What is the reason that ARM based CPUs (for mobile devices) are more power saving than x86 CPUs?

Question

More specifically, is ARM architecture itself responsible for ARM based CPUs consuming less power, or are x86 based CPUs (for mobile devices) more power hungry only because nobody (Intel and others) has made them power saving yet?

So is the architecutre (ISA etc) itself responsible for power saving, or is there some other reason?

Answer 1

ARM chips are simple by comparison to x86 chips. Simple means less circuitry and less power. If you look at ARM assembler and 586 assembler you will see what I mean.

ARM chips have general purpose registers that you can apply simple operations to. x86 chips have registers of differing widths with specific uses (arithmetic, addressing) that you can do quite complex instructions with.

Answer 2

As said, ARM stands Advanced RISC Machine, the brand is bought up by Intel itself and a mobile tune up of it by Intel is called XScale.

I hazard to guess Intel itself found ARM due to its RISC heritage easier to tune than x86 of CISC ancestry.

Answer 3

They're explicitly designed for low power consumption, pure and simple. That also equates to lower performance in most cases as the two primary means of reducing power consumption are to lower clock speeds and cut the number of transistors on the die.