A8’s CPU: What Comes After Cyclone?

Despite the importance of the CPU in Apple’s SoC designs, it continues to be surprising just how relatively little we know about their architectures even years after the fact. Even though the CPU was so important that Apple saw the need to create their own custom design, and then did two architectures in just the span of two years, they are not fond of talking about just what it is they have done with their architectures. This, unfortunately, is especially the case at the beginning of an SoC’s lifecycle, and for A8 it isn’t going to be any different.

Overall, from what we can tell the CPU in the A8 is not a significant departure from the CPU in A7, but that is not a bad thing. With Cyclone Apple hit on a very solid design: use a wide, high-IPC design with great latency in order to reach high performance levels at low clock speeds. By keeping the CPU wide and the clock speed low, Apple was able to hit their performance goals without having to push the envelope on power consumption, as lower clock speeds help keep CPU power use in check. It’s all very Intel Core-like, all things considered. Furthermore given the fact that Cyclone was a forward-looking design with ARMv8 AArch64 capabilities and already strong performance, Apple does not face the same pressure to overhaul their CPU architecture like other current ARMv7 CPU designers do.

Close Up: "Enhanced Cyclone"

As a result, from the information we have been able to dig up and the tests we have performed, the A8 CPU is not radically different from Cyclone. To be sure there are some differences that make it clear that this is not just a Cyclone running at slightly higher clock speeds, but we have not seen the same kind of immense overhaul that defined Swift and Cyclone.

Unfortunately Apple has tightened up on information leaks and unintentional publications more than ever with A8, so the amount of information coming out of Apple about this new core is very limited. In fact this time around we don’t even know the name of the CPU. For the time being we are calling it "Enhanced Cyclone" – it’s descriptive of the architecture – but we’re fairly certain that it does have a formal name within Apple to set it apart from Cyclone, a name we hope to discover sooner than later.

In any case one of the things we do know about Enhanced Cyclone is that unlike Apple’s GPU of choice for A8, Apple has seen a significant reduction in the die size of the CPU coming from the 28nm A7 to the 20nm A8. Chipworks’ estimates put the die size of Cyclone at 17.1mm2 versus 12.2mm2 for Enhanced Cyclone. On a relative basis this means that Enhanced Cyclone is 71% the size of Cyclone, which even after accounting for less-than-perfect area scaling still means that Enhanced Cyclone is a relatively bigger CPU composed of more transistors than Cyclone was. It is not dramatically bigger, but it’s bigger to such a degree that it’s clear that Apple has made further improvements over Cyclone.

The question of the moment is what Apple has put their additional transistors and die space to work on. Some of that is no doubt the memory interface, which as we’ve seen earlier L3 cache access times are nearly 20ns faster in our benchmarks. But if we dig deeper things start becoming very interesting.

Apple Custom CPU Core Comparison
  Apple A7 Apple A8
CPU Codename Cyclone "Enhanced Cyclone"
ARM ISA ARMv8-A (32/64-bit) ARMv8-A (32/64-bit)
Issue Width 6 micro-ops 6 micro-ops
Reorder Buffer Size 192 micro-ops 192 micro-ops?
Branch Mispredict Penalty 16 cycles (14 - 19) 16 (14 - 19)?
Integer ALUs 4 4
Load/Store Units 2 2
Addition (FP) Latency 5 cycles 4 cycles
Multiplication (INT) Latency 4 cycles 3 cycles
Branch Units 2 2
Indirect Branch Units 1 1
L1 Cache 64KB I$ + 64KB D$ 64KB I$ + 64KB D$
L2 Cache 1MB 1MB
L3 Cache 4MB 4MB

First and foremost, in much of our testing Enhanced Cyclone performs very similarly to Cyclone. Accounting for the fact that A8 is clocked at 1.4GHz versus 1.3GHz for A7, in many low-level benchmarks the two perform as if they are the same processor. Based on this data it looks like the fundamentals of Cyclone have not been changed for Enhanced Cyclone. Enhanced Cyclone is still a very wide six micro-op architecture, and branch misprediction penalties are similar so that it’s likely we’re looking at the same pipeline length.

