diff --git a/Make.config b/Make.config
index 673608c612..536e6c17f2 100644
--- a/Make.config
+++ b/Make.config
@@ -154,9 +154,9 @@ override IOS_DESTDIR := $(patsubst %/,%,$(abspath $(IOS_DESTDIR)))
 override IOS_TARGETDIR := $(patsubst %/,%,$(abspath $(IOS_TARGETDIR)))
 MONOTOUCH_PREFIX := $(abspath $(MONOTOUCH_PREFIX))
 
-MONOTOUCH_MONO_PATH?=$(abspath $(MONO_PATH)/mcs/class/lib/monotouch/)
-MONOTOUCH_TV_MONO_PATH?=$(abspath $(MONO_PATH)/mcs/class/lib/monotouch_tv/)
-MONOTOUCH_WATCH_MONO_PATH?=$(abspath $(MONO_PATH)/mcs/class/lib/monotouch_watch/)
+MONOTOUCH_MONO_PATH?=$(IOS_DESTDIR)$(MONOTOUCH_PREFIX)/lib/mono/Xamarin.iOS
+MONOTOUCH_TV_MONO_PATH?=$(IOS_DESTDIR)$(MONOTOUCH_PREFIX)/lib/mono/Xamarin.TVOS
+MONOTOUCH_WATCH_MONO_PATH?=$(IOS_DESTDIR)$(MONOTOUCH_PREFIX)/lib/mono/Xamarin.WatchOS
 
 IOS_PACKAGE_FILENAME=$(IOS_PACKAGE_NAME_LOWER)-$(IOS_PACKAGE_VERSION).pkg
 IOS_PACKAGE_UTI=com.xamarin.$(IOS_PACKAGE_NAME_LOWER).pkg
@@ -194,10 +194,8 @@ DEVICE_CC=$(IOS_CC)
 DEVICE_CXX=$(IOS_CXX)
 
 IOS_CSC=$(SYSTEM_CSC) -nostdlib -noconfig -r:$(MONOTOUCH_MONO_PATH)/System.dll -r:$(MONOTOUCH_MONO_PATH)/System.Core.dll -r:$(MONOTOUCH_MONO_PATH)/System.Xml.dll -r:$(MONOTOUCH_MONO_PATH)/mscorlib.dll -r:$(MONOTOUCH_MONO_PATH)/System.Net.Http.dll -r:$(MONOTOUCH_MONO_PATH)/Facades/System.Drawing.Common.dll -deterministic
-IOS_MCS=$(SYSTEM_MCS) -nostdlib -r:mscorlib.dll -lib:$(MONOTOUCH_MONO_PATH)
-
 TV_CSC=$(SYSTEM_CSC) -nostdlib -noconfig -r:$(MONOTOUCH_TV_MONO_PATH)/System.dll -r:$(MONOTOUCH_TV_MONO_PATH)/System.Core.dll -r:$(MONOTOUCH_TV_MONO_PATH)/System.Xml.dll -r:$(MONOTOUCH_TV_MONO_PATH)/mscorlib.dll -r:$(MONOTOUCH_TV_MONO_PATH)/System.Net.Http.dll -r:$(MONOTOUCH_TV_MONO_PATH)/Facades/System.Drawing.Common.dll -deterministic
-WATCH_CSC=$(SYSTEM_CSC) -nostdlib -noconfig -r:$(WATCH_BCL_DIR)/System.dll -r:$(WATCH_BCL_DIR)/System.Core.dll -r:$(WATCH_BCL_DIR)/System.Xml.dll -r:$(WATCH_BCL_DIR)/mscorlib.dll -r:$(WATCH_BCL_DIR)/System.Net.Http.dll -r:$(WATCH_BCL_DIR)/Facades/System.Drawing.Common.dll -deterministic
+WATCH_CSC=$(SYSTEM_CSC) -nostdlib -noconfig -r:$(MONOTOUCH_WATCH_MONO_PATH)/System.dll -r:$(MONOTOUCH_WATCH_MONO_PATH)/System.Core.dll -r:$(MONOTOUCH_WATCH_MONO_PATH)/System.Xml.dll -r:$(MONOTOUCH_WATCH_MONO_PATH)/mscorlib.dll -r:$(MONOTOUCH_WATCH_MONO_PATH)/System.Net.Http.dll -r:$(MONOTOUCH_WATCH_MONO_PATH)/Facades/System.Drawing.Common.dll -deterministic
 
 DEVICE_OBJC_CFLAGS=$(OBJC_CFLAGS) $(BITCODE_CFLAGS)
 
diff --git a/builds/Makefile b/builds/Makefile
index 6bd3a23d4a..8679435f96 100644
--- a/builds/Makefile
+++ b/builds/Makefile
@@ -150,7 +150,7 @@ $(MONO_PATH)/sdks/Make.config:
 ##
 
 # We only build the mono runtimes here (mac32 and mac64)
-# The xammac classlibs are built as a part of the 'tools64' build.
+# The xammac classlibs are built as a part of the 'bcl' build.
 
