The Apple iPhone 6s and iPhone 6s Plus Review
by Ryan Smith & Joshua Ho on November 2, 2015 8:00 AM EST- Posted in
- Smartphones
- Apple
- Mobile
- SoCs
- iPhone 6s
- iPhone 6s Plus
Dual Sourcing A9: Two for the Price of Two
Perhaps more remarkable than the fact that the A9 is built using a FinFET process however is who it is being built by. For the first time Apple is dual sourcing the SoC – rather than using TSMC or Samsung exclusively, they are using both.
Broadly speaking, dual sourcing is a practice that has fallen out of style as the number of contract semiconductor manufacturers has dwindled and the cost of chip production has gone up. Because each manufacturer has its own rules and own best practices, to dual source a chip involves designing it twice, once for each manufacturer. This has made the cost of dual sourcing increase over time, and consequently dual sourcing falling out of fashion.
This of course is a big part of what makes Apple’s decision to dual source so unexpected. Apple is taking a much bigger gamble this time around by dual sourcing than they have on past SoCs where it was produced by a single manufacturer (be it TSMC or Samsung). Dual sourcing means that Apple’s costs to tape-out and bring-up A9 have very nearly doubled; they have to tape-out each version of the A9 for the respective fab’s rulesets, and then they have to go through the bring-up process with each in order to dial-in the yields and clockspeeds. They at least get to reuse the underlying architecture (e.g. Twister CPU and their PowerVR GPU), but actually creating a chip design for each fab is a significant part of the development costs for A9.
Samsung vs. TSMC A9 Die Size (Image Courtesy Chipworks)
The end result then is two similar but not quite equal chips that are produced by TSMC and Samsung respectively. Both are A9s, both feature the same CPU, GPU, memory interface, and all of the other bits that make up an A9. But each is produced at a different fab, according to the rules of that fab.
One of the immediate ramifications of dual sourcing is that the die sizes of the A9s are different. The A9 produced by Samsung on their 14nm FinFET Process is the smaller of the two, at 96mm2. Meanwhile the A9 produced on TSMC’s 16nm FinFET process is 104.5mm2, making it about 9% larger. Though not an immense difference in size (and not that we’d expect otherwise) there are tradeoffs to be had. With all other things held equal, the larger TSMC die would produce fewer complete dies per 300mm wafer, and any given die is more likely to have an imperfection since there are fewer dies for the same number of imperfections. This gives the Samsung A9 a slight edge in manufacturing thanks to its better density, however it’s equally important to note that in the real world there are a number of factors at play here, including manufacturing yields at each fab and how much each fab is charging Apple, so while the Samsung A9 is the smaller A9 it isn’t necessarily the cheaper A9.
The bigger question on many minds is whether there’s a performance difference between the two A9s. We wrote a bit on the subject a few weeks back, and the short answer is that it’s very difficult to tell. Due to chip quality being a distribution no two phones utilizing the same A9 are the same, and that means just comparing any two phones can’t tell us the whole story. Ultimately what one needs is a large number of phones to find the distribution, the median of that distribution, and how the medians compare. This is something that if done perfectly would require thousands of phones, and is really only possible for Apple or the competitive analysis teams at their well-funded competitors.
Apple A9 Die Shots (Image Courtesy Chipworks Teardown Report)
At this point then we don’t have anything new to add to the discussion – we don’t have enough data – though it is still a matter we are working on. Sometimes the best thing we can do is say is when we don’t have enough information, rather than extrapolating too much from too little information. I will note however that it’s ultimately in Apple’s best interests for the A9s to be as similar as possible, and there are steps they can take to ensure that, particularly in selecting which chips they will use.
Current A9 Chip Manufacturer Distribution (Image Courtesy Hiraku)
Meanwhile looking at the data collected by iOS developer Hiraku’s CPU Identifier project, it’s interesting to note that of the 250K+ phones sampled so far, the Samsung A9 is in 63% of those phones, giving us a Samsung-to-TSMC ratio of nearly 2-to-1. This survey should not be considered the final word in the ratio between the two A9s since it can change over time and an opt-in survey of this fashion has an inherent self-selection bias, but with so many results it should be a reasonably accurate summary of the current situation.