However from our low-level tests two specific features stand out: integer multiplication and floating point addition. When it comes to integer multiplication Cyclone had a single multiplication unit and it took four cycles to execute. However against Enhanced Cyclone those operations are now measuring in at three cycles to execute. But more surprising is the total Integer multiplication throughput rate; integer multiplication performance has now more than doubled. While this doesn’t give us enough data to completely draw out Enhanced Cyclone’s integer pathways, all of the data points to Enhanced Cyclone doubling up on its integer multiplication units, meaning Apple’s latest architecture now has two such units.

Meanwhile floating point addition shows similar benefits, though not as great as integer multiplication. Throughput is such that there appears to still be three FP ALUs, but like integer multiplication the instruction latency has been reduced. Apple has managed to shave off a cycle on FP addition, so it now completes in four cycles instead of five. Both of these improvements indicate that Enhanced Cyclone is not identical to Cyclone – the additional INT MUL unit in particular – making them very similar but still subtly different CPU architectures.

Apple iPhone Performance Estimates: Over The Years

Outside of these low-level operations, most other aspects of Enhanced Cyclone seem unchanged. L1 cache remains at 64KB I$ + 64KB D$ per CPU core, where it was most recently doubled for Cyclone. For L2 cache Chipworks believes that there may be separate L2 caches for each CPU core, and while L2 cache bandwidth is looking a little better on Enhanced Cyclone than on Cyclone, it’s not a “smoking gun” that would prove the presence of separate L2 caches. And of course, the L3 cache stands at 4MB, with the aforementioned improvements in latency that we’ve seen.

To borrow an Intel analogy once more, the layout and performance of Enhanced Cyclone relative to Cyclone is quite similar to Intel’s more recent ticks, where smaller feature improvements take place alongside a die shrink. In this case Apple has their die shrink to 20nm; meanwhile they have made some small tweaks to the architecture to improve performance across several scenarios. At the same time Apple has made a moderate bump in clock speed from 1.3GHz to 1.4GHz, but it’s nothing extreme. Ultimately while two CPU architectures does not constitute a pattern, if Apple were to implement tick-tock then this is roughly what it would look like.

Moving on, after completing our low-level tests we also wanted to spend some time comparing Enhanced Cyclone with its predecessor on some high level tests. The low-level tests can tell us if individual operations have been improved while high level tests can tell us something about what the performance impact will be in realistic workloads.

For our first high level benchmark we turn to SPECint2000. Developed by the Standard Performance Evaluation Corporation, SPECint2000 is the integer component of their larger SPEC CPU2000 benchmark. Designed around the turn of the century, officially SPEC CPU2000 has been retired for PC processors, but with mobile processors roughly a decade behind their PC counterparts in performance, SPEC CPU2000 is currently a very good fit for the capabilities of Cyclone and Enhanced Cyclone.

SPECint2000 is composed of 12 benchmarks which are then used to compute a final peak score. Though in our case we’re more interested in the individual results.

SPECint2000 - Estimated Scores
  A8 A7 % Advantage

Keeping in mind that A8 is clocked 100MHz (~7.7%) higher than A7, all of the SPECint2000 benchmarks show performance gains above and beyond the clock speed increase, indicating that every benchmark has benefited in some way. Of these benchmarks MCF, GCC, PerlBmk and GAP in particular show the greatest gains, at anywhere between 20% and 55%. Roughly speaking anything that is potentially branch-heavy sees some of the smallest gains while anything that plays into the multiplication changes benefits more.

MCF, a combinatorial optimization benchmark, ends up being the outlier here by far. Given that these are all integer benchmarks, it may very well be that MCF benefits from the integer multiplication improvements the most, as its performance comes very close to tracking the 2X increase in multiplication throughput. This also bodes well for any other kind of work that is similarly bounded by integer multiplication performance, though such workloads are not particularly common in the real world of smartphone use.