 MAC_ASSEMBLY_NAMES = \
 	I18N \
@@ -312,19 +312,17 @@ endef
 $(eval $(call MacBuildTemplate,i386,mac32,$(XCODE94_DEVELOPER_ROOT),32,$(XCODE94_MAC_SDKROOT)))
 $(eval $(call MacBuildTemplate,x86_64,mac64,$(XCODE_DEVELOPER_ROOT),,$(XCODE_MAC_SDKROOT)))
 
-$(MONO_PATH)/mcs/class/lib/%: .stamp-build-tools64;
-
 define MacInstallBclTemplate
 
 MAC_DIRECTORIES += \
-	$$(BUILD_DESTDIR)/bcl/$(2)/Facades \
-	$$(BUILD_DESTDIR)/bcl/$(2)         \
+	$$(BUILD_DESTDIR)/mac-bcl/$(2)/Facades \
+	$$(BUILD_DESTDIR)/mac-bcl/$(2)         \
 
-$$(MAC_DESTDIR)$$(MAC_FRAMEWORK_CURRENT_DIR)/lib/mono/$(1)/%: $$(BUILD_DESTDIR)/bcl/$(2)/% | $$(MAC_DESTDIR)$$(MAC_FRAMEWORK_CURRENT_DIR)/lib/mono/$(1)/Facades
+$$(MAC_DESTDIR)$$(MAC_FRAMEWORK_CURRENT_DIR)/lib/mono/$(1)/%: $$(BUILD_DESTDIR)/mac-bcl/$(2)/% | $$(MAC_DESTDIR)$$(MAC_FRAMEWORK_CURRENT_DIR)/lib/mono/$(1)/Facades
 	$$(Q) install -m 0755 $$< $$@
 
 
-$$(MAC_DESTDIR)$$(MAC_FRAMEWORK_CURRENT_DIR)/lib/mono/$(1)/%.pdb: $$(BUILD_DESTDIR)/mac/$(2)/bcl/%.pdb | $$(MAC_DESTDIR)$$(MAC_FRAMEWORK_CURRENT_DIR)/lib/mono/$(1)/Facades
+$$(MAC_DESTDIR)$$(MAC_FRAMEWORK_CURRENT_DIR)/lib/mono/$(1)/%.pdb: $$(BUILD_DESTDIR)/mac/$(2)/mac-bcl/%.pdb | $$(MAC_DESTDIR)$$(MAC_FRAMEWORK_CURRENT_DIR)/lib/mono/$(1)/Facades
 	$$(Q) install -m 0644 $$< $$@
 endef
 
@@ -337,8 +335,8 @@ $(MAC_DIRECTORIES) $(BUILD_DESTDIR):
 mac-facade-check: $(MAC_BCL_TARGETS)
 	$(Q) rm -f .$@*
 	$(Q) echo $(MAC_4_5_FACADE_ASSEMBLIES) | tr ' ' '\n' | sort > .$@1
-	$(Q) ls -1 $(MONO_PATH)/mcs/class/lib/xammac_net_4_5/Facades | grep dll$$ | sed 's/[.]dll//' | sort > .$@2
-	$(Q) if ! diff -u .$@1 .$@2; then echo "\n*** There are Facade assemblies in "$(MONO_PATH)/mcs/class/lib/xammac_net_4_5/Facades " not defined in "$(FACADE_SUBDIRS_MK)" ***\n"; exit 1; fi
+	$(Q) ls -1 $(MONO_MAC_SDK_DESTDIR)/mac-bcl/xammac_net_4_5/Facades | grep dll$$ | sed 's/[.]dll//' | sort > .$@2
+	$(Q) if ! diff -u .$@1 .$@2; then echo "\n*** There are Facade assemblies in "$(MONO_MAC_SDK_DESTDIR)/mac-bcl/xammac_net_4_5/Facades " not defined in "$(FACADE_SUBDIRS_MK)" ***\n"; exit 1; fi
 	$(Q) rm -f .$@*
 
 define lipo_template_static
@@ -456,81 +454,38 @@ $(IOS_DESTDIR)/$(MONOTOUCH_PREFIX)/bin/smcs:
 	@chmod +x $@
 
 #
-# Tools 64bit build.  Builds all the class libs as well.
+# BCL build.
 #
-TOOLS64_CFLAGS=-arch x86_64 -mmacosx-version-min=$(MIN_OSX_VERSION_FOR_MAC)
-TOOLS64_CXXFLAGS=-arch x86_64 -mmacosx-version-min=$(MIN_OSX_VERSION_FOR_MAC)
-TOOLS64_LDFLAGS=-arch x86_64 -mmacosx-version-min=$(MIN_OSX_VERSION_FOR_MAC) $(COMMON_LDFLAGS)
-
-TOOLS64_CONFIGURE_FLAGS=	--build=x86_64-apple-darwin10 \
-			--with-monotouch_tv=yes \
-			--with-monotouch_watch=yes \
-			--prefix=$(BUILD_DESTDIR)/tools64 \
-			--enable-maintainer-mode \
-			--cache-file=../tools64.config.cache \
-			--with-glib=embedded \
-			--enable-minimal=com	\
-			--with-profile4_x=no \
-			--with-monotouch=yes \
-			--with-xammac=yes \
-			--with-mcs-docs=no \
-			--disable-nls \
-			--disable-iconv	\
-			--disable-boehm \
-			$(XAMARIN_IOS_CONFIGURE_FLAGS) \
-
-TOOLS64_ACVARS = $(COMMON_ACVARS)
-
-TOOLS64_CONFIGURE_ENVIRONMENT = \
-	$(TOOLS64_ACVARS) \
-	CFLAGS="$(TOOLS64_CFLAGS)" \
-	CXXFLAGS="$(TOOLS64_CXXFLAGS)" \
-	LDFLAGS="$(TOOLS64_LDFLAGS)" \
-	DEVELOPER_DIR=$(XCODE_DEVELOPER_ROOT) \
-	CC="$(MAC_CC)" \
-	CXX="$(MAC_CXX)" \
-
-tools:: build-tools64 install-tools
-
-setup:: setup-tools64
-build:: build-tools64
-clean-local:: clean-tools64
-
-tools64: build-tools64 install-tools
 
