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AMD claims Arm ISA doesn't offer efficiency advantage over x86

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Re: AMD claims Arm ISA doesn't offer efficiency advantage over x86

#311

Post by pezezin »

camel-cdr wrote: post #305
pezezin wrote: post #292

Earlier quoted context omitted.

But those initiatives are focused on servers. What about desktops and laptops? Cellphones? SBC like the Raspberry Pi? That is my concern.

This is also supposed to be for desktops/laptops afaik, idk about phones. Edit, this part of the server platforms spec certainly: https://github.com/riscv-non-isa/riscv-brs/blob/main/intro.a... > BRS-I is expected to be used by general-purpose compute devices such as servers, desktops, laptops and other devices with industry expectations on silicon vendor, OS and software ecosystem interoperability.

Thank you, I had missed that part.

It would be great indeed if there is a standardized boot process that every OS can use, I think it would greatly help with RISC-V adoption.

Re: AMD claims Arm ISA doesn't offer efficiency advantage over x86

#313

Post by bpavuk »

mojuba wrote: post #295
exmadscientist wrote: post #247

Earlier quoted context omitted.

Yes, Intel/AMD cannot match Apple in efficiency. But Apple cannot beat Intel/AMD in single-thread performance. (Apple marketing works very hard to convince people otherwise, but don't fall for it.) Apple gets very, very close, but they just don't get there. (As well, you might say they get close enough for practical matters; that might be true, but it's not the question here.) That gap, however small it might be for…

> Apple has a max-efficiency design that's excellent for personal computing. Intel/AMD have aging max-performance designs that do beat Apple at absolute peak... Can you explain then, how come switching from Intel MBP to Apple Silicon MBP feels like literally everything is 3x faster, the laptop barely heats up at peak load, and you never hear the fans? Going back to my Intel MBP is like going back to stone age computi…

it all comes down to thermal budget of something as thin as MBP.

Re: AMD claims Arm ISA doesn't offer efficiency advantage over x86

#314

Post by fxtentacle »

mojuba wrote: post #295
exmadscientist wrote: post #247

Earlier quoted context omitted.

Yes, Intel/AMD cannot match Apple in efficiency. But Apple cannot beat Intel/AMD in single-thread performance. (Apple marketing works very hard to convince people otherwise, but don't fall for it.) Apple gets very, very close, but they just don't get there. (As well, you might say they get close enough for practical matters; that might be true, but it's not the question here.) That gap, however small it might be for…

> Apple has a max-efficiency design that's excellent for personal computing. Intel/AMD have aging max-performance designs that do beat Apple at absolute peak... Can you explain then, how come switching from Intel MBP to Apple Silicon MBP feels like literally everything is 3x faster, the laptop barely heats up at peak load, and you never hear the fans? Going back to my Intel MBP is like going back to stone age computi…

If you take a peak-performance-optimized design (the Intel CPU) and throttle it down to low power levels, it will be slower than a design optimized for low power (the Apple CPU).

"let's compare oranges to oranges"

That's impossible because Apple has bought up most of TSMC's 3nm production capacity. You could try to approximate by comparing Apple M4 Max against NVIDIA B300 but that'll be a very one-sided win for NVIDIA.

Re: AMD claims Arm ISA doesn't offer efficiency advantage over x86

#315

Post by matja »

jcranmer wrote: post #146
codedokode wrote: post #124

Earlier quoted context omitted.

x86 decoding must be a pain - I vaguely remember that they have trace caches (a cache of decoded micro-operations) to skip decoding in some cases. You probably don't make such caches when decoding is easy. Also, more complicated decoding and extra caches means longer pipeline, which means more price to pay when a branch is mispredicted (binary search is a festival of branch misprediction for example, and I got 3x acc…

> x86 decoding must be a pain So one of the projects I've been working on and off again is the World's Worst x86 Decoder, which takes a principled approach to x86 decoding by throwing out most of the manual and instead reverse-engineering semantics based on running the instructions themselves to figure out what they do. It's still far from finished, but I've gotten it to the point that I can spit out decoder rules. A…

Missing a 0 at the end

Re: AMD claims Arm ISA doesn't offer efficiency advantage over x86

#316

Post by ohdeargodno »

jorvi wrote: post #224
torginus wrote: post #18

Earlier quoted context omitted.

