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Are ARM processors inherently power efficient? I doubt. Performance per watt is increasing due to the lithography. Also, Devon’s paradox.
by ahoka 1y ago
Are ARM processors inherently power efficient? I doubt.
Performance per watt is increasing due to the lithography.
Also, Devon’s paradox.
- ggm 1y agoAside from lithography there's clever design. I don't think you can quantify that but it's not nothing.
- eb0la 1y agoActually power efficiency was a side effect of having a straightforward design in the first ARM processor. The BBC needed a cheap (but powerful) processor for the Acort computer and a RISC chip was When ARM started testing their processor, they found out it draw very little power... ... the rest is history.
- delaminator 1y agoThe BBC Micro had a 6502
- iainmerrick 1y agoYou're getting your history mixed up. Acorn won the bid to make the original BBC home computer, with a 6502-based design. Acorn later designed their own 32-bit chip, the ARM, to try to leapfrog their competitors who were moving to the 68000 or 386, and later spun off ARM as a separate company.
- jorvi 1y agoThey aren't inherently power efficient because of technical reasons, but because of design culture reasons. Traditionally x86 has been built powerful and power hungry and then designers scaled the chips down whereas it's the opposite for ARM. For whatever reason, this also makes it possible to get much bigger YoY performance gains in ARM. The Apple M4 is a mature design[0] and yet a year later the M5 is CPU +15% GPU +30% memory bandwidth +28%. The Snapdragon Elite X series is showing a similar trajectory. So Jim Keller ended up being wrong that ISA doesn't matter. Its just that it's the people in the ISA that matter, not the silicon. [0] its design traces all the way back to the A12 from 2018, and in some fundamental ways even to the A10 from 2016.
- IshKebab 1y agoDo you have any actual evidence for that? Intel does care about power efficiency - they've been making mobile CPUs for decades. And I don't think they are lacking intelligent chip designers. I would need some strong evidence to make me think it isn't the ISA that makes the difference.
- high_na_euv 1y agoIsn't Lunar Lake first mobile chip with focus on energy eff? And it is reasonably efficient We will see how big improvement is it's successor panther lake in January on 18A node >I would need some strong evidence to make me think it isn't the ISA that makes the difference. It is like saying that Java syntax is faster than C# syntax. Everything is about the implementation: compiler, jit, runtime, stdlib, etc If you spent decades of effort on peformance and ghz then don't be shocked that someone who spent decades on energy eff is better in that category
- cogman10 1y ago> Isn't Lunar Lake first mobile chip with focus on energy eff? Not by a long shot. Over a decade ago, one of my college professors was an ex-intel engineer who worked on Intel's mobile chips. He was even involved in an Intel ARM chip that ultimately never launched (At least I think it never launched. It's been over a decade :D). The old conroe processors were based on Intel's mobile chips (Yonah). Netburst didn't focus on power efficiency explicitly so and that drove Intel into a corner. Power efficiency is core to CPU design and always has been. It's easy create a chip that consumes 300W idle. The question is really how far that efficiency is driven. And that may be your point. Lunar Lake certainly looks like Intel deciding to really put a lot of resource on improving power efficiency. But it's not the first time they did that. The Intel Atom is another decades long series which was specifically created with power in mind (the N150 is the current iteration of it).
- mrsmrtss 1y agoActually, if you had made an opposite example, it might have gone against your point. ;) C# gives you a lot more control over memory and other low-level aspects, after all.
- iberator 1y agoYes they are. RISC philosophy apart from instruction set is also low gate count (so less energy used). Nvidia can design super clean solution fron scratch - i can bet 50$ that its gonna be more efficient in MIPS/watt
- bluGill 1y agoMost of the gates on a cpu are not instruction decoding.
- cwizou 1y agoAccording to an AMD engineer I asked at the time, when they evaluated Ryzen/K12, it was "maybe" a 15% advantage for ARM depending on scenarios. The efficiency came solely from the frontend which is a lot heavier on x86, and stay up longer because decoding is way more complex. The execution units were the same (at least mostly, I think, might be misremembering) so once you are past the frontend there's barely any difference in power efficiency.
- ksec 1y ago>Are ARM processors inherently power efficient? I doubt. In theory yes. In practice none of the x86 design are even close, the lunar lake at same wattage barely competes with M1. And M1 is one node generation behind.