diff --git a/CMakeLists.txt b/CMakeLists.txt
index 5348393..769be70 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -19,13 +19,13 @@ set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Wall -fno-strict-aliasing -fwrapv")
 string(REPLACE "-O3" "-O2" CMAKE_C_FLAGS_RELEASE "${CMAKE_C_FLAGS_RELEASE}")
 
 # Operating system
-add_definitions(-DOSTYPE="${CMAKE_SYSTEM_NAME}")
+add_definitions(-DYQ2OSTYPE="${CMAKE_SYSTEM_NAME}")
 
 # Architecture string
 string(REGEX REPLACE "amd64" "x86_64" ARCH "${CMAKE_SYSTEM_PROCESSOR}")
 string(REGEX REPLACE "i.86" "i386" ARCH "${ARCH}")
 string(REGEX REPLACE "^arm.*" "arm" ARCH "${ARCH}")
-add_definitions(-DARCH="${ARCH}")
+add_definitions(-DYQ2ARCH="${ARCH}")
 
 # Linker Flags
 if(${CMAKE_SYSTEM_NAME} MATCHES "Windows")
diff --git a/Makefile b/Makefile
index f1f860a..9819467 100644
--- a/Makefile
+++ b/Makefile
@@ -16,28 +16,36 @@
 
 # Detect the OS
 ifdef SystemRoot
-OSTYPE := Windows
+YQ2_OSTYPE := Windows
 else
-OSTYPE := $(shell uname -s)
+YQ2_OSTYPE := $(shell uname -s)
 endif
 
 # Special case for MinGW
-ifneq (,$(findstring MINGW,$(OSTYPE)))
-OSTYPE := Windows
+ifneq (,$(findstring MINGW,$(YQ2_OSTYPE)))
+YQ2_OSTYPE := Windows
 endif
 
 # Detect the architecture
-ifeq ($(OSTYPE), Windows)
+ifeq ($(YQ2_OSTYPE), Windows)
+ifdef MINGW_CHOST
+ifeq ($(MINGW_CHOST), x86_64-w64-mingw32)
+YQ2_ARCH ?= x86_64
+else # i686-w64-mingw32
+YQ2_ARCH ?= i386
+endif
+else # windows, but MINGW_CHOST not defined
 ifdef PROCESSOR_ARCHITEW6432
 # 64 bit Windows
-ARCH := $(PROCESSOR_ARCHITEW6432)
+YQ2_ARCH ?= $(PROCESSOR_ARCHITEW6432)
 else
 # 32 bit Windows
-ARCH := $(PROCESSOR_ARCHITECTURE)
+YQ2_ARCH ?= $(PROCESSOR_ARCHITECTURE)
 endif
+endif # windows but MINGW_CHOST not defined
 else
-# Normalize some abiguous ARCH strings
-ARCH := $(shell uname -m | sed -e 's/i.86/i386/' -e 's/amd64/x86_64/' -e 's/^arm.*/arm/')
+# Normalize some abiguous YQ2_ARCH strings
+YQ2_ARCH ?= $(shell uname -m | sed -e 's/i.86/i386/' -e 's/amd64/x86_64/' -e 's/^arm.*/arm/')
 endif
 
 # Detect the compiler
@@ -71,7 +79,7 @@ endif
 # -fPIC for position independend code.
 #
 # -MMD to generate header dependencies.
-ifeq ($(OSTYPE), Darwin)
+ifeq ($(YQ2_OSTYPE), Darwin)
 CFLAGS := -O2 -fno-strict-aliasing -fomit-frame-pointer \
 		  -Wall -pipe -g -fwrapv -arch i386 -arch x86_64
 else
@@ -97,13 +105,23 @@ endif
 