 ifdef INCLUDE_IOS
-install-local:: install-tools-ios
-install-tools:: install-tools-ios
+install-bcl:: install-bcl-ios
 endif
-install-local:: install-tools-mac
-install-tools:: install-tools-mac
-
-setup-tools64: .stamp-configure-tools64
-
-.stamp-configure-tools64: $(MONO_PATH)/configure
-	$(Q) $(TOOLS64_CONFIGURE_ENVIRONMENT) ./wrap-configure.sh tools64 $(abspath $(MONO_PATH)/configure) $(TOOLS64_CONFIGURE_FLAGS)
-
-build-tools-bcl: build-tools64
-build-tools: build-tools64
-
-.stamp-build-tools64: .stamp-configure-tools64 $(MONO_DEPENDENCIES)
-	$(MAKE) -C tools64 all EXTERNAL_MCS=$(SYSTEM_CSC) EXTERNAL_RUNTIME=$(SYSTEM_MONO) MONOTOUCH_MCS_FLAGS=$(IOS_CSC_FLAGS) XAMMAC_MCS_FLAGS=$(MAC_CSC_FLAGS)
-	# NO_INSTALL is defined in mono/mcs/build/profiles except for net_4_5. If we don't have it, then it attempts to install into a gac, and sometimes fail
-	NO_INSTALL=1 $(MAKE) -C tools64 -j 1 install EXTERNAL_MCS=$(SYSTEM_CSC) EXTERNAL_RUNTIME=$(SYSTEM_MONO)
-	@touch .stamp-build-tools64
-
-clean-tools64:
-	rm -rf tools64 .stamp-*-tools64 tools64.config.cache
-	rm -f .stamp-build-tools64
-
 ifdef INCLUDE_WATCH
-install-local:: install-tools-watch
-install-tools:: install-tools-watch
+install-bcl:: install-bcl-watch
 endif
 ifdef INCLUDE_TVOS
-install-local:: install-tools-tvos
-install-tools:: install-tools-tvos
+install-bcl:: install-bcl-tvos
 endif
+# We need the mac libraries for mlaunch, so this can't be disabled
+install-bcl:: install-bcl-mac
+
+.stamp-compile-bcl: $(MONO_PATH)/configure $(SDK_CONFIG) $(MONO_DEPENDENCIES)
+	$(MAKE) -C $(SDK_BUILDDIR) package-ios-bcl package-mac-bcl $(SDK_ARGS)
+	$(Q) touch $@
+
+.stamp-build-bcl: .stamp-$(MONO_BUILD_MODE)-bcl;
+
+$(MONO_IOS_SDK_DESTDIR)/ios-bcl/%: .stamp-build-bcl;
+$(MONO_MAC_SDK_DESTDIR)/mac-bcl/%: .stamp-build-bcl;
+
+clean-bcl:
+	$(Q) rm -rf .stamp-*-bcl
+
+build:: build-bcl
+clean-local:: clean-bcl
+install-local:: install-bcl
+all-local:: install-bcl
+bcl: install-bcl
 
 #
 # Xamarin.iOS/WatchOS/TVOS BCL assemblies
@@ -560,27 +515,6 @@ WATCHOS_FACADE_ASSEMBLIES = $(IOS_FACADE_ASSEMBLIES)
 TVOS_REPL_ASSEMBLIES = $(IOS_REPL_ASSEMBLIES)
 WATCHOS_REPL_ASSEMBLIES = $(IOS_REPL_ASSEMBLIES)
 
-ios-facade-check: $(IOS_BCL_TARGETS)
-	$(Q) rm -f .$@*
-	$(Q) echo $(IOS_FACADE_ASSEMBLIES) | tr ' ' '\n' | sort > .$@1
-	$(Q) ls -1 $(MONO_PATH)/mcs/class/lib/monotouch/Facades | grep dll$$ | sed 's/[.]dll//' | sort > .$@2
-	$(Q) if ! diff -u .$@1 .$@2; then echo "\n*** There are Facade assemblies in "$(MONO_PATH)/mcs/class/lib/monotouch/Facades" not defined in "$(FACADE_SUBDIRS_MK)"***\n"; exit 1; fi
-	$(Q) rm -f .$@*
-
-watch-facade-check: $(WATCH_BCL_TARGETS)
-	$(Q) rm -f .$@*
-	$(Q) echo $(WATCHOS_FACADE_ASSEMBLIES) | tr ' ' '\n' | sort > .$@1
-	$(Q) ls -1 $(MONO_PATH)/mcs/class/lib/monotouch_watch/Facades | grep dll$$ | sed 's/[.]dll//' | sort > .$@2
-	$(Q) if ! diff -u .$@1 .$@2; then echo "\n*** There are Facade assemblies in "$(MONO_PATH)/mcs/class/lib/monotouch_watch/Facades" not defined in "$(FACADE_SUBDIRS_MK)" ***\n"; exit 1; fi
-	$(Q) rm -f .$@*
-
-tvos-facade-check: $(TVOS_BCL_TARGETS) 
-	$(Q) rm -f .$@*
-	$(Q) echo $(TVOS_FACADE_ASSEMBLIES) | tr ' ' '\n' | sort > .$@1
-	$(Q) ls -1 $(MONO_PATH)/mcs/class/lib/monotouch_tv/Facades | grep dll$$ | sed 's/[.]dll//' | sort > .$@2
-	$(Q) if ! diff -u .$@1 .$@2; then echo "\n*** There are Facade assemblies in "$(MONO_PATH)/mcs/class/lib/monotouch_tv/Facades" not defined in "$(FACADE_SUBDIRS_MK)" ***\n"; exit 1; fi
-	$(Q) rm -f .$@*
-
 NO_MDB_ASSEMBLIES = System.Windows System.Xml.Serialization
 
