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I'm trying to learn about ISAs. And, after taking a class and watching a whole bunch of RISC vs CISC videos, I still don't know 'why' Apple Silicon is faster a
by simple_quest_9 2y ago
I'm trying to learn about ISAs.
And, after taking a class and watching a whole bunch of RISC vs CISC videos, I still don't know 'why' Apple Silicon is faster at a lower power consumption than Intel's chips.
Can someone tell me?
- lights0123 2y agoA big factor is that Apple buys out all of TSMC's capacity for new process nodes, so they get the smallest transistors that run at lower power and higher speeds.
- dagmx 2y agoPeople say this, but it’s a trite trivialization of the architectural choices made beyond just the ISA. When AMD/intel have moved to the same or comparable nodes, they’re not catching up for perf/watt. Lunar Lake will be on the same N3E as M4, so we’ll have to see how it compares.
- AnthonyMouse 2y ago> When AMD/intel have moved to the same or comparable nodes, they’re not catching up for perf/watt. They are though? If you compare the Apple and AMD processors that are both on e.g. TSMC 5nm, the AMD ones have if anything better performance per watt. Compare the 7945HX3D to any Apple CPU on the same 5nm process with a similar TDP and the 7945HX3D will generally have similar if not better performance. But people keep doing comparisons right after Apple is the first to release a CPU on a new TSMC process, and naturally if you don't compare like with like, the newer process is more efficient. Another reason people keep getting confused is that AMD isn't afraid to go back and release updated models of older cores on their original process nodes. So for example the 7730U is from 2023, it's just a year old, but it's Zen 3 on the 7nm process they've been using since 2019. Meanwhile the "real" 2023 release was Zen 4 on 4nm (e.g. 7840U), but don't pick the wrong one to do your comparison.
- KingOfCoders 2y ago"Compare the 7945HX3D to any Apple CPU on the same 5nm process with a similar TDP and the 7945HX3D will generally have similar if not better performance." Sounds interesting, do you have numbers - s I get this argument often, that on the same node, Apple is so much better.
- AnthonyMouse 2y agoSo here's each vendor's first CPU on TSMC 5nm. This is actually the only process they've both used, and AMD only used it for a couple of models -- they tend to use all the ones Apple doesn't (7nm, 6nm, 4nm vs. 5nm and 3nm), which makes direct comparisons rare. But this is one: https://nanoreview.net/en/cpu-compare/apple-m1-ultra-vs-amd-ryzen-9-7945hx3d https://nanoreview.net/en/cpu-compare/apple-m1-ultra-vs-amd-... They both have a similar TDP, a similar number of cores and the performance on most tests is similar or better for the 7945HX3D.
- KingOfCoders 2y ago<3 OT: I think it also shows the bad iGPU compared to Apples offerings, so too many x86 laptops have additional GPUs, which reduces battery life (we'll see what Strix brings) Also both have 16 performance cores, but the Ryzen is faster in multicore. The Ryzen is one year later b/c due to node access/ costs. Doesn't look like "far behind".
- AnthonyMouse 2y agoThere is nothing inherently inefficient about a discrete GPU. Discrete GPUs often have extremely good performance per watt. That's just not the same thing as having a low TDP. Performance per watt is higher when something is twice as power hungry but three times faster.
- KingOfCoders 2y agoNot an electrical engineer, my GPU board has lots of additional chips and VRMs, and I do think those should take additional power. All of these are cooled which means they convert power into heat, so I would assume a discrete board draws more power than a SoC. But as I've said, not an electrical engineer (Just some electrical engineering exams at university).
- KingOfCoders 2y agoAs others have been pointing out, Lunar Lake is on N3B and N3E (M4) is booked up by Apple.
- wmf 2y agoNotably, Lunar Lake and Apple M4 are made on the same TSMC N3E process and have similar specs so we can perform an apples to apples comparison (sorry not sorry).
- DeathArrow 2y ago>Notably, Lunar Lake and Apple M4 are made on the same TSMC N3E Lunar Lake will be on N3B process.
- KingOfCoders 2y agoThanks for the clarification.
- wmf 2y agoSame as M3 then.
