The only thing AMD proved is that you could glue 64-bit operands onto a 32-bit processor and that people cared more about running their old software slightly faster than running future software much faster. Thanks to AMD, we're still stuck with one of the first and worst CPU architectures imaginable. The only reason x86/x64 can outperform competitors is due to huge research budgets pushed into eaking out increasingly smaller improvements. It required an entirely new market to give ARM the inroads it needed to start throwing around large research budgets too. I suspect at some point ARM will move onto the desktop (Microsoft-willing) and then Intel can finally start retiring their x86-limited CPU.