 IOS_BCL_TARGETS_DIRS +=                    \
@@ -590,33 +524,31 @@ IOS_BCL_TARGETS_DIRS +=                    \
 	$(PREFIX)/lib/mono/Xamarin.iOS/Facades \
 	$(PREFIX)/lib/mono/2.1/repl            \
 	$(PREFIX)/lib/mono/Xamarin.iOS/repl    \
-	$(BUILD_DESTDIR)/bcl/monotouch         \
-	$(BUILD_DESTDIR)/bcl/monotouch/Facades \
-	$(BUILD_DESTDIR)/bcl/monotouch_runtime \
+	$(BUILD_DESTDIR)/ios-bcl/monotouch         \
+	$(BUILD_DESTDIR)/ios-bcl/monotouch/Facades \
+	$(BUILD_DESTDIR)/ios-bcl/monotouch_runtime \
 
 WATCH_BCL_TARGETS_DIRS +=                      \
 	$(PREFIX)/lib/mono/Xamarin.WatchOS         \
 	$(PREFIX)/lib/mono/Xamarin.WatchOS/Facades \
 	$(PREFIX)/lib/mono/Xamarin.WatchOS/repl    \
-	$(BUILD_DESTDIR)/bcl/monotouch_watch         \
-	$(BUILD_DESTDIR)/bcl/monotouch_watch/Facades \
-	$(BUILD_DESTDIR)/bcl/monotouch_watch_runtime \
+	$(BUILD_DESTDIR)/ios-bcl/monotouch_watch         \
+	$(BUILD_DESTDIR)/ios-bcl/monotouch_watch/Facades \
+	$(BUILD_DESTDIR)/ios-bcl/monotouch_watch_runtime \
 
 TVOS_BCL_TARGETS_DIRS +=                    \
 	$(PREFIX)/lib/mono/Xamarin.TVOS         \
 	$(PREFIX)/lib/mono/Xamarin.TVOS/Facades \
 	$(PREFIX)/lib/mono/Xamarin.TVOS/repl    \
-	$(BUILD_DESTDIR)/bcl/monotouch_tv         \
-	$(BUILD_DESTDIR)/bcl/monotouch_tv/Facades \
-	$(BUILD_DESTDIR)/bcl/monotouch_tv_runtime \
+	$(BUILD_DESTDIR)/ios-bcl/monotouch_tv         \
+	$(BUILD_DESTDIR)/ios-bcl/monotouch_tv/Facades \
+	$(BUILD_DESTDIR)/ios-bcl/monotouch_tv_runtime \
 
 IOS_BCL_TARGETS +=                                                                                                  \
 	$(foreach file,$(IOS_ASSEMBLIES),$(PREFIX)/lib/mono/2.1/$(file).dll)                                                \
 	$(foreach file,$(filter-out $(NO_MDB_ASSEMBLIES),$(IOS_ASSEMBLIES)),$(PREFIX)/lib/mono/2.1/$(file).pdb)         \
 	$(foreach file,$(IOS_ASSEMBLIES),$(PREFIX)/lib/mono/Xamarin.iOS/$(file).dll)                                        \
 	$(foreach file,$(filter-out $(NO_MDB_ASSEMBLIES),$(IOS_ASSEMBLIES)),$(PREFIX)/lib/mono/Xamarin.iOS/$(file).pdb) \
-	$(PREFIX)/lib/mono/Xamarin.iOS/mscorlib.dll                                                                     \
-	$(PREFIX)/lib/mono/2.1/mscorlib.dll                                                                             \
 	$(foreach file,$(IOS_FACADE_ASSEMBLIES),$(PREFIX)/lib/mono/2.1/Facades/$(file).dll)                                 \
 	$(foreach file,$(IOS_FACADE_ASSEMBLIES),$(PREFIX)/lib/mono/Xamarin.iOS/Facades/$(file).dll)                         \
 	$(foreach file,$(IOS_REPL_ASSEMBLIES),$(PREFIX)/lib/mono/2.1/repl/$(file).dll)                                      \
@@ -627,7 +559,6 @@ IOS_BCL_TARGETS +=
 WATCH_BCL_TARGETS += \
 	$(foreach file,$(WATCHOS_ASSEMBLIES),$(PREFIX)/lib/mono/Xamarin.WatchOS/$(file).dll)                                        \
 	$(foreach file,$(filter-out $(NO_MDB_ASSEMBLIES),$(WATCHOS_ASSEMBLIES)),$(PREFIX)/lib/mono/Xamarin.WatchOS/$(file).pdb) \
-	$(PREFIX)/lib/mono/Xamarin.WatchOS/mscorlib.dll                                                                             \
 	$(foreach file,$(WATCHOS_FACADE_ASSEMBLIES),$(PREFIX)/lib/mono/Xamarin.WatchOS/Facades/$(file).dll)                         \
 	$(foreach file,$(WATCHOS_REPL_ASSEMBLIES),$(PREFIX)/lib/mono/Xamarin.WatchOS/repl/$(file).dll)                              \
 	$(foreach file,$(WATCHOS_REPL_ASSEMBLIES),$(PREFIX)/lib/mono/Xamarin.WatchOS/repl/$(file).pdb)                          \
@@ -635,88 +566,109 @@ WATCH_BCL_TARGETS += \
 TVOS_BCL_TARGETS += \
 	$(foreach file,$(TVOS_ASSEMBLIES),$(PREFIX)/lib/mono/Xamarin.TVOS/$(file).dll)                                        \
 	$(foreach file,$(filter-out $(NO_MDB_ASSEMBLIES),$(TVOS_ASSEMBLIES)),$(PREFIX)/lib/mono/Xamarin.TVOS/$(file).pdb) \
-	$(PREFIX)/lib/mono/Xamarin.TVOS/mscorlib.dll                                                                          \
 	$(foreach file,$(TVOS_FACADE_ASSEMBLIES),$(PREFIX)/lib/mono/Xamarin.TVOS/Facades/$(file).dll)                         \
 	$(foreach file,$(TVOS_REPL_ASSEMBLIES),$(PREFIX)/lib/mono/Xamarin.TVOS/repl/$(file).dll)                              \
 	$(foreach file,$(TVOS_REPL_ASSEMBLIES),$(PREFIX)/lib/mono/Xamarin.TVOS/repl/$(file).pdb)                          \
 