- supertrope 2y agoPower Performance Area. Area is how much wafer area each chip and the features within a chip use. Apple optimizes for the first two and sacrifices the third. Because they mark up their products a lot, are vertically integrated, and they move millions of devices they can sink a lot of $ into bigger chips made on bleeding edge lithography. More area means bigger caches, higher instruction level parallelism. Hiring lots of top chip designers gets better results too.
- brigade 2y agoThey're only large compared to other ARM cores, and Cortex-X4 is pretty close nowadays. AMD and especially Intel have a significantly larger per-core area budget; they have to in order to clock past 5 GHz.
- wmf 2y agoApple is just better at designing CPUs but nobody wants to hear that. CPU design requires sweating thousands of details. There's no one cool trick.
- KingOfCoders 2y agoIn which way are they better? Jim Keller (and others) worked on Apple CPUs and on AMDs Ryzen. So when leaving Apple, he (they) became stupid?
- simple_quest_9 2y agoYes, but, 'where' are they better than Intel and AMD?
- wmf 2y agoEverywhere.
- KingOfCoders 2y agoNo (less) legacy (smaller chip die area, faster and easier decoder). Paying prime prices for TSMCs newest nodes, one node ahead of everyone else. Bigger (more expensive) caches. Faster memory interface. Nothing magic. But the deep integration with better margins and higher end product prices allows Apple to have more expensive CPUs than the competition.
- DeathArrow 2y ago>No (less) legacy (smaller chip die area, faster and easier decoder) What do you consider legacy? Can you point out how much it does affect die area and the instruction decoder? If I'd take a guess it's not more than maybe 2 or 3%.
- KingOfCoders 2y ago3% is 3% - IPC gains for Ryzen would not be 15% but 18%. But I do think the benefits are in a faster and easier decoder, and easier memory interfaces etc. Not a hardware engineer, from a software engineer dropping legacy code makes development of new features easier and more cost efficient, so I can concentrate on other things. But as I've said, I'm no hardware engineer.
- mkl 2y ago3% of die area is not the same as 3% of IPC.
- KingOfCoders 2y agoYou're right. I wasn't clear, I didn't mean IPC goes up by 3% with that change, I've used that as an example of how 3% can be significant.
- deleted 2y ago[deleted]
- DeathArrow 2y agoApple optimizes for IPC and power, that means wide architecture and large die area. The rest optimize for throughput and cost. That means small dies and higher power consumption. AMD and Intel can do what Apple does and Apple can do what AMD and Intel do, but each company chooses the path they believe it makes more sense for them.
- adrian_b 2y agoWhen first launched, the Apple CPUs did about 50% more work per clock cycle (i.e. more instructions executed simultaneously) than the best Intel and AMD CPUs, enabling a 3.2 GHz Apple CPU to have the same single-thread speed as a 4.8 GHz Intel or AMD CPU. Because the power consumption grows at least quadratically with the clock frequency, having the same speed at a lower clock frequency provides better energy efficiency. Meanwhile, the difference in IPC (instructions per clock cycle) between Apple and the others has been reduced, but Apple still has a healthy advantage. The different microarchitecture explains the energy efficiency advantage for single-threaded tasks. On the other hand, for multi-threaded tasks, the power consumption per chip area is limited by cooling and the energy required to do a quantity of useful work (which is done by switching a certain number of logic gates) is mainly determined by the parameters of the CMOS process used to make the CPU die (assuming that the CPU designers are not incompetent). So for multi-threaded tasks the better energy efficiency of the Apple CPUs has been determined mostly by the fact that they have been the only company able to use the latest and greatest TSMC CMOS process.
- KingOfCoders 2y agoApple jumped onto the split-core train early on. High performance cores for being good in IPC and low performance cores for multi core workloads with overall low power usage. Apple has the benefit of controlling the OS, so no scheduler problems. Intel came later but seems to make good advances, if you look at e-Cores in Lunar Lake. I predict AMD will go the same route (way bezond 5c), now that x86 also focuses on performance/watt and not peak performance (if you watch the announcements).