I remember reading this Jim Keller interview: https://web.archive.org/web/20210622080634/https://www.anand... Basically the gist of it is that the difference between ARM/x86 mostly boils down to instruction decode, and: - Most instructions end up being simple load/store/conditional branch etc. on both architectures, where there's literally no difference in encoding efficiency - Variable length instruction has pretty…

Nice followup to your link: https://chipsandcheese.com/p/arm-or-x86-isa-doesnt-matter . Personally I do not entirely buy it. Intel and AMD have had plenty of years to catch up to Apple's M-architecture and they still aren't able to touch it in efficiency. The PC Snapdragon chips AFAIK also offer better performance-per-watt than AMD or Intel, with laptops offering them often having 10-30% longer battery life at simila…

[dead]

Re: AMD claims Arm ISA doesn't offer efficiency advantage over x86

#318

Post by ohdeargodno »

boxed wrote: post #309
ben-schaaf wrote: post #263

Earlier quoted context omitted.

> Personally I do not entirely buy it. Intel and AMD have had plenty of years to catch up to Apple's M-architecture and they still aren't able to touch it in efficiency. The PC Snapdragon chips AFAIK also offer better performance-per-watt than AMD or Intel, with laptops offering them often having 10-30% longer battery life at similar performance. Do not conflate battery life with core efficiency. If you want to measu…

He said "per watt", that's still true. You just talked about max throughput, which no one is discussing.

It's not, because Apple purposefully lied on their marketing material. Letting a 3090 go on full blast brings it pretty much in line in perf/watt. Your 3090 will not massively thermal throttle after 30 minutes either, but the M1 Ultra will.

So, yes, if you want to look good on pointless benchmarks, a M1 ultra ran for 1 minute is more efficient than a downclocked 3090.

Re: AMD claims Arm ISA doesn't offer efficiency advantage over x86

#319

Post by whatevaa »

diddid wrote: post #240
jorvi wrote: post #224

Earlier quoted context omitted.

Nice followup to your link: https://chipsandcheese.com/p/arm-or-x86-isa-doesnt-matter . Personally I do not entirely buy it. Intel and AMD have had plenty of years to catch up to Apple's M-architecture and they still aren't able to touch it in efficiency. The PC Snapdragon chips AFAIK also offer better performance-per-watt than AMD or Intel, with laptops offering them often having 10-30% longer battery life at simila…

I mean the M1 is nice but pretending that it can do in 110w what the 3090 does with 320w is Apple marketing nonsense. Like if your use case is playing games like cp2077, the 3090 will do 100fps in ultra ray tracing and an M4 Max will only do 30fps. Not to mention it’s trivial to undervolt nvidia cards and get 100% performance at 80% power. So 1/3 the power for 1/3 the performance? How is that smoking anything?

Apple fans drinking apple juice, nothing new with fans, sadly.

Re: AMD claims Arm ISA doesn't offer efficiency advantage over x86

#320

Post by samus »

aredox wrote: post #306
jorvi wrote: post #224

Earlier quoted context omitted.

Nice followup to your link: https://chipsandcheese.com/p/arm-or-x86-isa-doesnt-matter . Personally I do not entirely buy it. Intel and AMD have had plenty of years to catch up to Apple's M-architecture and they still aren't able to touch it in efficiency. The PC Snapdragon chips AFAIK also offer better performance-per-watt than AMD or Intel, with laptops offering them often having 10-30% longer battery life at simila…

>Intel and AMD have had plenty of years to catch up to Apple's M-architecture and they still aren't able to touch it in efficiency. Why would they spend billions to "catch up" to an ecological niche that is already occupied, when the best they could do - if the argument here is right that x86 and ARM are equivalent - is getting the same result? They would only invest this much money and time if they had some expectat…

The problem is that they are slowly losing the mobile markets, while their usual markets are not growing as they used to. AMD is less vulnerable to the issues that arise from that because they are fabless, and they could pivot entirely to GPU or non-x86 markets if they really wanted to. But Intel has fabs (very expensive in terms of R&D and capex) dedicated to products for desktop and server markets that must continue to generate revenue.
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