-$(PREFIX)/lib/mono/Xamarin.iOS/repl/%: $(BUILD_DESTDIR)/bcl/monotouch_runtime/% | $(PREFIX)/lib/mono/Xamarin.iOS/repl
+$(PREFIX)/lib/mono/Xamarin.iOS/repl/%: $(BUILD_DESTDIR)/ios-bcl/monotouch_runtime/% | $(PREFIX)/lib/mono/Xamarin.iOS/repl
 	$(Q) install -m 0755 $< $@
 
-$(PREFIX)/lib/mono/Xamarin.iOS/%: $(BUILD_DESTDIR)/bcl/monotouch/% | $(PREFIX)/lib/mono/Xamarin.iOS $(PREFIX)/lib/mono/Xamarin.iOS/Facades
+$(PREFIX)/lib/mono/Xamarin.iOS/%: $(BUILD_DESTDIR)/ios-bcl/monotouch/% | $(PREFIX)/lib/mono/Xamarin.iOS $(PREFIX)/lib/mono/Xamarin.iOS/Facades
 	$(Q) install -m 0644 $< $@
 
-$(PREFIX)/lib/mono/2.1/repl/%: $(BUILD_DESTDIR)/bcl/monotouch_runtime/% | $(PREFIX)/lib/mono/2.1/repl
+$(PREFIX)/lib/mono/2.1/repl/%: $(BUILD_DESTDIR)/ios-bcl/monotouch_runtime/% | $(PREFIX)/lib/mono/2.1/repl
 	$(Q) install -m 0755 $< $@
 
-$(PREFIX)/lib/mono/2.1/%: $(BUILD_DESTDIR)/bcl/monotouch/% | $(PREFIX)/lib/mono/2.1 $(PREFIX)/lib/mono/2.1/Facades
+$(PREFIX)/lib/mono/2.1/%: $(BUILD_DESTDIR)/ios-bcl/monotouch/% | $(PREFIX)/lib/mono/2.1 $(PREFIX)/lib/mono/2.1/Facades
 	$(Q) install -m 0755 $< $@
 
-$(PREFIX)/lib/mono/Xamarin.WatchOS/repl/%: $(BUILD_DESTDIR)/bcl/monotouch_watch_runtime/% | $(PREFIX)/lib/mono/Xamarin.WatchOS/repl
+$(PREFIX)/lib/mono/Xamarin.WatchOS/repl/%: $(BUILD_DESTDIR)/ios-bcl/monotouch_watch_runtime/% | $(PREFIX)/lib/mono/Xamarin.WatchOS/repl
 	$(Q) install -m 0755 $< $@
 
-$(PREFIX)/lib/mono/Xamarin.WatchOS/%: $(BUILD_DESTDIR)/bcl/monotouch_watch/% | $(PREFIX)/lib/mono/Xamarin.WatchOS $(PREFIX)/lib/mono/Xamarin.WatchOS/Facades
+$(PREFIX)/lib/mono/Xamarin.WatchOS/%: $(BUILD_DESTDIR)/ios-bcl/monotouch_watch/% | $(PREFIX)/lib/mono/Xamarin.WatchOS $(PREFIX)/lib/mono/Xamarin.WatchOS/Facades
 	$(Q) install -m 0755 $< $@
 
-$(PREFIX)/lib/mono/Xamarin.TVOS/repl/%: $(BUILD_DESTDIR)/bcl/monotouch_tv_runtime/% | $(PREFIX)/lib/mono/Xamarin.TVOS/repl
+$(PREFIX)/lib/mono/Xamarin.TVOS/repl/%: $(BUILD_DESTDIR)/ios-bcl/monotouch_tv_runtime/% | $(PREFIX)/lib/mono/Xamarin.TVOS/repl
 	$(Q) install -m 0755 $< $@
 
-$(PREFIX)/lib/mono/Xamarin.TVOS/%: $(BUILD_DESTDIR)/bcl/monotouch_tv/% | $(PREFIX)/lib/mono/Xamarin.TVOS $(PREFIX)/lib/mono/Xamarin.TVOS/Facades
+$(PREFIX)/lib/mono/Xamarin.TVOS/%: $(BUILD_DESTDIR)/ios-bcl/monotouch_tv/% | $(PREFIX)/lib/mono/Xamarin.TVOS $(PREFIX)/lib/mono/Xamarin.TVOS/Facades
 	$(Q) install -m 0755 $< $@
 