Our other set of comparison benchmarks comes from Geekbench 3. Unlike SPECint2000, Geekbench 3 is a mix of integer and floating point workloads, so it will give us a second set of eyes on the integer results along with a take on floating point improvements.

Geekbench 3 - Integer Performance
  A8 A7 % Advantage
992.2 MB/s
846.8 MB/s
1.93 GB/s
1.64 GB/s
Twofish ST
58.8 MB/s
55.6 MB/s
Twofish MT
116.8 MB/s
110.0 MB/s
495.1 MB/s
474.8 MB/s
975.8 MB/s
937 MB/s
109.9 MB/s
102.2 MB/s
219.4 MB/
204.4 MB/s
BZip2Comp ST
5.24 MB/s
4.53 MB/s
BZip2Comp MT
10.3 MB/s
8.82 MB/s
Bzip2Decomp ST
8.4 MB/
7.6 MB/s
Bzip2Decomp MT
16.5 MB/s
15 MB/s
19 MP/s
16.8 MPs
37.6 MP/s
33.3 MP/s
JPG Decomp ST
45.9 MP/s
39 MP/s
JPG Decomp MT
89.3 MP/s
77.1 MP/s
1.26 MP/s
1.14 MP/s
2.51 MP/s
2.26 MP/s
PNG Decomp ST
17.4 MP/s
15.1 MP/s
PNG Decomp MT
34.3 MPs
29.6 MP/s
Sobel ST
71.7 MP/s
58.1 MP/s
Sobel MT
137.1 MP/s
112.4 MP/s
Lua ST
1.64 MB/s
1.34 MB/s
Lua MT
3.22 MB/s
2.64 MB/s
Dijkstra ST
5.57 Mpairs/s
4.04 Mpairs/s
Dijkstra MT
9.43 Mpairs/s
7.26 Mpairs/s

Geekbench’s integer results are overall a bit more muted than SPECint2000’s, but there are still some definite high points and low points among these benchmarks. Crypto performance is among the lesser gains, while Sobel and Dijkstra are among the largest at 21% and 37% respectively. Interestingly in the case of Dijkstra, this does make up for the earlier performance loss Cyclone saw on this benchmark in the move to 64-bit.

Geekbench 3 - Floating Point Performance
  A8 A7 % Advantage
BlackScholes ST
7.85 Mnodes/s
5.89 Mnodes/s
BlackScholes MT
15.5 Mnodes/s
11.8 Mnodes/s
Mandelbrot ST
929.4 MFLOPS
Mandelbrot MT
Sharpen Filter ST
981.7 MFLOPS
Sharpen Filter MT
Blur Filter ST
Blur Filter MT
N-Body ST
735.8 Kpairs/s
587.8 Kpairs/s
N-Body MT
1.46 Mpairs/s
1.17 Mpairs/s
Ray Trace ST
2.76 MP/s
2.23 MP/s
Ray Trace MT
5.45 MP/s
4.49 MP/s

While the low-level floating point tests we ran earlier didn’t show as significant a change in the floating point performance of the architecture as it did the integer, our high level benchmarks show that floating point tests are actually faring rather well. Which goes to show that not everything can be captured in low level testing, especially less tangible aspects such as instruction windows. More importantly though this shows that Enhanced Cyclone’s performance gains aren’t just limited to integer workloads but cover floating point as well.

Overall, even without a radical change in architecture, thanks to a combination of clock speed increases, architectural optimizations, and memory latency improvements, Enhanced Cyclone as present in the A8 SoC is looking like a solid step up in performance from Cyclone and the A7. Over the next year Apple is going to face the first real competition in the ARMv8 64-bit space from Cortex-A57 and other high performance designs, and while it’s far too early to guess how those will compare, at the very least we can say that Apple will be going in with a strong hand. More excitingly, most of these performance improvements build upon Apple’s already strong single-threaded IPC, which means that in those stubborn workloads that don’t benefit from multi-core scaling Apple is looking very good.