What remains to be seen – and likely never to be answered outside the walls of One Infinite Loop – is why Apple dual sourced in the first place. We can certainly speculate on reasons they would do this – yield issues at a fab, a desire to avoid putting all of their eggs in one basket and giving one fab too much power, or even just wanting to ramp up A9 production quickly by doubling the number of fabs working on it. What is apparent however is that with Apple selling 48M iPhones in Q3’15 (note that the majority of these were not 6ses), A9 is a uniquely good candidate for dual sourcing. Apple sells enough iPhones that their large pile of cash aside they can absorb the cost of dual sourcing by spreading out the costs over tens of millions of high-margin chips, and if yields/supply were a factor in this decision then that’s all the more reason to dual source. This in turn makes me wonder if we’ll see Apple continue this strategy given their enormous volume, or if this was a one-time event due to the early nature of FinFET, leading to them settling on a single fab for the iPhone 7 launch.
Die Size: Hitting the Sweet Spot
Finally, before jumping into our discussion of the A9’s CPU and GPU, let’s talk about A9’s die size in a historical context. Unlike the transition from A7 to A8, Apple doesn’t get the advantage of a substantial transistor density improvement going from A8 to A9. To use TSMC as an example here (since they produced A8), their 16nm FinFET process is advertised as having 2x the density as their 28nm process, however compared to that same 28nm process their 20nm process had a 1.9x density advantage. In other words, the transition from 20nm HKMG planar to 16nm FinFET does not bring with it the same kind of density improvements we’ve seen in the last few generations.
In fact the only other time Apple has not had the advantage of a density improvement is the transition from A4 to A5, which saw Apple’s die sizes transition from what remains their smallest die to their largest die, all in a single generation. For A9 then Apple has to work smarter, as they can’t add a large number of transistors relative to A8 without ballooning A9’s die size outside of Apple’s sweet spot (and harming chip yields at the same time).
| Apple SoC Evolution | |||
| Die Size | Transistors | Process | |
| A5 | 122m2 | <1B | 45nm |
| A6 | 97mm2 | <1B | 32nm |
| A7 | 102mm2 | >1B | 28nm |
| A8 | 89mm2 | ~2B | 20nm |
| A9 | 96mm2/104.5mm2 | >2B | 14nm/16nm |
Consequently the A9s that we’re getting are surprisingly conservative. The TSMC A9 is 104.5mm2, some 17% larger than the TSMC A8. Meanwhile the Samsung A9 is the smaller of the two at 96mm2. The TSMC A9 is now Apple’s second-largest non-X SoC, but just barely so; it’s only 2.5mm2 larger than the A7. Otherwise with an average die size of 100mm2, this puts the A9 at the upper-bounds of Apple’s sweet spot.
Yet despite the limited gains in transistor density versus A8, Apple has managed to “bulk up” their SoC design by quite a bit. We’ll go over this in greater detail on the following pages, but of particular note is that Apple is now implementing what we believe to be a 6 core PowerVR GPU design, and Apple has significantly increased both the L2 and L3 cache sizes. Coupled with this is the jump to LPDDR4 (requiring more complex memory controllers) and numerous smaller improvements we’ll likely never learn about. The number of CPU cores remains unchanged at 2 however.
Chipworks' Initial Layout Analysis (Image Courtey Chipworks)
My Layout Analysis For A9 (Die Shot Courtesy Chipworks)
On a final note, now that we have die shots of both A9s from Chipworks, I must tip my hat towards Apple for releasing an accurate die shot of what we now know is the Samsung A9 in their iPhone 6s presentation. Up until now Apple has never released their own die shot of their SoCs, and in fact first-party die shots are becoming increasingly rare as a whole in the semiconductor industry. Consequently I had expected that Apple’s die shot was a fake, only to be far more impressed that it’s real. Furthermore despite the low resolution of the shot, Apple’s false color and contrast enhancements make it surprisingly clear where the CPU and GPU blocks are, and how many of each there are. This is a level of contrast that even the Chipworks shots can’t quite match this time around.
