diff --git a/neo/CMakeLists.txt b/neo/CMakeLists.txt
index b95fc3cb..c8eba3da 100644
--- a/neo/CMakeLists.txt
+++ b/neo/CMakeLists.txt
@@ -74,7 +74,15 @@ elseif(cpu MATCHES "i.86")
 endif()
 
 if(MSVC AND CMAKE_CL_64)
-	set(cpu "amd64")
+	set(cpu "x86_64")
+endif()
+
+add_definitions(-DD3_ARCH="${cpu}" -DD3_SIZEOFPTR=${CMAKE_SIZEOF_VOID_P})
+
+if(cpu STREQUAL "x86_64" AND NOT CMAKE_SIZEOF_VOID_P EQUAL 8)
+	# TODO: same for arm64? PPC64?
+	message(SEND_ERROR "CMake thinks sizeof(void*) == 4, but that the target CPU is x86_64!")
+	message(FATAL_ERROR "If you're building in a 32bit chroot on a 64bit host, switch to it with 'linux32 chroot' or at least call cmake with linux32 (or your OSs equivalent)!")
 endif()
 
 # target os
@@ -84,6 +92,8 @@ else()
 	string(TOLOWER "${CMAKE_SYSTEM_NAME}" os)
 endif()
 
+add_definitions(-DD3_OSTYPE="${os}")
+
 # build type
 if(NOT CMAKE_BUILD_TYPE)
 	set(CMAKE_BUILD_TYPE "RelWithDebInfo")
@@ -230,7 +240,7 @@ if(CMAKE_COMPILER_IS_GNUCC OR CMAKE_C_COMPILER_ID STREQUAL "Clang")
 		if(cpu STREQUAL "x86_64")
 			add_compile_options(-arch x86_64 -mmacosx-version-min=10.9)
 			set(ldflags "${ldflags} -arch x86_64 -mmacosx-version-min=10.9")
-                elseif(cpu STREQUAL "arm64")
+		elseif(cpu STREQUAL "arm64")
 			add_compile_options(-arch arm64 -mmacosx-version-min=11.0)
 			set(ldflags "${ldflags} -arch arm64 -mmacosx-version-min=11.0")
 		elseif(cpu STREQUAL "x86")
diff --git a/neo/d3xp/Game_local.cpp b/neo/d3xp/Game_local.cpp
index 6ffb61b1..08aaf9bf 100644
--- a/neo/d3xp/Game_local.cpp
+++ b/neo/d3xp/Game_local.cpp
@@ -26,6 +26,8 @@ If you have questions concerning this license or the applicable additional terms
 ===========================================================================
 */
 
+#include <SDL_endian.h>
+
 #include "sys/platform.h"
 #include "idlib/LangDict.h"
 #include "idlib/Timer.h"
@@ -505,6 +507,15 @@ void idGameLocal::SaveGame( idFile *f ) {
 
 	savegame.WriteBuildNumber( BUILD_NUMBER );
 
+	// DG: add some more information to savegame to make future quirks easier
+	savegame.WriteInt( INTERNAL_SAVEGAME_VERSION ); // to be independent of BUILD_NUMBER
+	savegame.WriteString( D3_OSTYPE ); // operating system - from CMake
+	savegame.WriteString( D3_ARCH ); // CPU architecture (e.g. "x86" or "x86_64") - from CMake
+	savegame.WriteString( ENGINE_VERSION );
+	savegame.WriteShort( (short)sizeof(void*) ); // tells us if it's from a 32bit (4) or 64bit system (8)
+	savegame.WriteShort( SDL_BYTEORDER ) ; // SDL_LIL_ENDIAN or SDL_BIG_ENDIAN
+	// DG end
+
 	// go through all entities and threads and add them to the object list
 	for( i = 0; i < MAX_GENTITIES; i++ ) {
 		ent = entities[i];
@@ -1360,6 +1371,36 @@ bool idGameLocal::InitFromSaveGame( const char *mapName, idRenderWorld *renderWo
 
 	savegame.ReadBuildNumber();
 
