[thesz]

You are not quite right, to put it mildly.

The real problem is energy efficiency, it shows its head everywhere, from embedded systems and tablets to supercomputers. Even desktops are affected - you can cut cost of machine by having less costly power supply.

Most of the time you are not constrained by information stored in instruction cache for RISC CPUs, because most of time is being spent in some tight loop. And you can see how hard it is to create an energy efficient implementation for x86, partially (and in noticeable part) because x86 decoder is complex.