diff --git a/README b/README
index 31e249e..3b08c84 100644
--- a/README
+++ b/README
@@ -20,7 +20,7 @@ make it so Syn68k builds on a few more platforms than it did.  There's
 still a lot of cruft that can be removed and still a bunch of gotchas
 that require special command line arguments to the configuration
 utility, but at least there are enough variants that can be built to
-show that both big-endian (e.g., PPC) and little-endian (e.g. i386, x86_64),
+show that both big-endian (e.g., PowerPC) and little-endian (e.g. i386, x86_64),
 32-bit and 64-bit, native (i386-only) and non-native versions work.
 
 On i386 Fedora systems (tested on 9 and 11), this version of Syn68k
@@ -51,9 +51,10 @@ currently have to override the cleanup script, since the stock script
   make
   make install        
 
-To compile syn68k on PPC Mac OS X (tested under 10.5.7), you must explicitly
-request the non-native port (the default is to try to build the native
-backend even on architectures where it's not supported--bad default!)
+To compile syn68k on PowerPC Mac OS X (tested under 10.5.7), you must
+explicitly request the non-native port (the default is to try to build
+the native backend even on architectures where it's not supported--bad
+default!)
 
   ./autogen.sh
   ./configure --disable-native
diff --git a/TODO b/TODO
index ac17fda..fde95e0 100644
--- a/TODO
+++ b/TODO
@@ -1,12 +1,15 @@
-        --enable-native should only be present where it's available
-        and perhaps should default to whatever is fastest (e.g., I
-        believe it's faster to run native in 32-bit mode on an x86_64
-        than it is to run non-native in 64-bit mode on an x86_64, although
-        I haven't yet timed them)
+        cleanup and optimize shouldn't be done via environment variables;
+        they should be done with AC_ARG_ENABLE and default to be turned on
+        on the architectures where they work (and should be made to work on
+        the architectures they support)
 
         only invoke the x86 cleanup & optimize when compiling for an
         x86 architecture
 
+                can probably write cleanup scripts for other architectures,
+                don't think it's worth doing optimize though (which may no
+                longer be a good idea w/ newer compilers)
+
         Fix i486-cleanup.pl and i486-optimize.pl for all x86 targets
         (including Mac OS X)
 
@@ -19,6 +22,9 @@
         	figure out *exactly* which options should be available
         	via configure
 
+        Not sure what we should do with x86_64 machines; need to know more
+        about what the popular distributions do
+
 	Figure out exactly which variables Makefile.common.in sets, then
 	get rid of Makefile.common.in
 
diff --git a/configure.ac b/configure.ac
index 59c3098..c328188 100644
--- a/configure.ac
+++ b/configure.ac
@@ -64,15 +64,26 @@ AC_SUBST(host_cpu_class)
 
 AC_ARG_ENABLE([native],
 	      AC_HELP_STRING([--enable-native],
-			     [native or nonnative (default is native)]),
-	      [var_native=$enable_native], [var_native=yes] )
-if test "$var_native" = "yes"; then
+			     [recompile into x86 code (default enabled for x86)]),
+	      [], [if test x$host_cpu_class = xi386; then
+                     enable_native=yes
+                   else
+                     enable_native=no
+                   fi])
+
+AC_MSG_CHECKING([native support])
+if test x$enable_native = xyes; then
+  if test x$host_cpu_class != xi386; then
+    AC_MSG_ERROR([Can't build native on non-x86])
+  fi
   HOST_NATIVE="native/i386"
   NONNATIVE=""
 else
   HOST_NATIVE="native/null"
   NONNATIVE="#define NONNATIVE"
 fi
+AC_MSG_RESULT([$enable_native])
+
 AC_SUBST(NONNATIVE)
 AC_SUBST(HOST_NATIVE)