And here we go again
Current A-series processors have enough raw power to somehow compete with 13" MBP. So, going back to my previous comment, you can scale this processor to reach the same TDP and then have a high-end CPU with enough power to do anything your CPU can.
x86 architecture is heavily overloaded with rudimentary instructions and it takes more time to perform the majority of the modern tasks than ARM that's much younger and has less unneeded stuff.
And again, Leopard is too old, but there are more difficulties with emulation than with the performing modern tasks on an ARM processor. Just to make it clear, A13 is 6W chip (according to some website I found on the internet
) and it's pretty powerful for anything you can imagine in terms of mobile tasks. When you go to the desktop performance with desktop-level cooling solutions, take this CPU, scale it to have much more transistors and cores so it matches your perfect high-end CPU. Even if it won't be as powerful (I doubt it wouldn't), you need to keep in mind that ARM is evolving with insane speed and in nearest future, I don't see a reason not to replace current architecture with a more modern one.