- adrian_b 2y agoApple jumped onto the split-core train early on, because it was the first having access to more advanced manufacturing processes. CPUs with big and little cores were not useful for the old "14 nm" manufacturing processes used by Intel for Skylake and its derivatives, because in those processes the power consumption of a core and its speed could be varied in a very large range, e.g. for the extremes of the supply voltage, the clock frequency of a laptop CPU core could vary between 0.6 GHz and 4.5 GHz, corresponding to a variation of the power consumption per core of even 50 times. Modern processes have more constrained ranges for the optimal operating parameters of the transistors, so it has become better to split the cores into several classes that are designed with different trade-offs between power consumption and performance, instead of attempting to use the same core both at very low and at very high power consumptions. The decision to use 2 or more kinds of cores to cover the entire curve of performance vs. power consumption, when you can no longer cover it by varying the operating parameters of a single kind of core, is a no-brainer. While for the CPUs with a small number of cores, like for smartphones, tablets and light laptops, the existence of multiple kinds of cores is needed for optimum energy efficiency, the CPUs for desktops or big laptops with a great number of medium-size cores, like Raptor Lake, have them for a different reason. The big Intel cores, in the quest for maximum single-thread performance, have poor performance per chip area. The medium-size cores have better performance per area, so in the same limited chip area you can put more cores, increasing the multi-threaded performance beyond what would be obtained by filling the same area with big cores. Nevertheless, AMD has a better strategy than Intel, because their big cores with high single-thread performance and their "compact" cores with better performance per chip area are logically equivalent, avoiding the software incompatibility problems caused by Intel.
- mmaniac 2y agoLots of reasons, but RISC vs CISC has little to do with it. Apple have access to the newest and best fabbing processes from TSMC. That alone can put a chip a generation ahead in terms of efficiency. Intel foundries have been struggling for years and AMD only get TSMC's scraps a few years later. Increasing clock speed is the easiest way to increase performance, but power increases quadratically with clock speed so it's very inefficient. Apple clock their processors pretty low and instead focused on increasing instructions-per-clock, which is generally more efficient but requires more die area. As an example, a lot of noise was made about the M1's 8-wide decoder, twice as wide as contemporary x86 chips, which is an important bottleneck for IPC. Increasing instructions-per-clock requires much bigger CPU cores, and the dies Apple use for their SoCs are famously enormous. While other chip manufacturers are very conscious of performance/$, Apple's vertical integration gives them wider margins and their customers are much less sensitive to value. So Apple can afford to spend a lot more on bigger chips that are on par in performance but have much greater efficiency.
- jorvi 2y ago> Increasing instructions-per-clock requires much bigger CPU cores, and the dies Apple use for their SoCs are famously enormous. While other chip manufacturers are very conscious of performance/$, Apple's vertical integration gives them wider margins and their customers are much less sensitive to value. So Apple can afford to spend a lot more on bigger chips that are on par in performance but have much greater efficiency. This is the money shot. Margins on Android phones are often in the single digit percentages, they have even had periods where they’re negative. Qualcomm or Mediatek could easily make phat chips but there would be almost no market for them. I am very curious what the actual performance of the Snapdragon X is going to be. Laptop margins are often just as thin, so it can’t be too expensive a chip either..
- mmaniac 2y agoApparently[1] Snapdragon X is cost-competitive with Intel. That article discusses Raptor Lake on Intel 7, which is known to have razor thin margins, but Meteor Lake is reportedly expensive too. Intel's uncompetitive foundries continue to be an millstone around their neck. I'm sceptical of Snapdragon X's real world performance until these things actually ship. There's a lot of big promises made. Intel promises big too. [1]https://videocardz.com/newz/snapdragon-x-series-chips-cost-only-half-as-much-as-intel-raptor-lakes-with-battery-life-up-to-98-higher https://videocardz.com/newz/snapdragon-x-series-chips-cost-o...
- ylk1 2y agoRead this: https://www.reddit.com/r/explainlikeimfive/comments/1ch6ifi/comment/l25hsgu/?utm_source=share&utm_medium=web3x&utm_name=web3xcss&utm_term=1&utm_content=share_button https://www.reddit.com/r/explainlikeimfive/comments/1ch6ifi/...