AMS: You demonstrate your lack of talent in this respect with your suggestions. Simply reordering/tuning/scheduling instructions to optimise for XScale does not render the code unable to execute on other CPUs. The only thing that does (and is what The Chox did) is to specifically ask the compiler to use instructions that only the XScale has. Why go to extra effort to make it more likely that bugs will occur at the same time as making it more difficult to debug, and limiting the number of users who can test it? Peter knows better than this, and also knows that there was no good technical reason to do so. So we're still left guessing as to why he chose to do it.