 # copy to temporary directory before signing
 # otherwise we end up re-signing if installing into a different directory.
 
 TMP_BCL_TARGET_DIRS = \
-	$(BUILD_DESTDIR)/bcl/monotouch \
-	$(BUILD_DESTDIR)/bcl/monotouch/Facades \
-	$(BUILD_DESTDIR)/bcl/monotouch_runtime \
-	$(BUILD_DESTDIR)/bcl/monotouch_tv \
-	$(BUILD_DESTDIR)/bcl/monotouch_tv/Facades \
-	$(BUILD_DESTDIR)/bcl/monotouch_tv_runtime \
-	$(BUILD_DESTDIR)/bcl/monotouch_watch \
-	$(BUILD_DESTDIR)/bcl/monotouch_watch/Facades \
-	$(BUILD_DESTDIR)/bcl/monotouch_watch_runtime \
-	$(BUILD_DESTDIR)/bcl/xammac \
-	$(BUILD_DESTDIR)/bcl/xammac/Facades \
-	$(BUILD_DESTDIR)/bcl/xammac_net_4_5 \
-	$(BUILD_DESTDIR)/bcl/xammac_net_4_5/Facades \
+	$(BUILD_DESTDIR)/ios-bcl/monotouch \
+	$(BUILD_DESTDIR)/ios-bcl/monotouch/Facades \
+	$(BUILD_DESTDIR)/ios-bcl/monotouch_runtime \
+	$(BUILD_DESTDIR)/ios-bcl/monotouch_tv \
+	$(BUILD_DESTDIR)/ios-bcl/monotouch_tv/Facades \
+	$(BUILD_DESTDIR)/ios-bcl/monotouch_tv_runtime \
+	$(BUILD_DESTDIR)/ios-bcl/monotouch_watch \
+	$(BUILD_DESTDIR)/ios-bcl/monotouch_watch/Facades \
+	$(BUILD_DESTDIR)/ios-bcl/monotouch_watch_runtime \
+	$(BUILD_DESTDIR)/mac-bcl/xammac \
+	$(BUILD_DESTDIR)/mac-bcl/xammac/Facades \
+	$(BUILD_DESTDIR)/mac-bcl/xammac_net_4_5 \
+	$(BUILD_DESTDIR)/mac-bcl/xammac_net_4_5/Facades \
 
-$(BUILD_DESTDIR)/bcl/%.dll: $(MONO_PATH)/mcs/class/lib/%.dll | $(TMP_BCL_TARGET_DIRS)
+$(BUILD_DESTDIR)/ios-bcl/%.dll: $(MONO_IOS_SDK_DESTDIR)/ios-bcl/%.dll | $(TMP_BCL_TARGET_DIRS)
 	$(Q) $(CP) $< $@
 	$(Q_SN) MONO_CFG_DIR=$(TOP) $(SYSTEM_SN) -q -R $@ $(PRODUCT_KEY_PATH)
 
-$(BUILD_DESTDIR)/bcl/%.pdb: $(MONO_PATH)/mcs/class/lib/%.pdb | $(TMP_BCL_TARGET_DIRS)
+$(BUILD_DESTDIR)/ios-bcl/%.pdb: $(MONO_IOS_SDK_DESTDIR)/ios-bcl/%.pdb | $(TMP_BCL_TARGET_DIRS)
+	$(Q) $(CP) $< $@
+
+$(BUILD_DESTDIR)/mac-bcl/%.dll: $(MONO_MAC_SDK_DESTDIR)/mac-bcl/%.dll | $(TMP_BCL_TARGET_DIRS)
+	$(Q) $(CP) $< $@
+	$(Q_SN) MONO_CFG_DIR=$(TOP) $(SYSTEM_SN) -q -R $@ $(PRODUCT_KEY_PATH)
+
+$(BUILD_DESTDIR)/mac-bcl/%.pdb: $(MONO_MAC_SDK_DESTDIR)/mac-bcl/%.pdb | $(TMP_BCL_TARGET_DIRS)
 	$(Q) $(CP) $< $@
 
 $(IOS_BCL_TARGETS_DIRS) $(WATCH_BCL_TARGETS_DIRS) $(TVOS_BCL_TARGETS_DIRS):
 	$(Q) mkdir -p $@
 
+ios-facade-check: $(IOS_BCL_TARGETS)
+	$(Q) rm -f .$@*
+	$(Q) echo $(IOS_FACADE_ASSEMBLIES) | tr ' ' '\n' | sort > .$@1
+	$(Q) ls -1 $(MONO_IOS_SDK_DESTDIR)/ios-bcl/monotouch/Facades | grep dll$$ | sed 's/[.]dll//' | sort > .$@2
+	$(Q) if ! diff -u .$@1 .$@2; then echo "\n*** There are Facade assemblies in "$(MONO_IOS_SDK_DESTDIR)/ios-bcl/monotouch/Facades" not defined in "$(FACADE_SUBDIRS_MK)"***\n"; exit 1; fi
+	$(Q) rm -f .$@*
+
+watch-facade-check: $(WATCH_BCL_TARGETS)
+	$(Q) rm -f .$@*
+	$(Q) echo $(WATCHOS_FACADE_ASSEMBLIES) | tr ' ' '\n' | sort > .$@1
+	$(Q) ls -1 $(MONO_IOS_SDK_DESTDIR)/ios-bcl/monotouch_watch/Facades | grep dll$$ | sed 's/[.]dll//' | sort > .$@2
+	$(Q) if ! diff -u .$@1 .$@2; then echo "\n*** There are Facade assemblies in "$(MONO_IOS_SDK_DESTDIR)/ios-bcl/monotouch_watch/Facades" not defined in "$(FACADE_SUBDIRS_MK)" ***\n"; exit 1; fi
+	$(Q) rm -f .$@*
+
+tvos-facade-check: $(TVOS_BCL_TARGETS) 
+	$(Q) rm -f .$@*
+	$(Q) echo $(TVOS_FACADE_ASSEMBLIES) | tr ' ' '\n' | sort > .$@1
+	$(Q) ls -1 $(MONO_IOS_SDK_DESTDIR)/ios-bcl/monotouch_tv/Facades | grep dll$$ | sed 's/[.]dll//' | sort > .$@2
+	$(Q) if ! diff -u .$@1 .$@2; then echo "\n*** There are Facade assemblies in "$(MONO_IOS_SDK_DESTDIR)/ios-bcl/monotouch_tv/Facades" not defined in "$(FACADE_SUBDIRS_MK)" ***\n"; exit 1; fi
+	$(Q) rm -f .$@*
+
 # Keep all intermediate files always.
 .SECONDARY:
 
