diff --git a/configure/os/CONFIG.Common.darwin-ppc b/configure/os/CONFIG.Common.darwin-ppc
index 7ac7c8a01..b77530c30 100644
--- a/configure/os/CONFIG.Common.darwin-ppc
+++ b/configure/os/CONFIG.Common.darwin-ppc
@@ -8,9 +8,8 @@
 #-------------------------------------------------------
 
 #
-# Architecture-specific information
-#
-ARCH_CLASS = ppc
+# To build universal binaries, configure ARCH_CLASS
+# in the file CONFIG_SITE.Common.darwin-ppc
 
 # Include definitions common to all Darwin targets
 include $(CONFIG)/os/CONFIG.darwinCommon.darwinCommon
diff --git a/configure/os/CONFIG.Common.darwin-ppcx86 b/configure/os/CONFIG.Common.darwin-ppcx86
index 75c9cf3f6..43c2640f9 100644
--- a/configure/os/CONFIG.Common.darwin-ppcx86
+++ b/configure/os/CONFIG.Common.darwin-ppcx86
@@ -3,20 +3,13 @@
 # $Id$
 # This file is maintained by the build community.
 #
-# Definitions for Darwin 'universal' (PowerPC, Intel) target builds
+# Definitions for Darwin universal PowerPC + x86 target builds
 # Sites may override these definitions in CONFIG_SITE.Common.darwin-ppcx86
 #-------------------------------------------------------
 
 #
-# Set architecture-specific information
-#
-ARCH_CLASS = ppcx86
-
-#
-# Universal binary support
-#
-OP_SYS_CFLAGS += -arch i386 -arch ppc
-OP_SYS_LDFLAGS += -arch i386 -arch ppc
+# To build universal binaries, configure ARCH_CLASS
+# in the file CONFIG_SITE.Common.darwin-ppcx86
 
 # Include definitions common to all Darwin targets
 include $(CONFIG)/os/CONFIG.darwinCommon.darwinCommon
diff --git a/configure/os/CONFIG.Common.darwin-x86 b/configure/os/CONFIG.Common.darwin-x86
index e34dce1dd..834c33e5d 100644
--- a/configure/os/CONFIG.Common.darwin-x86
+++ b/configure/os/CONFIG.Common.darwin-x86
@@ -8,9 +8,8 @@
 #-------------------------------------------------------
 
 #
-# Architecture-specific information
-#
-ARCH_CLASS = x86
+# To build universal binaries, configure ARCH_CLASS
+# in the file CONFIG_SITE.Common.darwin-x86
 
 # Include definitions common to all Darwin targets
 include $(CONFIG)/os/CONFIG.darwinCommon.darwinCommon
diff --git a/configure/os/CONFIG.darwin-ppcx86.Common b/configure/os/CONFIG.darwin-ppcx86.Common
index 74bc37534..b0bce4f63 100644
--- a/configure/os/CONFIG.darwin-ppcx86.Common
+++ b/configure/os/CONFIG.darwin-ppcx86.Common
@@ -3,7 +3,7 @@
 # $Id$
 # This file is maintained by the build community.
 #
-# Definitions for Darwin 'universal' (PowerPC, Intel) host builds
+# Definitions for Darwin universal PowerPC + x86 host builds
 # Sites may override these definitions in CONFIG_SITE.darwin-ppcx86.Common
 #-------------------------------------------------------
 
diff --git a/configure/os/CONFIG.darwinCommon.darwinCommon b/configure/os/CONFIG.darwinCommon.darwinCommon
index e9b12d56c..e158518f3 100644
--- a/configure/os/CONFIG.darwinCommon.darwinCommon
+++ b/configure/os/CONFIG.darwinCommon.darwinCommon
@@ -3,8 +3,8 @@
 # $Id$
 # This file is maintained by the build community.
 #
-# Definitions for darwin target builds
-# Sites may override these definitions in CONFIG_SITE.Common.darwin-<arch>
+# Common definitions for darwin builds
+# Sites may override these definitions in CONFIG_SITE.darwinCommon.darwinCommon
 #-------------------------------------------------------
 
 # Include definitions common to all Unix targets
@@ -18,6 +18,18 @@ include $(CONFIG)/CONFIG.gnuCommon
 #
 OS_CLASS = Darwin
 
