Apple iPhone 6 And iPhone 6 Plus Review

Why you can trust Tom's Hardware Our expert reviewers spend hours testing and comparing products and services so you can choose the best for you. Find out more about how we test.

Apple’s A8 SoC: GPU And The Uncore


Over the past few years we’ve gotten used to Apple announcing that its new chips get twice as much graphics performance compared to the previous generation. This year, Apple broke that trend and announced only a 50-percent improvement over the PowerVR G6430 inside its A7 SoC. This improvement is inline with what Imagination promised at CES this year when it announced the new PowerVR Series6XT GPUs. The direct successor to the PowerVR G6430 is the PowerVR GX6450, which has the same number of clusters (four), while the clock speed is unknown at this time.

Because Apple increased the pixel count of its iPhone 6 Plus by almost three times compared to the iPhone 5s, many were expecting the beefier PowerVR GX6650, Imagination’s top-of-the-line mobile GPU. It would have yielded the expected 2x increase in performance over the previous generation, and it would’ve also made the transition to a 1080p phone easier (at least in terms of gaming performance at native resolution).

Apple must have determined that the performance of a PowerVR GX6450 GPU would be more than enough for the iPhone 6 Plus, considering the weaker PowerVR G6430 powered its 2048x1536 iPad Air last year. Apple is likely using the GX6650 in its A8X SoC and using it as a selling point for the iPad Air 2.

(Image credit: Imagination Technologies)

Although Apple promised a 50% performance improvement, most benchmarks fall short of that value. This year, Apple seems to be focusing even more than usual on battery efficiency, so it’s possible the company kept the clock speeds lower than necessary to reach Imagination’s promised speed-up. Apple is also pushing developers to use the Metal API, so it may be betting on Metal adoption to reach that performance increase.

Imagination’s Series6XT is an iteration of Series6, but it does come with a few new features, such as improved support for OpenGL ES 3.0 (OpenGL ES 3.1 support seems to be lacking right now), support for next-generation ASTC texture compression with fine-grained quality options and improved power management.

Khronos is pushing for ASTC as a universal texture compression format that it hopes all GPU makers will adopt. Although the Khronos Group hasn’t made ASTC support mandatory yet, it seems new GPUs from different companies are starting to support it, and it could be widely supported by all GPU makers in a few years anyway.

The new “PowerGearing G6XT” feature allows individual clusters to power down or spin up when needed, thus improving power consumption for idle or light usage, where all clusters may not be utilized.

Overall, the PowerVR GX6450 seems to be sufficient for the iPhone 6, and even the iPhone 6 Plus, considering the previous GPU could handle even higher resolutions quite easily. If developers take advantage of Apple’s Metal API (possibly to the detriment of cross-platform portability) they might be able to squeeze a little more performance out of it for gaming, and show the iPhone 6 users more impressive graphics than what they’ve seen before on their older iPhone 5s devices.

More Uncore

The CPU, GPU and L3 cache only account for roughly half of the overall die area, the remainder occupied by memory interfaces, I/O, DSPs and various fixed-function hardware. It’s in this area of the SoC that Apple uses some of those extra transistors. One of the new features for the iPhone 6 and 6 Plus is High Efficiency Video Coding (HEVC) for FaceTime video calls over cellular. Since this feature is exclusive to iPhone 6, it implies that the A8 includes a fixed-function H.265 encoder/decoder, which may cut bandwidth requirements in half.

Last year, alongside the A7, Apple introduced its M7 motion coprocessor. The M7 is a Cortex M3-based microcontroller from NXP Semiconductors, labeled LPC18A1, that has been customized by Apple to collect and process data from the accelerometer, gyroscope and compass in a battery-friendly way, feeding its data to fitness apps.

The new iPhones receive an improved M8 coprocessor that tracks barometer data from a new sensor. It may also be based on Cortex M3 (rather than Cortex M4) going by its very similar name: LPC18B1. NXP has also named its Cortex M4-based microcontrollers to the LPC4300 family, so it’s even more likely Apple stuck with the older microcontroller.

  • manez
    I can think of a thousand more interesting things to review than the newest iphone x.
  • blackmagnum
    Everyone would want to own one and be the envy of their peers. They want a device that is attractive, well-made and intuitive. That's how Apple sells them by the millions, don't you agree?
  • lanbaner
    Nvidia has a better GPU. The G3 has a better display. The Note 4 has better camera. Gone are the days were the iPhone was the leader on all fronts. Would be nice to see all the strengths from the competition in one phone. Considering the transition to 20nm for Maxwell early next year we could possibly see an iPhonekiller on all aspects. Although I have to agree that the build quality on the iPhones is always top notch.
  • M3God
    Other then just sticking to just 1GB internal memory, there is no mention that apple switched to cheaper and slower TLC memory to make more profits while screwing the customer. The TLC memory has been linked to crashes and bootloops that require a trip to the apple store.
  • aaaas
    I browse the Web and talk on the phone on Verizon all the time. At least the last two generations of devices have been able to do this... at least for android...

    Interesting article, as I've been considering a switch to iphone.
  • KaptainK
    " Wi-Fi calling is currently only supported by T-Mobile in the U.S."

    Not True! Republic Wireless has been using wi-fi calling for years. Republic also includes a feature where it will hand the call off from wi-fi to cellular if you leave the wi-fi zone during the call. Does the iPhone do this??
  • cknobman
    A. Thanks for including the Lumia 1520 in the comparison chart of phablets, most other sites dont do this.

    B. The price for the 6 plus in that same chart ($299) is on contract while every other device price is off contract.

    As a whole if you are an iPhone user I am sure you are happy with the changes made to the 6. Outside of that the iPhone "cool factor" ship has sailed and this wont be winning over many Android users.
  • cmi86
    How can this guy sit here and hump apples leg by saying the A8 should be competitive if not class leading when it's competition averages over 1Ghz higher clock speed and 2 more cores.... I know a lot of people doing reviews now a days feel obligated to shine up certain companies and make their products appear in a positive light. This is not that... this is a blatant lie.
  • SirKnobsworth
    How can this guy sit here and hump apples leg by saying the A8 should be competitive if not class leading when it's competition averages over 1Ghz higher clock speed and 2 more cores.... I know a lot of people doing reviews now a days feel obligated to shine up certain companies and make their products appear in a positive light. This is not that... this is a blatant lie.
    Clock speeds and core counts can be deceptive, the key point here being that Apple's Cyclone cores can execute about twice as many instructions per clock cycle as most of their competitors. This shows up in the benchmarks - the iPhone 6 and 6+ do very well in single threaded tests, though tend to lag behind competitors in multithreaded tests like physics. Note that this is also the approach that Nvidia is taking with their Denver cores - fewer, bigger cores as opposed to more small cores.

    How this translates into actual performance will vary of course - most smartphone workflows aren't particularly well threaded so having four cores as opposed to two probably won't make a huge difference in many situations, but I'm sure there are plenty of exceptions.
  • ZXS
    Due to their zero reading on the black level tests, AMOLED displays are said to have an infinite contrast ratio.

    MATT, do you know this is Samsung's marketing BS?

    Smartphone displays reflect about 6% of incoming light (which is much more than LCD backlight emits). Actual contrast of AMOLED is worse than that of LCD since the reflections are so high, but maximum brightness is much lower than that of LCD.