Arm's Cortex-A76 CPU Unveiled: Taking Aim at the Top for 7nm
by Andrei Frumusanu on May 31, 2018 3:01 PM EST- Posted in
- CPUs
- Arm
- Smartphones
- Mobile
- SoCs
- Cortex-A76
Conclusion & Thoughts
The Cortex A76 presents itself a solid generational improvement for Arm. We’ve been waiting on a larger CPU microarchitecture for several years now, and while the A76 isn’t quite a performance monster to compete with Apple’s cores, it shows how important it is to have a balanced microarchitecture. This year all eyes were on Samsung and the M3 core, and unfortunately the performance increase came at a great cost of power and efficiency which ended up making the end-product rather uncompetitive. The A76 drives performance up but on every step of the way it still deeply focused on power efficiency which means we’ll get to see the best of both worlds in end products.
In general Arm promises a 35% performance improvement which is a significant generational uplift. Together with the fact that the A76 is targeted to be employed in 7nm designs is also a boost to the projected product.
I’m having some reservations in terms of the performance targets and if vendors will indeed release the SoC with quad-core clock rates of up to 3GHz – based on what I’ve heard from vendors that seems like a rather very optimistic target. Even then, a reduced clock frequency still brings significant benefits, and it’s especially on the efficiency side where Arm should be lauded for continuing to place great focus on.
Whether my projections are correct or not is something we’ll have to see in actual products, but fact is that we *will* see significant efficiency benefits in the next generation of SoCs which should bring both an notable performance improvement as well as battery life improvement to the user. Arm’s focus here on the user experience seems to be exemplary and I hope vendors will be able to implement the core based on Arm’s guidance and reach the targeted metrics.
The Cortex A76 is said to have already come back in working silicon at two partners and we’ll very likely see it shipping in commercial products by the end of the year. I won’t be beating around the bush here as Huawei and HiSilicon’s product cycle schedule makes it obvious that they’re likely one of the launch partners for the product. Qualcomm has also doubled down on using Arm cores in the mobile space so we should also be seeing the next generation Snapdragon SoCs employ the A76. Among the big players, it’s Samsung LSI which is going to have a tough time – the A76 doesn’t seem to greatly outperform the M3, so at least in theory, the M4’s focus will need to be solely on power efficiency. Then again Arm is very open about their design goals; half the area and half the power at similar performance is something that’s going to be hard to compete against.
The Cortex A76 is said to be the baseline microarchitecture on which Arm will iterate over the next 2 generations at least. Arm has been able to execute their yearly beat roadmap on time for 5 generations now and with yearly 20-25% CAGR it’s going to be a very interesting next couple of years as the mobile space is very quickly approaching the performance of desktop CPUs.
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name99 - Friday, June 1, 2018 - link
FFS. the issue is NOT "Older batteries might not be able to supply enough power for a big core", it is that the battery cannot supply enough CURRENT.If you can't be bothered to understand the underlying engineering issue and why the difference between current and power matters, then your opinions on this issue are worthless.
serendip - Friday, June 1, 2018 - link
Whoa, chill there buddy, I'm not an electrical engineer.name99 - Friday, June 1, 2018 - link
"Does anyone actually use the full performance of the A11 or A12 in daily tasks? "Absolutely. I've updated iPhones every two years, and every update brings a substantial boost in "fluidity" and just general not having to wait. I can definitely feel the difference between my iPhone 7 and my friend's iPhone X; and I expect I will likewise feel the difference when I get my iPhone 2018 edition (whatever they are naming them this year...)
Now if you want to be a tool, you can argue "that's because Apple's software sux. Bloat, useless animations, last good version of iOS was version 4, blah blah". Whatever.
MOST people find more functionality distributed throughout the dozens of little changes of each new version of the OS, and MOST people find the "texture" of the OS (colors, animations, etc) more pleasant than having some sort of text only Apple II UI, though doubtless that could run at a 10,000 fps.
So point is, yeah, you DO notice the difference on phones. Likewise on iPads. I use my iPad to read technical PDFs, and again, each two year update provides a REALLY obvious jump in how quickly complicated PDF pages render. With my very first iPad 1 there was a noticeable wait almost every page (only hidden, usually, because of page caching). By the A10X iPad Pro it's rare to encounter a PDF page that ever makes you wait, cached or not.
