diff --git a/configure/os/CONFIG_SITE.Common.darwin-ppc b/configure/os/CONFIG_SITE.Common.darwin-ppc
index 93a18bd4c..659ac782d 100644
--- a/configure/os/CONFIG_SITE.Common.darwin-ppc
+++ b/configure/os/CONFIG_SITE.Common.darwin-ppc
@@ -11,4 +11,5 @@
 #   ppc64   - Not tested
 
 ARCH_CLASS = ppc
+#ARCH_CLASS = ppc64
 #ARCH_CLASS = ppc ppc64
diff --git a/configure/os/CONFIG_SITE.Common.darwin-ppcx86 b/configure/os/CONFIG_SITE.Common.darwin-ppcx86
index 217046ef1..e4c32e968 100644
--- a/configure/os/CONFIG_SITE.Common.darwin-ppcx86
+++ b/configure/os/CONFIG_SITE.Common.darwin-ppcx86
@@ -10,9 +10,14 @@
 #   ppc
 #   i386
 #   ppc64   - Not tested
-#   x86_64  - Needs MacOS 10.5 or 10.4 with Universal SDK
+#   x86_64  - Needs MacOS 10.4 with Universal SDK, or 10.5 or later.
 
 ARCH_CLASS = ppc i386
+#ARCH_CLASS = ppc x86_64
 #ARCH_CLASS = ppc i386 x86_64
+#ARCH_CLASS = ppc64 i386
+#ARCH_CLASS = ppc64 x86_64
+#ARCH_CLASS = ppc64 i386 x86_64
 #ARCH_CLASS = ppc ppc64 i386
+#ARCH_CLASS = ppc ppc64 x86_64
 #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
index 9f7e806db..9f9e7887b 100644
--- a/configure/os/CONFIG_SITE.Common.darwin-x86
+++ b/configure/os/CONFIG_SITE.Common.darwin-x86
@@ -6,9 +6,10 @@
 # Site override definitions for darwin-x86 target builds
 #-------------------------------------------------------
 
-# Select which CPU architectures to include in your universal binaries:
+# Select which CPU architecture(s) to include in your MacOS binaries:
 #   i386
-#   x86_64  - Needs MacOS 10.5 or 10.4 with Universal SDK
+#   x86_64  - Needs MacOS 10.4 with the Universal SDK, or 10.5 and later
 
 ARCH_CLASS = i386
+#ARCH_CLASS = x86_64
 #ARCH_CLASS = i386 x86_64