Conclusion & End Remarks

While the iPhone XS and XS Max in one sense are just another iteration on last year’s iPhone X, they’re also a big shift for Apple’s line-up. Rather than being actual successors to the iPhone 8 and 8 Plus they're closer to next-generation replacements, but with some significant differences. In that respect I do regret missing out on the iPhone XR for this review, as I think it’s going to be an incredibly attractive alternative to the XS models.

Design wise, there’s not much to talk about the XS: the smaller variant is nigh identical to the iPhone X, with the only visual differences between the phones being the added antenna lines on the XS, virtue of the new 4x4 MIMO cellular capabilities of the phones.

The XS Max sports Apple’s biggest screen, and in a sense I do like the design more because it does have a bigger screen-to-body ratio. Apple’s bezel design is intentional, but I did hope they had shaved 1-2mm off the sides, as I’ve gotten used to other, more full-screen devices. One thing to consider about the XS Max, is that’s it’s really heavy for a phone, passing the 200g mark at 208g.

The screens of the XS and XS Max are the best displays among any devices on the market: While Samsung still has a density advantage, the Apple phones just outgun competing phones in terms of colour accuracy and picture quality. The 10-bit panel allows seamless colour management between sRGB and Display P3 modes depending on content, and Apple’s still the only vendor able to do this without having significant drawbacks.

The Apple A12 is a beast of a SoC. While the A11 already bested the competition in terms of performance and power efficiency, the A12 doubles down on it in this regard, thanks to Apple’s world-class design teams which were able to squeeze out even more out of their CPU microarchitectures. The Vortex CPU’s memory subsystem saw an enormous boost, which grants the A12 a significant performance boost in a lot of workloads. Apple’s marketing department was really underselling the improvements here by just quoting 15% - a lot of workloads will be seeing performance improvements I estimate to be around 40%, with even greater improvements in some corner-cases. Apple’s CPU have gotten so performant now, that we’re just margins off the best desktop CPUs; it will be interesting to see how the coming years evolve, and what this means for Apple’s non-mobile products.

On the GPU side, Apple’s measured performance gains are also within the promised figures, and even above that when it comes to sustained performance. The new GPU looks like an iteration on last year’s design, but an added fourth core as well as the important introduction of GPU memory compression are able to increase the performance to new levels. The negative thing here is I do think Apple’s throttling mechanism needs to be revised – and by that I mean not that it shouldn’t throttle less, but that it might be better if it throttled more or even outright capped the upper end of the performance curve, as it’s extremely power hungry and does heat up the phone a lot in the initial minutes of a gaming session.

On the camera side, Apple made some very solid improvement all-around. The new sensor’s increased pixel size allows for 50% more light sensitivity, but the improved DTI of the sensor also allows for significantly finer details in bright conditions, essentially increasing the effective spatial resolution of the camera. SmartHDR works as promised, and it’s able to produce images with improved dynamic range. The telephoto lens is the one use-case where the XS really stands out over the iPhone X as exposure and colour rendition are significantly improved, one of the weak points of many telephoto cameras nowadays. Overall in daylight, the new iPhone is easily among the best smartphone cameras on the market.

In low light the iPhone XS also sees a big improvement, however it’s not enough to quite match Samsung’s hardware and Huawei’s processing. I do hope Apple will make use of the newfangled computational photography in more use-cases, as we’re seeing some great innovation from the competition in this regard.

Video recording of the iPhone XS is also a major improvement of the phone. From better dynamic range, better stabilisation, to better and now stereo audio recording, Apple makes a significant leap in the video performance of the new iPhones.

In terms of battery life, it was surprising that the iPhone XS wasn’t much of an upgrade over the iPhone X in our test. I’m still not sure if this is something related to some sort of hidden inefficiency of the A12, or maybe something to do with the new WiFi or cellular modem. For the latter, we’ll be revisiting the topic shortly, and to also re-validate the battery life numbers of this review.

For the iPhone XS Max, I wasn’t surprised to see battery life be less than on the iPhone 8 Plus – the OLED screen is less efficient than the LCD display of last year’s phone – and the increased battery capacity is not enough to counter-act this. It’s just something to keep in mind for the big-phone users out there eyeing the iPhone XS Max in particular.

Overall, are the new iPhones worth it to upgrade to? If you’re an iPhone X user, I think my answer is no. If you’re coming from an older device, then my answer is… wait it out. When having a hands-on with the XR at the keynote event, my first thought was that this would be the model that would see the most success for Apple this generation. The problem here is that Apple is asking for a lot of money – if you’re entrenched in the iOS ecosystem, I think it’s best to evaluate the individual pros and upgrades that the new iPhone XS brings over your current device.

The value proposition aside, the new iPhone XS and XS Max are, as always, extremely polished devices, and the best phones that Apple has released to date.