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akdj - Tuesday, November 3, 2015 - link
Hi Josh and Ryan,Many, MANY thanks for the insight and in depth review. I've just finished my second read (it was late last night I noticed the review and read through) and your experiences mimic mine. With a single exception. I'm a business owner, have been over 26 years now and use phones for the business and personal. I also outfit employees so I have a chance to stay 'ambidextrous', keeping a foot in Android, rest of the body in iOS ... But some things I do enjoy on both my older Note 4, & newer S6. No intrigue with the Note 5 other than its SoC, speed of internal storage and design over my older N4. As an S6 Edge owner I'm well aware of the speeds uninstalling, installing apps, opening them, the 'feel" of the newer 2015 Sammy phones as well as the exceptional speed of the Exynos processor. That said, you made a remark I don't quite agree with
"The second generation of TouchID isn’t quite as life-changing, but it’s a welcome improvement nonetheless. Again, this is a case where there was friction in the user experience that wasn’t really noticeable until it was gone. Obviously, Apple is no longer the only one at this level of user experience with fingerprint scanners but they are keeping up."
I'm not sure which phone you've found that parities the iPhone 6s/6+s for FP register. As it's certainly not the S6/S6+/Note 5 or LG (I've got one of their freebie 8" LG tabs from AT&T runnin LP). I'm hoping anyway lol. My silly S6 is just finally starting to correctly register 50% of the time with the 5.1 update. The previous six months I was lucky to have my thumb recognized 1 of 5 times. And it's registered as FOUR different 'fingers'.
I'm also an owner of the 6+s and even checking the time or setting an Altman, turning the flashlight on, etc...it's so damn quick, I'm automatically on the home screen. It's ...pardon the pun, lightning fast and immediate. I guess I'm curious as to which OEM Apple is keeping up with as I had the 5s and 6+ standard as well. The Note 4 is a useless implementation and the S6, while better is a LONG way off from 'keeping up with...' Apple again IMHO. Genuinely curious as to the OEM making better or even similar performing and 'protective' measures than Apple.
Other than that silly nitpick, I agree completely and haven't enjoyed an iPhone as much since the iPhone 4 and its HiDPI display. If I recall, another 'first', wasn't it? (Like the 5s FP reader, actually able to 'read an FP ;)). Maybe it's my aging mid 40s eyes but the higher resolutions and larger displays have literally kept pace with my deteriorating vision!
Once again, many thanks for the perfectly balanced nerd/everyday 'Joe n Jane' subjective review of 'real world use'. Always refreshing to hear... I mean read your reviews, un-rushed to keep up with the herds the day after release or a week post NDA, minus the carrying around and using ...or simple resolution, 100% 'chart n number' reviews.
Loved it. And I'm loving the iPhone 6s+. It's truly a computer in my pocket. I know you briefly touched on the expanded radios both WiFi and LTE, another maybe at first unnoticeable unless ...again as you mention an iCloud restoration of significant size, but a HUGE end user boon. These are incredibly fast, seemingly more 'stable' in 5MHz mode. (Maybe a bad word, stable but hard to put my finger on it, as older modems on the iPhone with AC/5MHz or is it GHz? Now I'm lost. This one seems faster, more efficient and stable than earlier versions )
My wife has an identical iPhone 6+s. 128. Hers is Sammy mine TSMC. Neither has shown any significance in battery draw than the other. Mine measures 2238/4437 in GBench, hers 2242/4405 after six runs ...that's the mean. Power and efficiency are nearly identical after a weekend at our cabin we both had single digit %'s and used them nearly the same the entire weekend.
