diff -Naur OpenImageIO-oiio-2939154.orig/src/include/thread.h OpenImageIO-oiio-2939154/src/include/thread.h
--- OpenImageIO-oiio-2939154.orig/src/include/thread.h	2012-06-04 12:30:16.000000000 -0500
+++ OpenImageIO-oiio-2939154/src/include/thread.h	2012-06-13 15:14:36.648990016 -0500
@@ -103,7 +103,7 @@
 #endif
 
 #if defined(__GNUC__) && (defined(_GLIBCXX_ATOMIC_BUILTINS) || (__GNUC__ * 100 + __GNUC_MINOR__ >= 401))
-#if !defined(__FreeBSD__) || defined(__x86_64__)
+#if !defined(__FreeBSD__) && !defined(__PPC__) || defined(__x86_64__)
 #define USE_GCC_ATOMICS
 #endif
 #endif
@@ -272,6 +272,11 @@
 #elif defined(_WIN32)
     // Windows
     return _InterlockedExchangeAdd ((volatile LONG *)at, x);
+#elif defined (__PPC__)
+   long long r;
+   r = *at;
+   *at += x;
+   return r;
 #else
 #   error No atomics on this platform.
 #endif
@@ -297,6 +302,11 @@
 #  else
     return InterlockedExchangeAdd64 ((volatile LONGLONG *)at, x);
 #  endif
+#elif defined (__PPC__)
+   long long r;
+   r = *at;
+   *at += x;
+   return r;
 #else
 #   error No atomics on this platform.
 #endif
@@ -322,6 +332,8 @@
     return OSAtomicCompareAndSwap32Barrier (compareval, newval, at);
 #elif defined(_WIN32)
     return (_InterlockedCompareExchange ((volatile LONG *)at, newval, compareval) == compareval);
+#elif defined(__PPC__)
+    return ((*at == compareval) ? (*at = newval), 1 : 0);
 #else
 #   error No atomics on this platform.
 #endif
@@ -341,6 +353,8 @@
     return OSAtomicCompareAndSwap64Barrier (compareval, newval, at);
 #elif defined(_WIN32)
     return (_InterlockedCompareExchange64 ((volatile LONGLONG *)at, newval, compareval) == compareval);
+#elif defined(__PPC__)
+    return ((*at == compareval) ? (*at = newval), 1 : 0);
 #else
 #   error No atomics on this platform.
 #endif