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
A9's GPU: Imagination PowerVR GT7600
With so much time spent talking about A9 from the perspective of its manufacturing process and its Twister CPU, it’s all too easy to forget that Apple has been working on far more under the hood than just CPU performance. As has been the case for generations now, Apple continues to focus on GPU performance, laying the groundwork for significant performance improvements with every generation.
Going all the way back to the first iPhone and its Samsung-developed SoC, Apple has been a patron of Imagination Technologies and their PowerVR GPUs. This has been a productive relationship for both parties, and for A9 this hasn’t changed. To no surprise then, the GPU in the A9 is another design in Imagination’s PowerVR Rogue family, the GT7600.
Briefly, while Apple continues to not disclose the GPU used in their designs – referring to the A9’s GPU as iOS GPU Family 3 v1 – a look at the iOS Developer Library makes it clear what GPU family is being used. Apple still uses tile-based deferred rendering GPUs (to which only PowerVR fits the description), so the only real questions are which family is in use and how many cores are present.
With A8 and its GX6450, there was a pretty clear smoking gun to identify the GPU family via the inclusion of ASTC support, a feature only available on Series 6XT and newer GPUs. There aren’t any such smoking guns on the A9, but the Metal Feature tables indicate that there are a handful of new low-level features which are indicative of a newer revision of the PowerVR Rogue architecture. Coupled with the fact that Imagination announced PowerVR Series 7 nearly a year ago and Apple has proven to be able to implement a new PowerVR design in under a year, and it’s a safe bet that A9 is using a Series 7 design.
As for the configuration, the A9 die shot quickly answers that one. There are 6 distinct GPU cores on the A9 die, divided up into 3 pairs with a shared texture unit in between them. So it may have taken Apple a generation longer than I initially expected, but with A9 we’re finally looking at a 6 core GPU design for the iPhone.
From a feature and design standpoint then, the GT7600 is not a significant departure from the GPUs in the A8 and A7 SoCs, however it does have some notable improvements along with some optimizations to boost performance across the board. Notably, relative to the GX6450 it features a geometry tessellation co-processor as a base feature, a function that was merely optional on Series6XT and, at least in Apple’s case not used. Unfortunately, looking through Apple’s developer documentation it does not appear that tessellation support has been added for Metal, so assuming for the moment that Apple hasn’t stripped this hardware out, they definitely don’t have API support for it.
Otherwise the bulk of Imagination’s focus has been on small tweaks to improve the Rogue architecture’s overall efficiency. Among these, the Special Function Units can now natively handle FP16 operations, saving power versus the all-FP32 SFUs of Series6XT. SFU operations can now also be co-issued with ALU operations, which improves performance when SFUs are being issued (which in Imagination’s experience, has been more than expected). Finally, the Vertex Data Master (geometry frontend), Compute Data Master (compute frontend), and the Coarse Grain Scheduler have all been updated to improve their throughput, and in the case of the scheduler improving its ability to keep USCs from stalling on tile-interdependencies.
Looking at the broader picture, after initially being surprised that Apple didn’t jump to a 6 core design with A8, with A9 it makes a lot of sense why they’d do it now. GPUs have and continue to be the biggest consumers of memory bandwidth in high-performance SoCs, to the point where Apple has outfit all of their tablet-class SoCs with a wider 128-bit memory bus in order to feed those larger GPUs. Conversely, a 64-bit memory bus with LPDDR3 has always represented a memory bandwidth limit that would bottleneck a more aggressive GPU design. With the move to LPDDR4 however, Apple has doubled their memory bandwidth, and coupled with the larger L3 cache means that they now have the means to effectively feed a larger 6 core GPU.
Overall then, between the 50% increase in the number of GPU cores, Imagination’s architectural efficiency improvements, Apple’s own implementation optimizations, and what I don’t doubt to be at least a decent increase in the clockspeed of the GPU, Apple is promoting that A9 should see an incredible 90% increase in GPU performance relative to A8. And as we’ll see in our performance benchmarks, they are more than capable of delivering on that promise.
| Mobile SoC GPU Comparison | ||||||||
| PowerVR SGX 543MP3 | PowerVR G6430 | PowerVR GX6450 | PowerVR GT7600 | |||||
| Used In | iPhone 5 | iPhone 5s | iPhone 6 | iPhone 6s | ||||
| SIMD Name | USSE2 | USC | USC | USC | ||||
| # of SIMDs | 12 | 4 | 4 | 6 | ||||
| MADs per SIMD | 4 | 32 | 32 | 32 | ||||
| Total MADs | 48 | 128 | 128 | 192 | ||||
| Theoretical GFLOPS @ 300MHz |
28.8 GFLOPS | 76.8 GFLOPS | 76.8 GFLOPS | 115.2 GFLOPS | ||||
| Pixels/Clock | N/A | 8 | 8 | 12 | ||||
| Texels/Clock | N/A | 8 | 8 | 12 | ||||
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flyingfiddle - Wednesday, November 4, 2015 - link
Truly amazed and convinced that Apple has the best SoC of any phones, and their investment on the SoC paid off. So does their investment on refined iOS experience. I am Android guy but I have to admit I really wish SoC on Android could catch up one day, sooner the better.On the other hand, just because Apple is great in some areas does not mean they should get away with other things that's not as great. The raw power of a high end phone has become more than sufficient for many general users, such that making it more powerful is starting to generate diminished return. I could think of many things that I wish iPhone has, such as longer battery life (i know it's great, relatively, but why not push the boundary?), better screen/body ratio, external memory, more setting and better UI in the camera app, etc.
