_ZBIAS"[0].xyzw, textemp.xyzw) + "I_ZBIAS"[1].w + zCoord;\n");
+        else
+            WRITE(p, "zCoord = dot("I_ZBIAS"[0].xyzw, textemp.xyzw) + "I_ZBIAS"[1].w;\n");
+
+        // scale to make result from frac correct
+        WRITE(p, "zCoord = zCoord * (16777215.0f/16777216.0f);\n");
+        WRITE(p, "zCoord = frac(zCoord);\n");
+        WRITE(p, "zCoord = zCoord * (16777216.0f/16777215.0f);\n");
+    }
     
     WRITE(p, "depth = zCoord;\n");
 
diff --git a/Source/Core/VideoCommon/Src/PixelShaderManager.cpp b/Source/Core/VideoCommon/Src/PixelShaderManager.cpp
index f0a1a8ea08..9e516be8fb 100644
--- a/Source/Core/VideoCommon/Src/PixelShaderManager.cpp
+++ b/Source/Core/VideoCommon/Src/PixelShaderManager.cpp
@@ -106,22 +106,20 @@ void PixelShaderManager::SetConstants()
 
 	if (s_bZTextureTypeChanged) 
 	{    
-        static float ffrac = 255.0f/256.0f;
         float ftemp[4];
         switch (bpmem.ztex2.type) 
 		{
              case 0:
                 // 8 bits                
-                ftemp[0] = ffrac; ftemp[1] = 0; ftemp[2] = 0; ftemp[3] = 0;                
+                ftemp[0] = 0; ftemp[1] = 0; ftemp[2] = 0; ftemp[3] = 255.0f/16777215.0f;
                 break;
             case 1:
                 // 16 bits
-                ftemp[0] = ffrac/256.0f; ftemp[1] = 0; ftemp[2] = 0; ftemp[3] = ffrac;
+                ftemp[0] = 255.0f/16777215.0f; ftemp[1] = 0; ftemp[2] = 0; ftemp[3] = 65280.0f/16777215.0f;
                 break;
             case 2:
                 // 24 bits
-				//ftemp[0] = ffrac/65536.0f; ftemp[1] = ffrac/256.0f; ftemp[2] = ffrac; ftemp[3] = 0;
-				ftemp[0] = ffrac; ftemp[1] = ffrac/256.0f; ftemp[2] = ffrac/65536.0f; ftemp[3] = 0;
+				ftemp[0] = 16711680.0f/16777215.0f; ftemp[1] = 65280.0f/16777215.0f; ftemp[2] = 255.0f/16777215.0f; ftemp[3] = 0;
                 break;
         }
 		SetPSConstant4fv(C_ZBIAS, ftemp);
@@ -131,7 +129,7 @@ void PixelShaderManager::SetConstants()
 	if (s_bZBiasChanged || s_bDepthRangeChanged) 
 	{
         //ERROR_LOG("pixel=%x,%x, bias=%x\n", bpmem.zcontrol.pixel_format, bpmem.ztex2.type, lastZBias);
-        SetPSConstant4f(C_ZBIAS+1, lastDepthRange[0] / 16777216.0f, lastDepthRange[1] / 16777216.0f, 0, (float)( (((int)lastZBias<<8)>>8))/16777216.0f);
+        SetPSConstant4f(C_ZBIAS+1, lastDepthRange[0] / 16777216.0f, lastDepthRange[1] / 16777216.0f, 0, (float)(lastZBias)/16777215.0f);
 		s_bZBiasChanged = s_bDepthRangeChanged = false;
     }
 
diff --git a/Source/Plugins/Plugin_VideoSoftware/Src/Tev.cpp b/Source/Plugins/Plugin_VideoSoftware/Src/Tev.cpp
index 2d961b44b3..f4e764b920 100644
--- a/Source/Plugins/Plugin_VideoSoftware/Src/Tev.cpp
+++ b/Source/Plugins/Plugin_VideoSoftware/Src/Tev.cpp
@@ -676,10 +676,10 @@ void Tev::Draw()
     // z texture
     if (bpmem.ztex2.op)
     {
-        s32 ztex = bpmem.ztex1.bias;
+        u32 ztex = bpmem.ztex1.bias;
         switch (bpmem.ztex2.type) {
             case 0: // 8 bit
-                ztex += TexColor[RED_C];
+                ztex += TexColor[ALP_C];
                 break;
             case 1: // 16 bit
                 ztex += TexColor[ALP_C] << 8 | TexColor[RED_C];
@@ -689,14 +689,10 @@ void Tev::Draw()
                 break;
         }
 
-        switch (bpmem.ztex2.op) {
-            case ZTEXTURE_ADD:
-                Position[2] += ztex;
-                break;
-            case ZTEXTURE_REPLACE:
-                Position[2] = ztex;
-                break;
-        }
+        if (bpmem.ztex2.op == ZTEXTURE_ADD)
+            ztex += Position[2];
+
+        Position[2] = ztex & 0x00ffffff;
     }
 
     if (!bpmem.zcontrol.zcomploc && bpmem.zmode.testenable)