zlacker

>>evolve+(OP)
Can someone tell me how much more power efficient is ARM actually? Like under load when gaming, not in a phone that sleeps most of the time. I've heard both claims, that it's still a huge difference and that for new AMD Zen it's basically the same.

>>Perz1v+y83
The instruction set has marginal impact. But many power efficient chips happen to be using the ARM instruction set today.

>>fulafe+Ye3
I think that's still highly debatable. Intel and AMD claim the instruction set makes no difference... but of course they would. And if that's really the case where are the power efficient x86 chips?

Possibly the truth is that everyone is talking past each other. Certainly in the Moore's Law days "marginal impact" would have meant maybe less then 20%, because differences smaller than that pretty much didn't matter. And there's no way the ISA makes 20% difference.

But today I'd say "marginal impact" is less than 5% which is way more debatable.

>>IshKeb+JN3
> And if that's really the case where are the power efficient x86 chips?

Where are the power inefficient x86 chips? If you normalize for production process and put the chips under synthetic load, ARM and x86 usually end up in a similar ballpark of efficiency. ARM is typically less efficient for wide SIMD/vector workloads, but more efficient at idle.

AMD and Intel aren't smartphone manufacturers. Their cash cows aren't in manufacturing mobile chipsets, and neither of them have sweetheart deals on ARM IP with Softbank like Apple does. For the markets they address, it's not unlikely that ARM would be both unprofitable and more power-hungry.

>>bigyab+KP3
Jim Keller goes into some detail about what difference the ISA makes in general in this clip https://youtu.be/yTMRGERZrQE?si=u-dEXwxp0MWPQumy

Spoiler, it's not much because most of the actual execution time is spent in a handful of basic OPs.

Branch prediction is where the magic happens today.

>>mhast+7U3
Jim Keller has to say that.