Well, still not my cup of tea but truly wish Android SoC could catch up one day. That's assuming Android platform survive that long (they have the largest market share but really don't make much money). I hope my money helps supporting them a bit longer..
tytung - Wednesday, November 4, 2015 - link
Can anyone comment on the iPhone 6s Plus frame rate dropping issue ? Animations looks choppy and the frame rate looks like only about 30 fps, unlike 60 fps on the 6s. If the GPU on the phone is so powerful this should not be an issue. In fact, for a phone this expensive UI frame rate drop is really a shameful problem.polmes - Thursday, November 5, 2015 - link
Got tired of iOS and moved to Android (Galaxy S6) earlier this year, but Apple definitely deserves an applause for being basically the only one to keep innovating in the mobile space. kudosSocius - Thursday, November 5, 2015 - link
Hmmmm...any idea why your iPhone 6s Plus scored just 15800 in Google octane when mine scored over 18,000? That's a pretty big discrepancy at 15%. Does your phone have a Samsung CPU? Mine is TSMC.zeeBomb - Thursday, November 5, 2015 - link
Both units are TSMC.Socius - Thursday, November 5, 2015 - link
Then there's something off as there is no way the 6s plus should be scoring just 15,800 on octane.mortimerr - Thursday, November 5, 2015 - link
I've never actually owned an Apple product in my life. All the way back to the original iPod classic. But I will probably finally be changing my stupid principle of 'No Apple Products'.The Android landscape recently has been going back instead of forward. Android 5-6 showcase minor improvements over 4.4.4 (Personally I also prefer Halo. Marshmallow and Lollipop looks slightly cartoony), battery life isn't that much of a leap (a lot of devices are experiencing the mobile radio active bug), and due to the fact that the high end market in the East is so saturated, most OEMs are cutting costs and putting out mid tier phones that lack top end hardware.
A lot of recent releases for Android have a great price point but either have a terrible camera (sensor, pixel size, post processing etc) or the IPS display leaves something to be desired, or it's this or it's that. The only OEM pushing the platform forward is Samsung. But, to be quite frank, I find those devices ugly to look at in every way from the bezel, UI skin, back, front, etc.
Where as Apple continues to simply improve with every iteration. Dual source fab at 14nm! What? 3D touch, increasing the ppi, maintaining solid battery life, great low light camera performance. Offering a big size and a small size with the same internals.
Sony also did this but I don't see the 810 as a very good chip going forward. Especially when it's already pretty far behind in performance to the Exynos and A#. I'll look forward to see if Sony updates the Z line.
I want to wait for Q2'16 for when devices with the 820 start being released, but what's the point when every device will inevitably have some drawback or large flaw or straight up just not be released in N. America.
JTRCK - Friday, November 6, 2015 - link
Where do you want phones to go? There's not much else they can do. A phone being imperfect is "always" the case. There is always something lacking in all these devices, including the iPhone 6S and 6S Plus. One of the first mentions in this review is that the author is still using an HTC One M7 from years ago. Because quite honestly, that was the pinnacle of smartphone design plus an excellent combination of fluid software, excellent performance, and an excellent night performance for a camera (though everything else about that camera was a downgrade). That 3 year old phone is still a very good performer today.Increasing processor/RAM/Storage speed is all excellent and it's expected, but the benefits from such increases are hardly felt by the user on day to day usage. Especially if the software is done properly. Example: I have an old iPhone 4s at home that I use for music streaming that consistently beat out my previous note 4 on application opening, multitasking, sound output quality, web surfing speed, etc. Which phone is superior? Which phone is better? Did AnandTech give that iPhone 4s the BEST award? In my view Apple has always been the king of software and hardware performance. They can get a device with 512mb of ram to outperform a Note 4 with a multicore processor and with 3GB of ram. They should always get the BEST award. But is the BEST (100%) really worth $1,200.00 when the second BEST (99%) is half the price?
I'm not talking about Samsung here. Their phones are expensive with crappy performance. I'm talking about the Moto X Pure, HTC One M9/10, Nexus 6P, etc. I used an iPhone 6S Plus for 2 weeks (and an iPhone 6 Plus for 4 months before that) and returned it for the Nexus 6P. I find the 6P to be a much better phone than the iPhone 6S plus in almost every aspect. It charges faster, it opens applications just as fast, I can multitask faster with the 6P with a side launcher without ever having to see a home screen. I can transition within an app at a faster pace due to dedicated back buttons. A simple thing as not having a "button" to go back a task annoyed me to no end with the iPhone. Not to mention all the limitations of iOS. The only benefit of iPhone for me were the integrations with my Macbook, but other than that. I disliked both iPhones.
The iPhone has all this amazing technology at its core, but my grandmother would never know when using her new 6S. And that's how it should be. I'm more amazed that a Nexus 6P costs half what an iPhone costs while still managing to do just as much, if not more. I honestly found nothing revolutionary about the 6S Plus while using it. In fact, I found it to be quite similar to the 6 Plus. Which I found to be quite similar to the iPhone 4s. Just much larger. And in terms of OS performance, vanilla android at this point is quite simply just as visually pleasing, power efficient, responsive and performant as iOS.
FL777 - Friday, November 6, 2015 - link
Amusingly, there is a YouTube real world speed test between the Nexus 6P and the iPhone 6S and the Nexus 6P BEATS THE IPHONE 6S!!!!!http://www.frequency.com/video/nexus-6p-vs-iphone-...
So much for the iPhone 6S SoC being unbeatable LOL.
Blark64 - Friday, November 6, 2015 - link
Umm, did you watch the video? The difference was milliseconds, and with a "hand-done" test like this the phones were well within the margin of error, and essentially tied. Also, that was possibly the least informative benchmark I've ever seen, since repeatedly launching apps in a tight cycle is something that essentially no one actually does in the real world. That's why benchmarks that are either: more reflective of the real world, or synthetic and scientifically repeatable (like Geekbench and the various browser benchmarks), are probably a better guide.