diff --git a/SConstruct b/SConstruct
index 3d0f5ec7b..cd454356b 100644
--- a/SConstruct
+++ b/SConstruct
@@ -53,7 +53,7 @@ AddOption('--cxx', dest='cxx', type='string', nargs=1, action='store', metavar='
 AddOption('--stxxlroot', dest='stxxlroot', type='string', nargs=1, action='store', metavar='STRING', help='root directory of STXXL')
 AddOption('--verbosity', dest='verbosity', type='string', nargs=1, action='store', metavar='STRING', help='make Scons talking')
 AddOption('--buildconfiguration', dest='buildconfiguration', type='string', nargs=1, action='store', metavar='STRING', help='debug or release')
-env = Environment(COMPILER = GetOption('cxx'))
+env = Environment(ENV = {'PATH' : os.environ['PATH']} ,COMPILER = GetOption('cxx'))
 if GetOption('cxx') is None:
     #default Compiler
     print 'Using default C++ Compiler: ', env['CXX']
@@ -83,7 +83,10 @@ else:
 conf = Configure(env, custom_tests = { 'CheckBoost' : CheckBoost, 'CheckProtobuf' : CheckProtobuf })
 if not conf.CheckHeader('omp.h'):
 	print "Compiler does not support OpenMP. Exiting"
-	Exit(-1)
+	if sys.platform == 'darwin':
+		print "Continuing because we are on Mac. This might be fatal."
+	else:
+		Exit(-1)
 if not conf.CheckLibWithHeader('xml2', 'libxml/xmlreader.h', 'CXX'):
 	print "libxml2 library or header not found. Exiting"
 	Exit(-1)
diff --git a/Util/MachineInfo.h b/Util/MachineInfo.h
new file mode 100644
index 000000000..849052cb6
--- /dev/null
+++ b/Util/MachineInfo.h
@@ -0,0 +1,49 @@
+/*
+ open source routing machine
+ Copyright (C) Dennis Luxen, others 2010
+ 
+ This program is free software; you can redistribute it and/or modify
+ it under the terms of the GNU AFFERO General Public License as published by
+ the Free Software Foundation; either version 3 of the License, or
+ any later version.
+ 
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ GNU General Public License for more details.
+ 
+ You should have received a copy of the GNU Affero General Public License
+ along with this program; if not, write to the Free Software
+ Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ or see http://www.gnu.org/licenses/agpl.txt.
+ */
+
+#ifndef MACHINE_INFO_H
+#define MACHINE_INFO_H
+
+#ifdef __APPLE__
+extern "C" {
+#include <sys/sysctl.h>
+}	
+#endif
+
+/* Returns the physical memory size in kilobytes */
+unsigned GetPhysicalmemory(void){
+#if defined(SUN5) || defined(LINUX)
+	return (sysconf(_SC_PHYS_PAGES) * sysconf(_SC_PAGESIZE));
+	
+#elif defined(__APPLE__)
+	int mib[2] = {CTL_HW, HW_MEMSIZE};
+	long long memsize;
+	size_t len;
+	
+	len = sizeof(memsize);
+	sysctl(mib, 2, &memsize, &len, NULL, 0);
+    
+	return memsize/1024;
+#else
+	std::cout << "[Warning] Compiling on unknown architecture." << std::endl << "Please file a ticket at http://project-osrm.org" << std::endl;
+	return 2048*1024; /* 128 Mb default memory */
+#endif
+}
+#endif
\ No newline at end of file
diff --git a/extractor.cpp b/extractor.cpp
index 791a0384b..4767b559a 100644
--- a/extractor.cpp
+++ b/extractor.cpp
@@ -46,6 +46,7 @@ or see http://www.gnu.org/licenses/agpl.txt.
 #include "DataStructures/XMLParser.h"
 #include "Util/BaseConfiguration.h"
 #include "Util/InputFileUtil.h"
+#include "Util/MachineInfo.h"
 
 typedef BaseConfiguration ExtractorConfiguration;
 
@@ -62,7 +63,7 @@ bool removeIfUnused(ClassT n) { return (false == n.used); }
 
 int main (int argc, char *argv[]) {
     if(argc <= 1) {
-        std::cerr << "usage: " << endl << argv[0] << " <file.osm>" << std::endl;
+        std::cerr << "usage: " << endl << argv[0] << " <file.osm/.osm.bz2/.osm.pbf>" << std::endl;
         exit(-1);
     }
 
@@ -91,8 +92,8 @@ int main (int argc, char *argv[]) {
 
 
     unsigned amountOfRAM = 1;
-    unsigned installedRAM = (sysconf(_SC_PHYS_PAGES) * sysconf(_SC_PAGESIZE));
-    if(installedRAM < 2097422336) {
+    unsigned installedRAM = GetPhysicalmemory(); 
+	if(installedRAM < 2048264) {
         std::cout << "[Warning] Machine has less than 2GB RAM." << std::endl;
     }
     if(testDataFile("extractor.ini")) {