I don't think these are practical limitations, more like limitations to be able to sell laptops and desktops. If we told intel that they could burn up to 350wa

I don't think these are practical limitations, more like limitations to be able to sell laptops and desktops. If we told intel that they could burn up to 350watts on the CPU and a 25lbs heatsink was acceptable, we'd probably have 10ghz processors. Problem is, there isn't a large market for that. Home users don't want a big ugly and noisy box and server buyers would prefer power and heat savings. Supercomputers just tie all this stuff together instead of creating some monster single-core. Actually, this was the strategy with the pentium 4. It was a fast and power hungry single-core. Turns out, efficiency per cycle and multicore are just superior solutions.