A8: Apple’s First 20nm SoC A8’s GPU: Imagination Technologies’ PowerVR GX6450
Comments Locked


View All Comments

  • Caliko - Tuesday, October 6, 2015 - link

    A good phone runs its own OS.

    You and that moron don't understand HD so your obsession is invalid.
  • echtogammut - Tuesday, September 30, 2014 - link

    He isn't wrong about anything he said, but I just can't imagine getting worked up enough to say it. As a current Apple user/developer, I have every Apple product. I like their stuff, but I can't say I am obsessed about it. I also have a lot of the competing products, so I am constantly toying with all of them. When my current iPhone breaks, I will probably replace it with a Sony Xperia Z3 compact, because it looks like a perfect phone for me. I am not interested in a bigger phone and I would like something that is waterproof, because I run or ride a rain, sleet or shine. I personally think Apple is falling behind in the world of business and multi-use devices. I am seeing a lot of customers whom I developed business apps for iOS coming back and wanting to move to Microsoft or Android platforms because the devices are more powerful and offer more robust features.
  • GerryS - Wednesday, October 1, 2014 - link

    I agree. He makes some good points, though most of them are seriously overstated. For most users (yes, nearly everyone in my experience) a "pretty dang good" display is about as good as we can be bothered to look for. I actually like the display on my iPhone 4s. I've never had a complaint, except that it is small, so I got an iPad.

    See, I don't actually like it that Apple went for big phones. I carry my phone in my pants pocket. The 6 might be about the limit of the size phone I want. If I could get an updated 4s with the processor and other basic features of the 6, that's what I'd buy.

    So, for most consumers, we want something that works. I had 4 Android phones before Verizon got the iPhone. I liked them pretty well, but they kept breaking. I went to Apple for dependability, and have not been disappointed. I've only had a couple of problems (even with my jailbreaks), and they've always been easy to fix.

    I do like it when Apple leads the way, but it would be silly to expect them to have all of the advances. So many people compare the iPhones to Android phones, listing all of the things that came out first or "better" on Android phones. They seem to forget that there are dozens of companies making Android phones. The best of them have only one or tow innovations at a time - about the same as Apple manages. Apple continues to be one of the leaders, as long as you compare them to one company at a time.

    If you want the universe of advances coming from Android manufacturers, then go buy an Android. We really won't hold it against you. For me, I like my iPhone and iPad. My wife has Android (at my recommendation) because we could get some features that were important to her.
  • Actius - Wednesday, October 1, 2014 - link

    Lol, he is wrong about his engine analogy! Seriously, none of that makes any sense. Haha, and what's a "V8 compressor"? My goodness...people shouldn't talk about things they really don't know. Just reading that was cringe worthy.
  • sigmatau - Thursday, October 2, 2014 - link

    I'm going to guess you are not so dense as to be picking at the spelling but instead don't know what is a v8 Kompressor. Not only one of the best engines that Mercedes made, but also award winning by 3rd parties.
  • techconc - Thursday, October 2, 2014 - link

    Actually, he is either wrong or extremely misguided in almost everything he's said. Feel free to pick your argument of choice. He starts off by saying how the iPhone 6 launch was disastrous. As compared to what? What other vendor will sell 10 million devices on a launch weekend? Even for Apple, it broke their own previous records. I'm genuinely grateful for people that prove they're an idiot right up front. It lets me know I can either skip the rest of the post or read on for purely amusement purposes.
    That's just the conceptual part of the post. His technical observations were equally misguided. Especially with regard to screen quality, etc. Clearly he didn't bother reading the Anandtech review he's commenting on.
  • shm224 - Thursday, October 2, 2014 - link

    @techconc: Sure, what other products you know starts to bend, or totally crap out after the first buggy update, or even have features withdrawn due to more bugs all within the first week of release?
  • akdj - Friday, October 3, 2014 - link

