[bob1029]

> Across all workloads, energy consumption is proportional to execution time

Race-to-idle used to be the best path before multicore. Now it's trickier to determine how to clock the device. Especially in battery powered cases. This is why all modern CPU manufacturers are looking into heterogeneous compute (efficiency vs performance cores).

Put differently, I don't think we should be killing ourselves over this at software time. If you are actually concerned about the impact on raw energy consumption, you should move your workloads from AMD/Intel to ARM/Apple. Everything else would be noise compared to this.

[adrian_b]

Programs whose performance is dominated by array operations, as it is the case for most scientific/technical/engineering applications, achieve a much better energy efficiency on the AMD or Intel CPUs with good AVX-512 support, e.g. Zen 5 Ryzen or Epyc CPUs and Granite Rapids Xeons, than on almost all ARM-based CPUs, including on all Apple CPUs (the only ARM-based CPUs with good energy efficiency for such applications are made by Fujitsu, but they are unobtainium).

So if you want maximum energy efficiency, you should choose well your CPU, but a prejudice like believing that ARM-based CPUs are always better is guaranteed to lead to incorrect decisions.

The Apple CPUs have exceptional and unmatched energy efficiency in single-thread applications, but their energy efficiency in multi-threaded applications is not better than that of Intel/AMD CPUs made with the same TSMC CMOS fabrication process, so Apple can have only a temporary advantage, when they use first some process to which competitors do not have access.

Except for personal computers, the energy efficiency that matters is that of multi-threaded applications, so there Apple does not have anything to offer.

[adgjlsfhk1]

this is a very silly take. cpu isa is at most a 2x difference, and software has plenty of 100x differences. most of the difference between Windows and macos isn't the chips, OS and driver bloat is a much bigger factor

[adrian_b]

CPU ISA is at most a 2x difference for programs that use only the general-purpose registers and operations.

For applications that use vector or matrix operations and which may need some specific features, it is frequent to have a 4x to 10x better performance, or even more than this, when passing from a badly-designed ISA to a well-designed ISA, e.g. from Intel AVX to Intel AVX-512.

Moreover, there are ISAs that are guilty of various blunders, which lower the performance many times. For instance, if an ISA does not have rotation instructions, an application whose performance depends a lot on such operations may run up to 3x slower than on an ISA with rotation instructions

Even greater slow-downs happen on ISAs that lack good means for detecting various errors, e.g. when running on RISC-V a program that must be reliable, so it has to check for integer overflows.