This was interesting in 1995. By 2005-2010, SoCs included sophisticated cache architecture, memory controller, internal and external bus controller, transceivers, and maybe iGPU. All of which play a role in performance per watt. ISA was no longer preeminent. Plus, if you emulate multicore x86-64 with superscalar vliw scheduling you're still constrained by the memory model, too. There is only so much you can do.