+	// DG: I enhanced the information in savegames a bit for dhewm3 1.5.1
+	//     for which I bumped th BUILD_NUMBER to 1305
+	if( savegame.GetBuildNumber() >= 1305 )
+	{
+		savegame.ReadInternalSavegameVersion();
+		if( savegame.GetInternalSavegameVersion() > INTERNAL_SAVEGAME_VERSION ) {
+			Warning( "Savegame from newer dhewm3 version, don't know how to load! (its version is %d, only up to %d supported)",
+			         savegame.GetInternalSavegameVersion(), INTERNAL_SAVEGAME_VERSION );
+			return false;
+		}
+		idStr osType;
+		idStr cpuArch;
+		idStr engineVersion;
+		short ptrSize = 0;
+		short byteorder = 0;
+		savegame.ReadString( osType ); // operating system the savegame was crated on (written from D3_OSTYPE)
+		savegame.ReadString( cpuArch ); // written from D3_ARCH (which is set in CMake), like "x86" or "x86_64"
+		savegame.ReadString( engineVersion ); // written from ENGINE_VERSION
+		savegame.ReadShort( ptrSize ); // sizeof(void*) of system that created the savegame, 4 on 32bit systems, 8 on 64bit systems
+		savegame.ReadShort( byteorder ); // SDL_LIL_ENDIAN or SDL_BIG_ENDIAN
+
+		Printf( "Savegame was created by %s on %s %s. BuildNumber was %d, savegameversion %d\n",
+		        engineVersion.c_str(), osType.c_str(), cpuArch.c_str(), savegame.GetBuildNumber(),
+		        savegame.GetInternalSavegameVersion() );
+
+		// right now I have no further use for this information, but in the future
+		// it can be used for quirks for (then-) old savegames
+	}
+	// DG end
+
 	// Create the list of all objects in the game
 	savegame.CreateObjects();
 
diff --git a/neo/d3xp/Game_local.h b/neo/d3xp/Game_local.h
index cb229cd9..acd4fff0 100644
--- a/neo/d3xp/Game_local.h
+++ b/neo/d3xp/Game_local.h
@@ -512,6 +512,7 @@ public:
 
 private:
 	const static int		INITIAL_SPAWN_COUNT = 1;
+	const static int		INTERNAL_SAVEGAME_VERSION = 1; // DG: added this for >= 1305 savegames
 
 	idStr					mapFileName;			// name of the map, empty string if no map loaded
 	idMapFile *				mapFile;				// will be NULL during the game unless in-game editing is used
diff --git a/neo/d3xp/gamesys/SaveGame.cpp b/neo/d3xp/gamesys/SaveGame.cpp
index 2dd04a66..83414a91 100644
--- a/neo/d3xp/gamesys/SaveGame.cpp
+++ b/neo/d3xp/gamesys/SaveGame.cpp
@@ -785,6 +785,7 @@ idRestoreGame::RestoreGame
 */
 idRestoreGame::idRestoreGame( idFile *savefile ) {
 	file = savefile;
+	internalSavegameVersion = 0;
 }
 
 /*
diff --git a/neo/d3xp/gamesys/SaveGame.h b/neo/d3xp/gamesys/SaveGame.h
index 4b0927f4..b7816597 100644
--- a/neo/d3xp/gamesys/SaveGame.h
+++ b/neo/d3xp/gamesys/SaveGame.h
@@ -158,8 +158,23 @@ public:
 	//						Used to retrieve the saved game buildNumber from within class Restore methods
 	int						GetBuildNumber( void );
 
+	// DG: added these methods, internalSavegameVersion makes us independent of the global BUILD_NUMBER
+	void					ReadInternalSavegameVersion( void )
+	{
+		ReadInt( internalSavegameVersion );
+	}
+
+	// if it's 0, this is from a GetBuildNumber() < 1305 savegame
+	// otherwise, compare it to idGameLocal::INTERNAL_SAVEGAME_VERSION
+	int						GetInternalSavegameVersion( void ) const
+	{
+		return internalSavegameVersion;
+	}
+	// DG end
+
 private:
 	int						buildNumber;
+	int						internalSavegameVersion; // DG added this
 
 	idFile *				file;
 
diff --git a/neo/framework/Common.cpp b/neo/framework/Common.cpp
index 87d9df69..d0bda134 100644
--- a/neo/framework/Common.cpp
+++ b/neo/framework/Common.cpp
@@ -2837,6 +2837,24 @@ static bool checkForHelp(int argc, char **argv)
 	return false;
 }
 