 # ----------
 
+# Using the default x87 float math on 32bit x86 causes rounding trouble
+# -ffloat-store could work around that, but the better solution is to
+# just enforce SSE - every x86 CPU since Pentium3 supports that
+# and this should even improve the performance on old CPUs
+ifeq ($(YQ2_ARCH), i386)
+override CFLAGS += -msse -mfpmath=sse
+endif
+
+# ----------
+
 # Defines the operating system and architecture
-CFLAGS += -DOSTYPE=\"$(OSTYPE)\" -DARCH=\"$(ARCH)\"
+CFLAGS += -DYQ2OSTYPE=\"$(YQ2_OSTYPE)\" -DYQ2ARCH=\"$(YQ2_ARCH)\"
 
 # ----------
 
 # Base LDFLAGS.
-ifeq ($(OSTYPE), Darwin)
+ifeq ($(YQ2_OSTYPE), Darwin)
 LDFLAGS := -shared -arch i386 -arch x86_64
 else
 LDFLAGS := -shared
@@ -140,7 +158,7 @@ clean:
 # ----------
 
 # The zaero game
-ifeq ($(OSTYPE), Windows)
+ifeq ($(YQ2_OSTYPE), Windows)
 zaero:
 	@echo "===> Building game.dll"
 	${Q}mkdir -p release
@@ -246,7 +264,7 @@ ZAERO_DEPS= $(ZAERO_OBJS:.o=.d)
 
 # ----------
 
-ifeq ($(OSTYPE), Windows)
+ifeq ($(YQ2_OSTYPE), Windows)
 release/game.dll : $(ZAERO_OBJS)
 	@echo "===> LD $@"
 	${Q}$(CC) $(LDFLAGS) -o $@ $(ZAERO_OBJS)
diff --git a/src/savegame/savegame.c b/src/savegame/savegame.c
index ea80e21..741b080 100644
--- a/src/savegame/savegame.c
+++ b/src/savegame/savegame.c
@@ -54,19 +54,19 @@
  * in tables/ are changed, otherwise
  * strange things may happen.
  */
-#define SAVEGAMEVER "YQ2-3"
+#define SAVEGAMEVER "YQ2-4"
 
 /*
  * This macros are used to prohibit loading of savegames
  * created on other systems or architectures. This will
  * crash q2 in spectacular ways
  */
-#ifndef OSTYPE
-#error OSTYPE should be defined by the build system
+#ifndef YQ2OSTYPE
+#error YQ2OSTYPE should be defined by the build system
 #endif
 
-#ifndef ARCH
-#error ARCH should be defined by the build system
+#ifndef YQ2ARCH
+#error YQ2ARCH should be defined by the build system
 #endif
 
 /*
@@ -766,8 +766,8 @@ WriteGame(const char *filename, qboolean autosave)
 
 	strncpy(str_ver, SAVEGAMEVER, sizeof(str_ver));
 	strncpy(str_game, GAMEVERSION, sizeof(str_game));
-	strncpy(str_os, OSTYPE, sizeof(str_os) - 1);
-    strncpy(str_arch, ARCH, sizeof(str_arch));
+	strncpy(str_os, YQ2OSTYPE, sizeof(str_os) - 1);
+	strncpy(str_arch, YQ2ARCH, sizeof(str_arch));
 
 	fwrite(str_ver, sizeof(str_ver), 1, f);
 	fwrite(str_game, sizeof(str_game), 1, f);
@@ -817,85 +817,87 @@ ReadGame(const char *filename)
 	fread(str_os, sizeof(str_os), 1, f);
 	fread(str_arch, sizeof(str_arch), 1, f);
 
-	if (!strcmp(str_ver, SAVEGAMEVER))
-	{
-		save_ver = 3;
+	static const struct {
+		const char* verstr;
+		int vernum;
+	} version_mappings[] = {
+		{"YQ2-1", 1},
+		{"YQ2-2", 2},
+		{"YQ2-3", 3},
+		{"YQ2-4", 4},
+	};
 
