There are a few other things that could also impact results. Looking at the experimental design, there could be a good 25% uncertainty in the results because of how it's done at such a high level.
Rough up-to values for various things I can think of / see:
- 10% because they're using an OS rather than running binaries straight.
- 15% because GCC is odd and -O3 does even stranger things, particularly when it comes to energy.
- 15% because their benchmarks are large workloads rather than microbenchmarks that may better target the architecture rather than being huge lumps (would exacerbate GCC strangeness).
- 17% because they're measuring board rather than CPU power supply (the claim that SoC-based ARM development boards cannot have processor power isolated is questionable - I've seen Beagleboards with the CPU power supply isolated)
- 10% because they're measuring energy consumption at a low resolution (their equipment measures in Hz when there's kit that happily measures in kHz or MHz).
Of course, some of these will cancel, and others will be nowhere near as bad as stated. It also doesn't introduce order-of-magnitude changes to the conclusions, although a few of the 'Key Findings' may want questioning.
Did anyone find a reasonably prominent link to the source?
It seems to me as if this article is mostly linkbait simply by reason of it failing to provide anything more than vague phrases about the source: "This paper is an updated version of one I’ve referenced in previous stories, ... the team from the University of Wisconsin"
Half-baked studies frequently attempt to shout down the real hard science.
Think we have the answer in the source article's abstract,
" Our methodical investigation demonstrates the role of ISA
in modern microprocessors’ performance and energy efficiency.
We find that ARM and x86 processors are simply engineering
design points optimized for different levels of performance, and
there is nothing fundamentally more energy efficient in one ISA
class or the other. The ISA being RISC or CISC seems irrelevant."