I've also talked about in the past about Wolfram Player, a subset of Mathematica for iPad. This allows you to interact with Mathematica "animations" (actually they're 3D interactive objects you construct that change what is displayed depending on how you move sliders or otherwise tweak parameters). These are calculating what's to be displayed (which might be something like numerically solving a partial differential equation, then displaying the result as a 3D object) in realtime as you move a slider.
Now this is (for now) pretty specialized stuff. But Wolfram's goal, as they fix the various bugs in the app and implement the bits of Mathematica that don't yet work well (or at all), is for these things to be the equivalent of video today. We used to put up with explanations (in books, or newspapers) that were just words. Then we got BW diagrams. Then we got color diagrams. Then we got video. Now we have web sites like NYT and Vox putting up dynamic explainers where you can move sliders --- BUT they are limited to the (slow) performance of browsers, and are a pain to construct (both the UI, and the underlying mathematical simulation). Something like Mathematica's animations are vastly more powerful, and vastly easier to create. One day these will be as ubiquitous as video is today, just one more datatype that gets passed around. But for them to work well requires a CPU that can numerically solve PDEs in real time on your mobile device...
techconc - Tuesday, June 5, 2018 - link
The benefits of having a fast single core are seen on most common operations, including UI and scrolling, etc. Moreover, Apple has demonstrated that a powerful core can in fact be more efficient in race to sleep conditions whereby it completes the work more quickly then sleeps. The overall effect is a more responsive system that is just as efficient overall.tipoo - Tuesday, September 4, 2018 - link
Sure, every time I render a webpage.ZolaIII - Friday, June 1, 2018 - link
Well let's put it this way the A73 which is two instructions wide had a no problems on 14 nm FinFET, A76 is 4 instruction wide & for a sakes of argument let's say 2x the size. So switching from 14 nm to 7nm (60% reduction on power) cower it, A76 is approximately 65% faster than A73 MHz per MHz so its able to deliver approximately the 1.8x performance per same DTP. Second part is a manufacturing process in comparison to the core size. The FinFET structure transistors leak as hell when the 2.1~2.2 GHz limit is reached disregarding of OEM, vendor/foundry. So if you employ 50% wider core's (6 instructions wide) that won't cross the 2.1~2.2 GHz limit it's not the same as if you push the limit of the 4 instructions wide one to 3GHz as the power consumption will be doubled compared to the same one operating on 2.1~2.2 GHz & in the end you lose both on theoretical true output (performance) and power consumption metric but it still costs you 33% less. In reality it's much harder to feed optimally the wider core (especially on something which is mobile OS). ARM (cowboy camp) did a great work optimising instruction latency and cache latency/true output which will both increase real instruction output per clock & help predictor without significant increase in needed resources (cost - size) & A76 is a first of it's kind (CPU ever) regarding implanted solution for this. However thing that ARM didn't deliver is a better primary work horse which could make a difference in base user experience. A55 aren't exactly the power haus regarding performance & now their is more headroom regarding power when scaled down to the 7 nm, enough for let's say A73 on slightly lower clocks to replace the A55 (A73 is 1.6x integer performance of A55 MHz/MHz so A73 @ 1.7GHz = A55 @ 2.7 GHz while switching from 14 to 7nm would make DTP of A55 to A73 the same). But A73 doesn't work on DinamIQ cluster. So there is a need for the new two instructions wide OoO core with merged architectural advancements (front end, predictor, cache, ASIMD...) as in order ones did hit the brick wall long time ago.vladx - Friday, June 1, 2018 - link
> So switching from 14 nm to 7nm (60% reduction on power)That might've been true if both 14nm and 7nm fab processes were actually the real deal. But alas, they are not.
ZolaIII - Saturday, June 2, 2018 - link
Based on the TSMC projections 60% power reduction.beginner99 - Monday, June 4, 2018 - link
The things is that CPU power use might already be a small part of phone power use. The display usually being the main consumer and when the display isn't running, most likely the big core will also not be running. Saving 40% power sounds great on paper. But in real designs it will already be smaller and the total impact on phone battery life will be much, much smaller. Single-digit percentage probably depending on how much you use. The more it is idle, the less the big core efficiency matters.Dazedconfused - Thursday, May 31, 2018 - link
I get this, but when comparing an iPhone x and say an Android flagship next to each other in pretty much every day to day task, they appear evenly matched. There are some good comparisons on YouTube. There are definitely strengths to each platform, but it's not clear cut at all