+#
+# Build architecture flags
+#   For Darwin, ARCH_CLASS may be empty, or may contain a list of CPU
+#   architectures which must be valid arguments to the -arch options
+#   for the cc and ld commands.
+#   ARCH_CLASS is defined in a CONFIG_SITE file which is not loaded
+#   until after this file.
+#
+ARCH_DEP_FLAGS = $(addprefix -arch ,$(ARCH_CLASS))
+ARCH_DEP_CFLAGS += $(ARCH_DEP_FLAGS)
+ARCH_DEP_LDFLAGS += $(ARCH_DEP_FLAGS)
+
 #
 # Special flags for Darwin
 #   No common blocks (as required when using shared libraries)
diff --git a/configure/os/CONFIG_SITE.Common.darwin-ppc b/configure/os/CONFIG_SITE.Common.darwin-ppc
new file mode 100644
index 000000000..45fceee82
--- /dev/null
+++ b/configure/os/CONFIG_SITE.Common.darwin-ppc
@@ -0,0 +1,14 @@
+# CONFIG_SITE.Common.darwin-ppc
+#
+# $Id$
+# This file is maintained by the build community.
+#
+# Site override definitions for darwin-ppc target builds
+#-------------------------------------------------------
+
+# Select which CPU architectures to include in your universal binaries:
+#   ppc
+#   ppc64   - Not tested
+
+ARCH_CLASS = ppc
+#ARCH_CLASS = ppc ppc64
diff --git a/configure/os/CONFIG_SITE.Common.darwin-ppcx86 b/configure/os/CONFIG_SITE.Common.darwin-ppcx86
new file mode 100644
index 000000000..670526233
--- /dev/null
+++ b/configure/os/CONFIG_SITE.Common.darwin-ppcx86
@@ -0,0 +1,18 @@
+# CONFIG_SITE.Common.darwin-ppcx86
+#
+# $Id$
+# This file is maintained by the build community.
+#
+# Site override definitions for darwin-ppcx86 target builds
+#----------------------------------------------------------
+
+# Select which CPU architectures to include in your universal binaries:
+#   ppc
+#   i386
+#   ppc64   - Not tested
+#   x86_64  - Needs MacOS 10.5 or 10.4 with Universal SDK
+
+ARCH_CLASS = ppc i386
+#ARCH_CLASS = ppc i386 x86_64
+#ARCH_CLASS = ppc ppc64 i386
+#ARCH_CLASS = ppc ppc64 i386 x86_64
diff --git a/configure/os/CONFIG_SITE.Common.darwin-x86 b/configure/os/CONFIG_SITE.Common.darwin-x86
new file mode 100644
index 000000000..0b0b4e717
--- /dev/null
+++ b/configure/os/CONFIG_SITE.Common.darwin-x86
@@ -0,0 +1,14 @@
+# CONFIG_SITE.Common.darwin-x86
+#
+# $Id$
+# This file is maintained by the build community.
+#
+# Site override definitions for darwin-x86 target builds
+#-------------------------------------------------------
+
+# Select which CPU architectures to include in your universal binaries:
+#   i386
+#   x86_64  - Needs MacOS 10.5 or 10.4 with Universal SDK
+
+ARCH_CLASS = i386
+#ARCH_CLASS = i386 x86_64
diff --git a/configure/os/CONFIG_SITE.darwin-ppc.Common b/configure/os/CONFIG_SITE.darwin-ppc.Common
index 3bd24bc00..4639bd874 100644
--- a/configure/os/CONFIG_SITE.darwin-ppc.Common
+++ b/configure/os/CONFIG_SITE.darwin-ppc.Common
@@ -5,5 +5,3 @@
 #
 # Site override definitions for darwin-ppc host builds
 #-------------------------------------------------------
-
-CROSS_COMPILER_TARGET_ARCHS = # RTEMS-uC5282 RTEMS-mvme5500  RTEMS-mvme2100
diff --git a/configure/os/CONFIG_SITE.darwin-ppcx86.Common b/configure/os/CONFIG_SITE.darwin-ppcx86.Common
index 88249f6c0..e934383e7 100644
--- a/configure/os/CONFIG_SITE.darwin-ppcx86.Common
+++ b/configure/os/CONFIG_SITE.darwin-ppcx86.Common
@@ -5,8 +5,3 @@
 #
 # Site override definitions for darwin-ppcx86 host builds
 #-------------------------------------------------------
-
-#
-# Need this to get OS X readline rather than Fink (PPC-only) readline
-#
-OP_SYS_LDFLAGS +=  -L/usr/lib
diff --git a/configure/os/CONFIG_SITE.darwin-x86.Common b/configure/os/CONFIG_SITE.darwin-x86.Common
index 5d3e000d6..35c2157e4 100644
--- a/configure/os/CONFIG_SITE.darwin-x86.Common
+++ b/configure/os/CONFIG_SITE.darwin-x86.Common
@@ -1,9 +1,7 @@
-# CONFIG_SITE.darwin-ppc.Common
+# CONFIG_SITE.darwin-x86.Common
 #
 # $Id$
 # This file is maintained by the build community.
 #
-# Site override definitions for darwin-ppc host builds
+# Site override definitions for darwin-x86 host builds
 #-------------------------------------------------------
-
-CROSS_COMPILER_TARGET_ARCHS = # RTEMS-uC5282 # RTEMS-mvme5500  RTEMS-mvme2100