-		if (strcmp(str_game, GAMEVERSION))
+	for (i=0; i < sizeof(version_mappings)/sizeof(version_mappings[0]); ++i)
+	{
+		if (strcmp(version_mappings[i].verstr, str_ver) == 0)
 		{
-			fclose(f);
-			gi.error("Savegame from an other game.so.\n");
-		}
-		else if (strcmp(str_os, OSTYPE))
-		{
-			fclose(f);
-			gi.error("Savegame from an other os.\n");
-		}
-		else if (strcmp(str_arch, ARCH))
-		{
-			fclose(f);
-			gi.error("Savegame from an other architecure.\n");
+			save_ver = version_mappings[i].vernum;
+			break;
 		}
 	}
-	else if (!strcmp(str_ver, "YQ2-2"))
-	{
-		save_ver = 2;
 
-		if (strcmp(str_game, GAMEVERSION))
-		{
-			fclose(f);
-			gi.error("Savegame from an other game.so.\n");
-		}
-		else if (strcmp(str_os, OSTYPE))
-		{
-			fclose(f);
-			gi.error("Savegame from an other os.\n");
-		}
-		else if (strcmp(str_arch, ARCH))
-		{
-			fclose(f);
-			gi.error("Savegame from an other architecure.\n");
-		}
-	}
-	else if (!strcmp(str_ver, "YQ2-1"))
-	{
-		save_ver = 1;
-
-		if (strcmp(str_game, GAMEVERSION))
-		{
-			fclose(f);
-			gi.error("Savegame from an other game.so.\n");
-		}
-		else if (strcmp(str_os, OSTYPE_1))
-		{
-			fclose(f);
-			gi.error("Savegame from an other os.\n");
-		}
-
-		if (!strcmp(str_os, "Windows"))
-		{
-			/* Windows was forced to i386 */
-			if (strcmp(str_arch, "i386"))
-			{
-				fclose(f);
-				gi.error("Savegame from an other architecure.\n");
-			}
-		}
-		else
-		{
-			if (strcmp(str_arch, ARCH_1))
-			{
-				fclose(f);
-				gi.error("Savegame from an other architecure.\n");
-			}
-		}
-	}
-	else
+	if (save_ver == 0) // not found in mappings table
 	{
 		fclose(f);
 		gi.error("Savegame from an incompatible version.\n");
 	}
- 
+
+	if (save_ver == 1)
+	{
+		if (strcmp(str_game, GAMEVERSION) != 0)
+		{
+			fclose(f);
+			gi.error("Savegame from another game.so.\n");
+		}
+		else if (strcmp(str_os, OSTYPE_1) != 0)
+		{
+			fclose(f);
+			gi.error("Savegame from another os.\n");
+		}
+
+#ifdef _WIN32
+		/* Windows was forced to i386 */
+		if (strcmp(str_arch, "i386") != 0)
+		{
+			fclose(f);
+			gi.error("Savegame from another architecture.\n");
+		}
+#else
+		if (strcmp(str_arch, ARCH_1) != 0)
+		{
+			fclose(f);
+			gi.error("Savegame from another architecture.\n");
+		}
+#endif
+	}
+	else // all newer savegame versions
+	{
+		if (strcmp(str_game, GAMEVERSION) != 0)
+		{
+			fclose(f);
+			gi.error("Savegame from another game.so.\n");
+		}
+		else if (strcmp(str_os, YQ2OSTYPE) != 0)
+		{
+			fclose(f);
+			gi.error("Savegame from another os.\n");
+		}
+		else if (strcmp(str_arch, YQ2ARCH) != 0)
+		{
+#if defined(_WIN32) && (defined(__i386__) || defined(_M_IX86))
+			// before savegame version "YQ2-4" (and after version 1),
+			// the official Win32 binaries accidentally had the YQ2ARCH "AMD64"
+			// instead of "i386" set due to a bug in the Makefile.
+			// This quirk allows loading those savegames anyway
+			if (save_ver >= 4 || strcmp(str_arch, "AMD64") != 0)
+#endif
+			{
+				fclose(f);
+				gi.error("Savegame from another architecture.\n");
+			}
+		}
+	}
+
 	g_edicts = gi.TagMalloc(game.maxentities * sizeof(g_edicts[0]), TAG_GAME);
 	globals.edicts = g_edicts;