+#ifdef UINTPTR_MAX // DG: make sure D3_SIZEOFPTR is consistent with reality
+
+#if D3_SIZEOFPTR == 4
+  #if UINTPTR_MAX != 0xFFFFFFFFUL
+    #error "CMake assumes that we're building for a 32bit architecture, but UINTPTR_MAX doesn't match!"
+  #endif
+#elif D3_SIZEOFPTR == 8
+  #if UINTPTR_MAX != 18446744073709551615ULL
+    #error "CMake assumes that we're building for a 64bit architecture, but UINTPTR_MAX doesn't match!"
+  #endif
+#else
+  // Hello future person with a 128bit(?) CPU, I hope the future doesn't suck too much and that you don't still use CMake.
+  // Also, please adapt this check and send a pull request (or whatever way we have to send patches in the future)
+  #error "D3_SIZEOFPTR should really be 4 (for 32bit targets) or 8 (for 64bit targets), what kind of machine is this?!"
+#endif
+
+#endif // UINTPTR_MAX defined
+
 /*
 =================
 idCommonLocal::Init
@@ -2844,6 +2862,12 @@ idCommonLocal::Init
 */
 void idCommonLocal::Init( int argc, char **argv ) {
 
+	// in case UINTPTR_MAX isn't defined (or wrong), do a runtime check at startup
+	if ( D3_SIZEOFPTR != sizeof(void*) ) {
+		Sys_Error( "Something went wrong in your build: CMake assumed that sizeof(void*) == %d but in reality it's %d!\n",
+		           (int)D3_SIZEOFPTR, (int)sizeof(void*) );
+	}
+
 	if(checkForHelp(argc, argv))
 	{
 		// game has been started with --help (or similar), usage message has been shown => quit
diff --git a/neo/framework/Licensee.h b/neo/framework/Licensee.h
index dcf75071..f9b4c8c1 100644
--- a/neo/framework/Licensee.h
+++ b/neo/framework/Licensee.h
@@ -41,12 +41,12 @@ If you have questions concerning this license or the applicable additional terms
 #define GAME_NAME						"dhewm 3"		// appears on window titles and errors
 #endif
 
-#define ENGINE_VERSION					"dhewm3 1.5.1rc2"	// printed in console
+#define ENGINE_VERSION					"dhewm3 1.5.1rc3"	// printed in console
 
 #ifdef ID_REPRODUCIBLE_BUILD
 	// for reproducible builds we hardcode values that would otherwise come from __DATE__ and __TIME__
 	// NOTE: remember to update esp. the date for (pre-) releases and RCs and the like
-	#define ID__DATE__  "Jul 21 2020"
+	#define ID__DATE__  "Feb 06 2021"
 	#define ID__TIME__  "13:37:42"
 
 #else // not reproducible build, use __DATE__ and __TIME__ macros
diff --git a/neo/game/Game_local.cpp b/neo/game/Game_local.cpp
index d99901cb..ef820d66 100644
--- a/neo/game/Game_local.cpp
+++ b/neo/game/Game_local.cpp
@@ -26,6 +26,8 @@ If you have questions concerning this license or the applicable additional terms
 ===========================================================================
 */
 
+#include <SDL_endian.h>
+
 #include "sys/platform.h"
 #include "idlib/LangDict.h"
 #include "idlib/Timer.h"
@@ -447,9 +449,14 @@ void idGameLocal::SaveGame( idFile *f ) {
 
 	savegame.WriteBuildNumber( BUILD_NUMBER );
 
-	// DG: TODO: write other things (maybe internal savegame version so I don't have to bump BUILD_NUMBER AGAIN)
-	//           and OS, architecture etc, see #344
-	// TODO: adjust InitFromSavegame() accordingly!
+	// DG: add some more information to savegame to make future quirks easier
+	savegame.WriteInt( INTERNAL_SAVEGAME_VERSION ); // to be independent of BUILD_NUMBER
+	savegame.WriteString( D3_OSTYPE ); // operating system - from CMake
+	savegame.WriteString( D3_ARCH ); // CPU architecture (e.g. "x86" or "x86_64") - from CMake
+	savegame.WriteString( ENGINE_VERSION );
+	savegame.WriteShort( (short)sizeof(void*) ); // tells us if it's from a 32bit (4) or 64bit system (8)
+	savegame.WriteShort( SDL_BYTEORDER ) ; // SDL_LIL_ENDIAN or SDL_BIG_ENDIAN
+	// DG end
 