-install-tools-tvos: $(TVOS_BCL_TARGETS) tvos-facade-check
-install-tools-watch: $(WATCH_BCL_TARGETS) watch-facade-check
-install-tools-ios: $(IOS_BCL_TARGETS) ios-facade-check
-install-tools-mac: $(MAC_BCL_TARGETS) mac-facade-check
-build-watchbcl: $(WATCH_BCL_TARGETS)
-
-$(IOS_BCL_TARGETS): .stamp-build-tools64
-$(TVOS_BCL_TARGETS): .stamp-build-tools64
-$(MAC_BCL_TARGETS): .stamp-build-tools64
-$(WATCH_BCL_TARGETS): .stamp-build-tools64
+install-bcl-tvos: $(TVOS_BCL_TARGETS) tvos-facade-check
+install-bcl-watch: $(WATCH_BCL_TARGETS) watch-facade-check
+install-bcl-ios: $(IOS_BCL_TARGETS) ios-facade-check
+install-bcl-mac: $(MAC_BCL_TARGETS) mac-facade-check
 
 ifdef INCLUDE_IOS
-build-tools64: $(IOS_BCL_TARGETS)
+build-bcl: $(IOS_BCL_TARGETS)
 endif
 ifdef INCLUDE_TVOS
-build-tools64: $(TVOS_BCL_TARGETS)
+build-bcl: $(TVOS_BCL_TARGETS)
 endif
 ifdef INCLUDE_WATCH
-build-tools64: $(WATCH_BCL_TARGETS)
+build-bcl: $(WATCH_BCL_TARGETS)
 endif
 
-build-tools64: $(MAC_BCL_TARGETS)
+build-bcl: $(MAC_BCL_TARGETS)
 
 verify-signature:
 	for file in $(PREFIX)/lib/mono/2.1/*.dll; do \
diff --git a/src/Makefile b/src/Makefile
index 5b4abd69d4..9f561d37b3 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -115,7 +115,6 @@ $(BUILD_DIR)/ios.rsp: Makefile Makefile.generator frameworks.sources
 		-tmpdir=$(IOS_BUILD_DIR)/native \
 		-baselib=$(IOS_BUILD_DIR)/native/core.dll \
 		-attributelib=$(IOS_BUILD_DIR)/native/Xamarin.iOS.BindingAttributes.dll \
-		-r=$(MONO_PATH)/mcs/class/lib/monotouch/System.dll \
 		-native-exception-marshalling \
 		--ns=ObjCRuntime \
 		--target-framework=Xamarin.iOS,v1.0 \
@@ -176,10 +175,10 @@ $(IOS_BUILD_DIR)/reference/Xamarin.iOS.dll: $(IOS_BUILD_DIR)/native-64/Xamarin.i
 $(IOS_BUILD_DIR)/reference/Xamarin.iOS.pdb: $(IOS_BUILD_DIR)/native-64/Xamarin.iOS.pdb | $(IOS_BUILD_DIR)/reference
 	$(Q) $(CP) $< $@
 
-$(IOS_DESTDIR)$(MONOTOUCH_PREFIX)/lib/mono/2.1/% : $(MACIOS_BINARIES_PATH)/% | $(IOS_DESTDIR)$(MONOTOUCH_PREFIX)/lib/mono/2.1
+$(IOS_DESTDIR)$(MONOTOUCH_PREFIX)/lib/mono/2.1/% : $(MACIOS_BINARIES_PATH)/% | $(IOS_DESTDIR)$(MONOTOUCH_PREFIX)/lib/mono/2.1 $(IOS_DESTDIR)$(MONOTOUCH_PREFIX)/lib/mono/2.1/Facades
 	$(Q) $(CP) $< $@
 
-$(IOS_DESTDIR)$(MONOTOUCH_PREFIX)/lib/mono/2.1/Facades/% : $(MACIOS_BINARIES_PATH)/Facades/% | $(IOS_DESTDIR)$(MONOTOUCH_PREFIX)/lib/mono/2.1
+$(IOS_DESTDIR)$(MONOTOUCH_PREFIX)/lib/mono/2.1/Facades/% : $(MACIOS_BINARIES_PATH)/Facades/% | $(IOS_DESTDIR)$(MONOTOUCH_PREFIX)/lib/mono/2.1/Facades
 	$(Q) $(CP) $< $@
 
