Twirrim: <i>ARM has typically been more efficient, for both heat and power consumption, while losing out on computational power.</i><p>i_have_to_speak : <i>Current ARM server chips are much worse than Intel chips on the performance&#x2F;watt metric.</i><p>It&#x27;s hard to square these two statements.  It might depend on how you define &quot;efficiency&quot;.  If efficiency is the amount of energy to perform a calculation, I don&#x27;t think ARM is more efficient.  This paper from a couple years ago concludes that ISA is no longer a defining factor: <a href="http:&#x2F;&#x2F;www.embedded.com&#x2F;design&#x2F;connectivity&#x2F;4436593&#x2F;Analysis-of-contemporary-ARM-and-x86-architectures" rel="nofollow">http:&#x2F;&#x2F;www.embedded.com&#x2F;design&#x2F;connectivity&#x2F;4436593&#x2F;Analysis...</a><p>Separately, this is an excellent article comparing recent generations of Intel against each other, showing that although power use has been going up, &quot;instructions per cycle&quot; has been going up even faster, resulting in a net improvement in energy efficiency: <a href="http:&#x2F;&#x2F;kentcz.com&#x2F;downloads&#x2F;P149-ISCA14-Preprint.pdf" rel="nofollow">http:&#x2F;&#x2F;kentcz.com&#x2F;downloads&#x2F;P149-ISCA14-Preprint.pdf</a>