Camera Video Recording & Speaker Evaluation
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  • Andrei Frumusanu - Friday, October 5, 2018 - link

    Pixels and Mate 20 are next in line.
  • name99 - Friday, October 5, 2018 - link

    Hi Andrei,

    A few comments/questions.

    - the detailed Vortex and GPU die shots seem to bear no resemblance to the full SoC die shot. I cannot figure out the relationship no matter how I try to twist and reflect...

    Because I can't place them, I can't see the physical relationship of the "new A10 cache" to the rest of the SoC. If it's TIGHTLY coupled to one core, one possibility is value prediction? Another suggested idea that requires a fair bit of storage is instruction criticality tracking.

    If it's loosely coupled to both cores, one possibility is it's a central repository for prefetch? Some sort of total prefetching engine that knows the usage history of the L1s AND L2s and is performing not just fancy prefetch (at both L1s and L2s) but additional related services like dead block prediction or drowsiness prediction?
  • Andrei Frumusanu - Friday, October 5, 2018 - link

    The Vortex and GPU are just crops of the die shot at the top of the page. The Vortex shot is the bottom core rotated 90° counter-clockwise, and the GPU core is either top left or bottom right core, again rotated 90° ccw so that I could have them laid out horizontally.

    The "A10 cache" has no relationship with the SoC, it's part of the front-end.
  • name99 - Friday, October 5, 2018 - link

    OK, I got ya. Thanks for the clarification. I agree, no obvious connection to L2 and the rest of the SoC. So value prediction or instruction criticality? VP mostly makes sense for loads, so we'd expect it near LS, but criticality makes sense near the front end. It's certainly something I'm partial to, though it's been mostly ignored in the literature compared to other topics. I agree it's a long shot, but, like you said, what else is that block for?
  • name99 - Friday, October 5, 2018 - link

    "The benchmark is characterised by being instruction store limited – again part of the Vortex µarch that I saw a great improvement in."

    Can you clarify this? There are multiple possible improvements.
    - You state that A12 supports 2-wide store. The impression I got was that as of A11, Apple supported the fairly tradition 2-wide load/1-wide store per cycle. Is your contention that even as of A11, 2 stores/cycle were possible? Is there perhaps an improvement here along the lines of: previously the CPU could sustain 3 LS ops/cycle (pick a combination from up to 2 loads and up to 2 stores) and now it can sustain 4 LS ops/cycle?

    - Alternatively, are the stores (and loads) wider? As of A11, the width of one path to the L1 cache was 128 bits wide. It was for this reason that bulk loads and stores could run as fast using pair load-store integer as using vector load stores (and there was no improvement in using the multi-vector load-stores). When I spoke to some Apple folks about this, the impression I got was that they were doing fancy gathering in the load store buffers before the cache, and so there was no "instruction" advantage to using vector load/stores, whatever instruction sequence you ran, it would as aggressively and as wide as possible gather before hitting the cache. So if the LS queue is now gathering to 256 bits wide, that's going to give you double the LS bandwidth (of course for appropriately written, very dense back to back load/stores).

    - alternatively do you simply mean that non-aligned load/stores are handled better (eg LS that crossed cache lines were formerly expensive and now are not)? You'd hope that code doesn't do much of these, but nothing about C-code horrors surprises me any more...

    BTW, it's hard to find exactly comparable numbers, but
    https://www.anandtech.com/show/11544/intel-skylake...
    shows the performance of a range of different server class CPUs on SPEC2006 INT, compiled under much the same conditions. A12 is, ballpark, about at the level of Skylake-SP at 3.8 to 4GHz...
    (Presumably Skylake would do a lot better in *some* FP bcs of AVX512, but FP results aren't available.) This gives insight across a wider range of x86 servers than the link Andrei provided.
    The ideal would be to have SPEC2006 compiled using XCode for say the newest iMac and iMac Pro, and (for mobile space) MacBook Pro...
  • Andrei Frumusanu - Friday, October 5, 2018 - link

    > Is your contention that even as of A11, 2 stores/cycle were possible?

    Yes.

    > - Alternatively, are the stores (and loads) wider?

    Didn't verify, and very unlikely.

    > - alternatively do you simply mean that non-aligned load/stores are handled better

    Yes.
  • remedo - Friday, October 5, 2018 - link

    Can you please review the massive NPU? It seems like NPU deserves a lot more attention given the industry trend.
  • Andrei Frumusanu - Friday, October 5, 2018 - link

    I don't have any good way to test it at the moment.
  • Ansamor - Friday, October 5, 2018 - link

    Aren't these (https://itunes.apple.com/es/app/aimark/id137796825... tests cross-platform or comparable with the ones of Master Lu? I remember that you used it to compare the Kirin 970 against the Qualcomm DSP.
  • Andrei Frumusanu - Friday, October 5, 2018 - link

    Wasn't aware it was available on iOS, I'll look into it.

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