    Really? You're still convinced the iPhone (6 OR 6+) actually and easily 'bends' in the first week? Buggy update? The one available for about two hours that few downloaded and within ten hours of pulling it a fixed update was released? Features withdrawn? I'm intrigued ..as an owner and realist like techconc, the person you responded to... I've GOT to know!
    I'm patiently awaiting my pair of 6+s for my wife and I. We just returned from the mall and the Apple Store specifically playing for almost two hours with them. I built a two minute movie and. Rendered in 1080p in about 35/40 seconds, air dropped to myself. Un. Believable phone. It's. Amazing
    We ordered launch day through our business representative. Lol. Silly me. Ship date estimate is pretty specific, actually a bit ambiguous with the latest update. 11/2-11/28/14:-)
    Oh well. Plenty of time to allow developers to continue updating their apps.
    Between my Air, rMBP 15" and the iPhone 5s /6+, my business of 27 years has been revolutionized. Literally, over the past half decade, as a pilot and sound/video producer...weight savings alone are enough to double our profits. And ½ our setup snd break down times. Even my 'flight bag' of nearly fifty pounds isn't necessary. With three retina minis in the cockpit for redundancy, the 'paper' is still there, but unnecessary any more for updates to plates and Jep charts, winds aloft and weather/traffic ...even diversion airports, filing my flight plan and telling me how thirsty she is! Fuel calculated, with a GPS dongle a tenth the price and 100 fold quicker to lock n track than avionics just a half decade ago provide incredible accuracy. ADSB and TCAS (3D terrain, weather and other traffic/with their specific info; altitude, speed, heading, and Xspnder --- TCAS, a warning system that 'tells you what to do' in conjunction with other planes fitted with the system including all commercial traffic and many GA pilots with ILS certifications ...Alaska can get nasty quick and having to 'duck down' these two systems alone are incredible and 'reasonably priced' advancements!).
    I'm not sure there's a place in my life iOS has t changed. As a father, business owner and operator, little league and wrestling coach, and pilot...each iteration has improved signficantly enough in 'most situations' to justify yearly updates for me. iPhones hold their value. Until the 4s, AT&T was generous and 'allowed' a 12 month subsidized update. With the business I also provide 17 full time employee iPhones so we've been lucky enough to 'recoup' some of the money spent each update
    I just sold an employee's iPhone 5, 32GB AT&T with a cracked screen, scratched to hell and working perfectly. With excellent battery health and perfect camera lens (only scratch-less area of the phone!) for $235 to a local repair guy. He saw me in the mall with the Gazelle box (more than a hundred bucks less) on my way to the USPS. Asked what I was sending. Told him. Showed him a 'picture' or seven before I unboxed it, but he was adamant ...he was able to shine it up with his pieces n parts for $45 or less! Told me it would cost a customer about $210 to do the work but parts were 20% the cost ...labor and time is the price. From there he was confident he could sell it for $325-350 at his kiosk within 24 hours.
    My son has had his fifth generation iPod touch for two years. He's nine. No scratches. No scuffs. Clean a booger or twelve off once a week but other than that, it's completely 'perfect'. These iPhones are built damn near the same. Sleek, thin and well balanced ...no bugs, incredibly quick and unless you're a dumbass and put your $800 pocket computer in your rear pocket of your jeans and SIT on it, you're an idiot ...and you've got to be SIGNIFICANTLY overweight AND hit the precise angle in order to 'mash' 100 pounds of pressure to a 'single point'/torque.
    Can you bend em? Yep. It's been proven and EVERY piece of proof we've seen visually demonstrates the incredible amount of force necessary and in such a way not indicative of daily use or situations a consumer would find themselves in 99.9% of the time.
    Don't. Be. Silly. I respond not only to you but to all those talking like you. Until you've used one. Felt one. Actually spent time with it, it's difficult to understand.
    These are absolute and unequivably the BEST two phones on the maket at this time. With the best and most abundant apps/software optimized to its specs. Support to back it up. And resale value when Ya get bored and ready for a new one. You'll recover your 'down payment' plus fifty percent in many cases ...if you take care of it. Seemingly, they're even more valuable than a same year flagship Samsung Note 2, as I wasn't able to get more than $125 for that joke. Note 3 got it right. But it took twice the cores, clocked at twice the speed with three times the memory ( ⅔ to ¾ of which is in use even without an app running! I've got one though and don't take me wrong, I love it) to get 'close' to the GUI fluency of the iPhone & iOS
    That's. SAD. That's. Buggy. I'd much rather have a phone that bends with a hundred pounds of torque in a certain and specific area than I would gambling I'll get an update, deal with carriers and OEM bloat and shitty aesthetics and design. Lack of support or resale, lack of apps and software ...& the apps and software in parity are incredibly more enjoyable and stable on iOS. I like my Note for browsing and the SPen. I think an active digitizer would put the six plus over the top but as it is, it's perfect.
    Indeed, I'll continue using (& owning) my N3. But I'm not the least bit compelled with the '4' and its 2540 display. While I'm sure there's noticeable and 'obvious' benefits to having 550/600+ PPI ...I'll warn ya when you're 38-42, speaking from experience...you'll need 'cheaters';) ...like our ears, our eyes deteriorate as well ...the elasticity of our lens and ability to change and 'maintain' up close focus just ...goes away! Hence the incredible benefits I've found witg the HiDPI display technology. 3D? Good riddance! It was a joy to see 4k/Ultra HD and even examples of 5/6 & 8K motion display AND capture gear instead of dumbass glasses and crappy off center viewing with limited content.

