At first look, there would appear to be two substantial roadblocks to this happening. The first is simply performance. For computers (as opposed to iPads) per

At first look, there would appear to be two substantial roadblocks to this happening. The first is simply performance. For computers (as opposed to iPads) performance is king, and Intel is the undisputed champion of performance, at least at the moment. We would need to see substantial advances in performance by ARM manufacturers that we just aren't seeing yet - maybe NVidia has the capacity to make it happen? The second problem is that trying to take an application that runs on a powerful Intel chip, and then emulate the Intel instruction set on an ARM chip would be just diabolically slow. Apple have already changed the processor family twice for the Mac (68000->PowerPC, PowerPC->Intel), but in both cases the new architecture was substantially more powerful than the predecessor. That is not the case with a transition from Intel to ARM. Of course, this time around there is a potential game-changer, the Mac App Store. Applications built for the App Store are at least in theory very easy to rebuild for another CPU architecture, and then push to users. You have an app bought for your Intel Mac, you "upgrade" to an ARM Mac, and the App Store automatically grabs the ARM version of your software for you. Still, the two problems are showstoppers, each in its own right. Power has to improve substantially, and the Mac App Store needs to cement itself as the way to distribute software on the Mac before any such transition could be envisaged. Which is not to say that Apple doesn't already have a build of Mac OSX running on an ARM motherboard - indeed I would think it likely that they do have such a beast in the lab - but its purpose would be more as a bargaining chip with Intel, and as an interesting future direction, rather than as an actual product.