Very VERY great phone
J
MarcSP - Wednesday, November 4, 2015 - link
Thanks for your explanation :-). Still, I think there must be something else. I mean, most Samsung phones also use amoled and did not get such a low score in browsing, and the Snapdragon 800 is not a very slow SoC. Even today there are many low and even middle-end phones sold with weaker SoC.zodiacfml - Wednesday, November 4, 2015 - link
i dont like apple but their engineering and design is very impressive. i wonder how the new cpu compares to a Core M.tharun118 - Wednesday, November 4, 2015 - link
The best phone? Seriously? I've seen a lot of people saying iPhone as THE BEST phone, but AnandTech? Come on.. I believe that there can never be a "THE BEST phone". Yes, iPhone 6+ has a very good SoC, reliable camera, 3D Touch, etc, but like every flagship phone, there are compromises and drawbacks. For me, I choose a smartphone based on 4 major aspects. First, the screen. I know Apple lovers always defend their 320+ PPI screen saying that's more than enough and they don't need anything more. But the truth is, they are far behind Samsung and that will likely change in 7 or 7s. Second, the camera, this is purely subjective, there are people who'd prefer photos from an iPhone and there are people who'd prefer photos from 2015 android flagships (S6, Note 5, G4, 6P, etc). Third, battery and performance: Apple is better here on a tiny margin due their vertical integration. I think Android phones will never reach the exact smoothness in performance and efficiency in power consumption of the latest iPhone, due to fragmentation. Fourth, customisation: No comments here, but I understand there are lots of people who'd happily use their phone the way their manufacture tells them to. I'm definitely not one among them. I try to balance all these 4 aspects and my choice this year was a Galaxy S6. Of course, there are bonus features such as, wireless charging, quick charge (very useful), IR port, etc. But still, I wouldn't call S6 as THE BEST. Neither is an iPhone 6+.Vincog - Wednesday, November 4, 2015 - link
I got iphone 6S with samsung chip here, and my battery will decrease 1% every 5 minute in use or 1% every 15 minute standby... ( take a note all background refresh off, location off, only hey siri on ) ..Even my iphone 5s is more better than this one!! 😭😭😭😭Tigran - Wednesday, November 4, 2015 - link
***Looking at GFXBench, which is an infinite loop of the T-Rex on-screen benchmark to approximate intensive video gaming we see that the iPhone 6s doesn’t last very long either, but the performance throughout the test is incredible. Due to 1334x750 display resolution and strong GPU, the iPhone 6s manages to last the entire test without any notable throttling, and effectively pegged at the refresh rate of the display.
***
Why V-Sync (which limits T-Rex on-screen by 60 fps) is ignored? And what about this throttling evidence (by 20-22% in GFXBench off-screen):
http://forums.anandtech.com/showpost.php?p=3772777...
blackcrayon - Wednesday, November 4, 2015 - link
They mentioned that the 6s+ throttled slightly due to the higher resolution, so it stands to reason that the 6 would also throttle when rendering a higher resolution offscreen. But it's nowhere near the throttling of any of the competitors, games are still remaining playable throughout a reasonable gaming session.Tigran - Wednesday, November 4, 2015 - link
You don't get it. It's not about resolution - it's about T-Rex on-screen which limits performance to 60 fps. Without this limit iPhone 6s performance would be much higher, so it is incorrect to mention T-Rex on-screen discussing iPhone 6s throttling. If there is throttling, it can decrease from 100 to 70 fps, but you will see only 60 fps during the whole test - because of V-Sync. And there is evidence off throttling in Manhattan (which doesn't reach 60 fps limit) actually - see my link above (20-22% throttling). I can add that popular Russian laboratory (overclockers.ru) tested throttling of iPhone 6s via Basemark Metal, and they found enormous throttling there - from 911 down to 525 (74%).zhiliangh - Wednesday, November 4, 2015 - link
Thank you! I have been waiting for your review before upgrading any phone this year. This is a must-read iphone review.Spunjji - Wednesday, November 4, 2015 - link
I have a bit of a gripe regarding the conclusions in the camera section. The LG G4 is clearly providing better images at night than the iPhone 6s and 6s Plus - granted there is "less motion blur" in the Apple images, but they're also quite clearly underexposed by at least a stop. It therefore seems odd to conclude that a product which produces grainier, less-detailed and murkier images than the competition is better. You could produce similarly non-blurry results on the G4 by adjusting exposure compensation and then have the best of both worlds!