"-thread" allows negative values.

sp/src/utils/common/threads.cpp

@@ -112,7 +112,11 @@ WIN32
 ===================================================================
 */
 
+#ifdef MAPBASE
+int		numthreads = -(MAX_TOOL_THREADS + 1);
+#else
 int		numthreads = -1;
+#endif
 CRITICAL_SECTION		crit;
 static int enter;
 
@@ -133,19 +137,37 @@ void SetLowPriority()
 	SetPriorityClass( GetCurrentProcess(), IDLE_PRIORITY_CLASS );
 }
 
-
+//Threads can be negative; if so, they will be subtracted from the total thread count.
 void ThreadSetDefault (void)
 {
 	SYSTEM_INFO info;
 
+#ifdef MAPBASE
+	if (numthreads == -(MAX_TOOL_THREADS + 1))	// not set manually
+#else
 	if (numthreads == -1)	// not set manually
+#endif
 	{
 		GetSystemInfo (&info);
 		numthreads = info.dwNumberOfProcessors;
+#ifdef MAPBASE
+		if (numthreads > 32)
+#else
 		if (numthreads < 1 ||numthreads > 32)
+#endif
 			numthreads = 1;
 	}
 
+#ifdef MAPBASE
+	if (numthreads <= 0) 
+	{
+		GetSystemInfo(&info);
+		numthreads = info.dwNumberOfProcessors + numthreads;
+		if (numthreads <= 0)
+			Error("\nIncrease the number of threads! Threads: %i, they cannot be negative or 0.\n", numthreads);
+	}
+#endif
+
 	Msg ("%i threads\n", numthreads);
 }
 

sp/src/utils/vbsp/vbsp.cpp

@@ -1313,8 +1313,9 @@ int RunVBSP( int argc, char **argv )
 			Warning(
 				"Other options  :\n"
 				"  -novconfig   : Don't bring up graphical UI on vproject errors.\n"
-				"  -threads     : Control the number of threads vbsp uses (defaults to the # of\n"
+				"  -threads #   : Control the number of threads vbsp uses (defaults to the #\n"
-				"                 processors on your machine).\n"
+				"                or processors on your machine).\n"
+				"				 Threads can be negative; if so, they will be subtracted from the total thread count.\n"
 				"  -verboseentities: If -v is on, this disables verbose output for submodels.\n"
 				"  -noweld      : Don't join face vertices together.\n"
 				"  -nocsg       : Don't chop out intersecting brush areas.\n"

sp/src/utils/vrad/vrad.cpp

@@ -2431,11 +2431,13 @@ int ParseCommandLine( int argc, char **argv, bool *onlydetail )
 			if ( ++i < argc )
 			{
 				numthreads = atoi (argv[i]);
+#ifndef MAPBASE //Mapbase allows threads to be negative, go to ThreadSetDefault(void) in threads.cpp for a explanation.
 				if ( numthreads <= 0 )
 				{
 					Warning("Error: expected positive value after '-threads'\n" );
 					return 1;
 				}
+#endif
 			}
 			else
 			{
@@ -2827,8 +2829,9 @@ void PrintUsage( int argc, char **argv )
 		"  -dump           : Write debugging .txt files.\n"
 		"  -dumpnormals    : Write normals to debug files.\n"
 		"  -dumptrace      : Write ray-tracing environment to debug files.\n"
-		"  -threads        : Control the number of threads vbsp uses (defaults to the #\n"
+		"  -threads #      : Control the number of threads vrad uses (defaults to the #\n"
 		"                    or processors on your machine).\n"
+		"					 Threads can be negative; if so, they will be subtracted from the total thread count.\n"
 		"  -lights <file>  : Load a lights file in addition to lights.rad and the\n"
 		"                    level lights file.\n"
 		"  -noextra        : Disable supersampling.\n"

sp/src/utils/vvis/vvis.cpp

@@ -1027,8 +1027,9 @@ void PrintUsage( int argc, char **argv )
 		"  -novconfig      : Don't bring up graphical UI on vproject errors.\n"
 		"  -radius_override: Force a vis radius, regardless of whether an\n"
 		"  -mpi_pw <pw>    : Use a password to choose a specific set of VMPI workers.\n"
-		"  -threads        : Control the number of threads vbsp uses (defaults to the #\n"
+		"  -threads #      : Control the number of threads vvis uses (defaults to the #\n"
 		"                    or processors on your machine).\n"
+		"					 Threads can be negative; if so, they will be subtracted from the total thread count.\n"
 		"  -nosort         : Don't sort portals (sorting is an optimization).\n"
 		"  -tmpin          : Make portals come from \\tmp\\<mapname>.\n"
 		"  -tmpout         : Make portals come from \\tmp\\<mapname>.\n"