 	// go through all entities and threads and add them to the object list
 	for( i = 0; i < MAX_GENTITIES; i++ ) {
@@ -1244,11 +1251,35 @@ bool idGameLocal::InitFromSaveGame( const char *mapName, idRenderWorld *renderWo
 
 	savegame.ReadBuildNumber();
 
-
-	if(savegame.GetBuildNumber() >= 1305)
+	// DG: I enhanced the information in savegames a bit for dhewm3 1.5.1
+	//     for which I bumped th BUILD_NUMBER to 1305
+	if( savegame.GetBuildNumber() >= 1305 )
 	{
-		// TODO: read stuff additionally written in SaveGame()
+		savegame.ReadInternalSavegameVersion();
+		if( savegame.GetInternalSavegameVersion() > INTERNAL_SAVEGAME_VERSION ) {
+			Warning( "Savegame from newer dhewm3 version, don't know how to load! (its version is %d, only up to %d supported)",
+			         savegame.GetInternalSavegameVersion(), INTERNAL_SAVEGAME_VERSION );
+			return false;
+		}
+		idStr osType;
+		idStr cpuArch;
+		idStr engineVersion;
+		short ptrSize = 0;
+		short byteorder = 0;
+		savegame.ReadString( osType ); // operating system the savegame was crated on (written from D3_OSTYPE)
+		savegame.ReadString( cpuArch ); // written from D3_ARCH (which is set in CMake), like "x86" or "x86_64"
+		savegame.ReadString( engineVersion ); // written from ENGINE_VERSION
+		savegame.ReadShort( ptrSize ); // sizeof(void*) of system that created the savegame, 4 on 32bit systems, 8 on 64bit systems
+		savegame.ReadShort( byteorder ); // SDL_LIL_ENDIAN or SDL_BIG_ENDIAN
+
+		Printf( "Savegame was created by %s on %s %s. BuildNumber was %d, savegameversion %d\n",
+		        engineVersion.c_str(), osType.c_str(), cpuArch.c_str(), savegame.GetBuildNumber(),
+		        savegame.GetInternalSavegameVersion() );
+
+		// right now I have no further use for this information, but in the future
+		// it can be used for quirks for (then-) old savegames
 	}
+	// DG end
 
 	// Create the list of all objects in the game
 	savegame.CreateObjects();
diff --git a/neo/game/Game_local.h b/neo/game/Game_local.h
index 1f724434..df7456d1 100644
--- a/neo/game/Game_local.h
+++ b/neo/game/Game_local.h
@@ -450,6 +450,7 @@ public:
 
 private:
 	const static int		INITIAL_SPAWN_COUNT = 1;
+	const static int		INTERNAL_SAVEGAME_VERSION = 1; // DG: added this for >= 1305 savegames
 
 	idStr					mapFileName;			// name of the map, empty string if no map loaded
 	idMapFile *				mapFile;				// will be NULL during the game unless in-game editing is used
diff --git a/neo/game/gamesys/SaveGame.cpp b/neo/game/gamesys/SaveGame.cpp
index e0b70c9d..7dceafeb 100644
--- a/neo/game/gamesys/SaveGame.cpp
+++ b/neo/game/gamesys/SaveGame.cpp
@@ -780,6 +780,7 @@ idRestoreGame::RestoreGame
 */
 idRestoreGame::idRestoreGame( idFile *savefile ) {
 	file = savefile;
+	internalSavegameVersion = 0;
 }
 
 /*
diff --git a/neo/game/gamesys/SaveGame.h b/neo/game/gamesys/SaveGame.h
index 4b0927f4..b7816597 100644
--- a/neo/game/gamesys/SaveGame.h
+++ b/neo/game/gamesys/SaveGame.h
@@ -158,8 +158,23 @@ public:
 	//						Used to retrieve the saved game buildNumber from within class Restore methods
 	int						GetBuildNumber( void );
 
+	// DG: added these methods, internalSavegameVersion makes us independent of the global BUILD_NUMBER
+	void					ReadInternalSavegameVersion( void )
+	{
+		ReadInt( internalSavegameVersion );
+	}
+
+	// if it's 0, this is from a GetBuildNumber() < 1305 savegame
+	// otherwise, compare it to idGameLocal::INTERNAL_SAVEGAME_VERSION
+	int						GetInternalSavegameVersion( void ) const
+	{
+		return internalSavegameVersion;
+	}
+	// DG end
+
 private:
 	int						buildNumber;
+	int						internalSavegameVersion; // DG added this
 
 	idFile *				file;