 $(IOS_BUILD_DIR)/compat/%: $(MACIOS_BINARIES_PATH)/% | $(IOS_BUILD_DIR)/compat
@@ -201,6 +200,7 @@ IOS_TARGETS_DIRS += \
 	$(IOS_DESTDIR)$(MONOTOUCH_PREFIX)/lib/32bits               \
 	$(IOS_DESTDIR)$(MONOTOUCH_PREFIX)/lib/64bits               \
 	$(IOS_DESTDIR)$(MONOTOUCH_PREFIX)/lib/mono/2.1             \
+	$(IOS_DESTDIR)$(MONOTOUCH_PREFIX)/lib/mono/2.1/Facades     \
 
 IOS_TARGETS += \
 	$(PROJECT_DIR)/xamios.csproj                                                   \
@@ -575,7 +575,6 @@ WATCH_BMONO = MONO_PATH=$(WATCH_LIBDIR)/repl $(IOS_DESTDIR)$(MONOTOUCH_PREFIX)/b
 WATCH_GENERATOR=$(BUILD_DIR)/common/bgen.exe
 WATCH_GENERATE=$(SYSTEM_MONO) --debug $(WATCH_GENERATOR)
 WATCH_GENERATED_DEFINES= -d:WATCH -d:XAMCORE_3_0 -d:XAMCORE_2_0 -d:__UNIFIED__
-WATCH_BCL_DIR = $(MONO_PATH)/mcs/class/lib/monotouch_watch
 
 WATCHOS_EXTRA_CORE_SOURCES = \
     $(WATCH_BUILD_DIR)/Constants.cs    \
@@ -641,7 +640,6 @@ $(BUILD_DIR)/watchos.rsp: Makefile Makefile.generator frameworks.sources
 		-tmpdir=$(WATCH_BUILD_DIR)/watch                         \
 		-baselib=$(WATCH_BUILD_DIR)/watch/core.dll               \
 		-attributelib=$(WATCH_BUILD_DIR)/Xamarin.WatchOS.BindingAttributes.dll \
-		-r=$(MONO_PATH)/mcs/class/lib/monotouch_watch/System.dll \
 		-ns=MonoTouch.ObjCRuntime                                \
 		-native-exception-marshalling                            \
 		$(WATCH_GENERATED_DEFINES)				\
@@ -810,7 +808,6 @@ $(BUILD_DIR)/tvos.rsp: Makefile Makefile.generator frameworks.sources
 		-tmpdir=$(TVOS_BUILD_DIR)/tvos                         \
 		-baselib=$(TVOS_BUILD_DIR)/tvos/core.dll               \
 		-attributelib=$(TVOS_BUILD_DIR)/Xamarin.TVOS.BindingAttributes.dll \
-		-r=$(MONO_PATH)/mcs/class/lib/monotouch_tv/System.dll \
 		$(TVOS_GENERATED_DEFINES)				\
 		-ns=MonoTouch.ObjCRuntime                                \
 		-native-exception-marshalling                            \
diff --git a/src/OpenGLES/Makefile-1.0.include b/src/OpenGLES/Makefile-1.0.include
index 7f6a64b0c8..03a662f5e5 100644
--- a/src/OpenGLES/Makefile-1.0.include
+++ b/src/OpenGLES/Makefile-1.0.include
@@ -34,12 +34,12 @@ OPENTK_1_0_CSC_FLAGS = -warn:0 -unsafe -target:library -noconfig -publicsign -de
 # Xamarin.iOS
 
 $(IOS_BUILD_DIR)/reference/OpenTK-1.0%dll $(IOS_BUILD_DIR)/reference/OpenTK-1.0%pdb: $(IOS_BUILD_DIR)/reference/Xamarin.iOS.dll $(OPENTK_1_0_DEPENDENCIES) $(IOS_BUILD_DIR)/reference/OpenTK-1.0.dll.config
-	$(call Q_PROF_CSC,ios/unified) $(IOS_CSC) -nologo -r:$(MONOTOUCH_MONO_PATH)/System.dll -r:$(MONOTOUCH_MONO_PATH)/System.Xml.dll -r:$(MONOTOUCH_MONO_PATH)/Facades/System.Drawing.Common.dll $(OPENTK_1_0_CSC_FLAGS) -out:$(basename $@).dll -r:$< -D:XAMCORE_2_0
+	$(call Q_PROF_CSC,ios/unified) $(IOS_CSC) -nologo $(OPENTK_1_0_CSC_FLAGS) -out:$(basename $@).dll -r:$< -D:XAMCORE_2_0
 
 # Xamarin.TVOS
 
 $(TVOS_BUILD_DIR)/reference/OpenTK-1.0%dll $(TVOS_BUILD_DIR)/reference/OpenTK-1.0%pdb: $(TVOS_BUILD_DIR)/reference/Xamarin.TVOS.dll $(OPENTK_1_0_DEPENDENCIES) $(TVOS_BUILD_DIR)/reference/OpenTK-1.0.dll.config
-	$(call Q_PROF_CSC,tvos) $(SYSTEM_CSC) -nologo $(OPENTK_1_0_CSC_FLAGS) -r:$(TVOS_LIBDIR)/System.dll -r:$(TVOS_LIBDIR)/System.Xml.dll -r:$(TVOS_LIBDIR)/Facades/System.Drawing.Common.dll -out:$(basename $@).dll -r:$< -D:XAMCORE_2_0 -D:XAMCORE_3_0 -D:TVOS
+	$(call Q_PROF_CSC,tvos) $(TV_CSC) -nologo $(OPENTK_1_0_CSC_FLAGS) -out:$(basename $@).dll -r:$< -D:XAMCORE_2_0 -D:XAMCORE_3_0 -D:TVOS
 
 # common targets