diff -up OpenImageIO-oiio-1fa4a20/src/include/thread.h.ppckh OpenImageIO-oiio-1fa4a20/src/include/thread.h
--- OpenImageIO-oiio-1fa4a20/src/include/thread.h.ppckh	2012-04-25 15:29:32.530321567 +0200
+++ OpenImageIO-oiio-1fa4a20/src/include/thread.h	2012-04-25 15:29:42.490320642 +0200
@@ -267,6 +267,11 @@ atomic_exchange_and_add (volatile int *a
 #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
@@ -292,6 +297,11 @@ atomic_exchange_and_add (volatile long l
 #  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
@@ -317,6 +327,8 @@ atomic_compare_and_exchange (volatile in
     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
@@ -336,6 +348,8 @@ atomic_compare_and_exchange (volatile lo
     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