    Apple lead the way and destroyed multi billion dollar monsters in the industry with the iPhone. They then changed consumer display technology's availability. HiDPI and increased resolution is awesome. But to a certain point. Your 1080p 65" LED LCD IPS or AMOLED TV in the living room at 10-12 feet or typical viewing distances is around 100ppi. Quadrupling the resolution (4k) while not exactly linear, will amount to approximately an increase of 100%. To 200ppi. Not four foukd as you may think.
    The 'new' ipad(3)/4 -- iPhone 4 -- the rMBPs --- ALL Game Changing home runs. Putting a certain 'joy' back into 'work' again. With SUCH an accurate palate and the ability of OS X'es scaling of the UI (& third party apps the same ...utilizing pixel for pixel when necessary or quadrupling for the GUI simultaneously and without 'glitches' or latency is a marvel in engineering. Coupled with the IrisPro 5200/750m and PCIe SSD at a TB with read and write speeds exceeding a Gb/s, Thunderbolt 2 and its 'one' cable capabilities and abilities to run multiple 4K displays ...shoot man. Seems like yesterday I was hunting the wax pencils and cutting my fingers slicing tape ...now it's immediate and fast as hell in a four pound package at a dozen times the resolution.

    Times are good if you're an Apple user. And thats JUST the hardware!

    OS X and iOS's march to marriage is incredible. Continuity and Handoff. Air drop between iOS and OS X, as well ...the aggregation and integration between the devices you're using is revolutionary. Period. Only Windows has the power and support vertically and horizontally to compete with what Apple's doing. Vertical & Horizontal backbones.

    No one that needs to 'work' is buying a Chromebook

  • elajt_1 - Friday, October 3, 2014 - link

    This must've been the longest and weirdest Iphone ad I've ever read. ;-)
  • techconc - Monday, October 6, 2014 - link

    @shm224 - I now know several people with iPhone 6 and 6+ devices that keep them in their pockets. They all seem to agree that there is no merit to this "bend gate" nonsense. While nobody doubts that these phones can bend under a certain amount of pressure (90 lbs. according to Consumer Reports), from a practical matter, it's a non-issue. Further, I find it rather interesting that phones such as the HTC One which bend under significantly less pressure (70 lbs.) don't receive the same sort of media attention.
    As for the 8.0.1 update, yup, Apple screwed that up. Fortunately, for Apple, the update was pulled after about an hour. It's also fortunate that in only affected some phones and only for the over the air update as opposed to the iTunes update. To your point, no, this typically isn't an issue for other phones... then again, neither are regular updates.

Log in

Don't have an account? Sign up now