With their iPhone keynote behind them, Apple has begun updating some of their developer documentation for iOS to account for the new phone. This of course is always a fun time for tech punditry, as those updates will often include information on the hardware differences in the platform, and explain to developers the various features that different generations of hardware can offer developers.

To that end we have compiled a short analysis of the A8 SoC based on these documents and other sources. And we believe that at this point we have a solid idea of the configuration of Apple's latest SoC.

Apple SoC Specifications
  Apple A6 Apple A7 Apple A8
CPU Swift @ 1.3GHz(x2) Cyclone @ 1.3GHz (x2) Enhanced Cyclone @ 1.4GHz (x2)?
GPU PVR SGX543MP3 PVR G6430 PVR GX6650
RAM 1GB LPDDR2 1GB LPDDR3 1GB LPDDR3?

A8’s GPU: Imagination PowerVR Series6XT GX6650 GX6450

On the GPU front this year appears to be especially bountiful. After being tipped to an update for Apple’s Metal Programming Guide, we can now infer with near certainty that we know what the A8 GPU is.

New to this edition of the Metal Programming Guide is a so-called iOS_GPUFamily2, which joins the existing iOS_GPUFamily1. We already know that the iOS_GPUFamily1 is based around Imagination’s PowerVR Series 6 G6430 GPU, so the real question is what does iOS_GPUFamily2 do that requires a separate family? The answer as it turns out is ASTC, the next generation texture compression format is being adopted by GPU vendors over the next year or so.

Imagination’s PowerVR Series6 family of GPUs predates ASTC and as a result iOS_GPUFamily1 does not support it. However we know that Imagination added support for it in their Series6XT designs, which were announced at CES 2014. Coupled with the fact that Apple’s documentation supports the idea that all of their GPUs are still TDBR (and thus PowerVR), this means that the GPU in the A8 must be a Series6XT GPU in order for ASTC support to be present.

This leaves the question of which of Imagination’s 4 Series6XT Apple is using. Imagination offers a pair of 2 core designs, a 4 core design (GX6450), and a 6 core design (GX6650). Considering that Apple was already using a 4 core design in A7, we can safely rule out the 2 core designs. That leaves us with GX6450 and GX6650, and to further select between those options we turn to Apple’s A8 performance estimates.

Apple SoC Evolution
  CPU Perf GPU Perf Die Size Transistors Process
A5 ~13x ~20x 122m2 <1B 45nm
A6 ~26x ~34x 97mm2 <1B 32nm
A7 40x 56x 102mm2 >1B 28nm
A8 50x 84x 89mm2 ~2B 20nm

A8 is said to offer 84x the GPU performance of the iPhone 1, while last year Apple stated that the A7 offered 56x the iPhone 1’s performance. As a result we can accurately infer that the A8 must be 1.5x faster than the A7, a nice round number that makes it easier to determine with GPU Apple is using. Given Apple’s conservative stance on clockspeeds for power purposes and the die space gains from the 20nm process, accounting for a 50% performance upgrade is easily done by replacing a 4 core G6430 with the 6 core GX6650. At equal clockspeeds the GX6650 should be 50% faster on paper (matching Apple’s paper numbers), leading us to strongly believe that the A8 is utilizing a PowerVR Series6XT GX6650 GPU.

Once the iPhone 6 is out and Chipworks can photograph the SoC, this should be easy to confirm. If Apple is using a GX6650 then the die size of the GPU portion of the A8 should be very similar to the die size of the GPU portion of the A7. Otherwise if it is the 4 core GX6450, then Apple should see significant die size savings from using a 20nm fabrication process.

Update: The Chipworks die shots have confirmed that there are only 4 GPU cores present, not 6. So our earlier speculation was wrong; A8 is powered by GX6450, not GX6650

A8’s CPU: A Tweaked Cyclone?

Though we typically avoid rumors and leaks due to their high unreliability, after today’s presentation by Apple we have just enough information on A8’s CPU performance to go through the leak pile and start picking at leak. From that pile there is one leak in particular that catches our eye due to the fact that it matches Apple’s own statements.

On Monday night a supposed Geekbench 3 score of the iPhone 6 was posted. In this leak the iPhone 6 was listed as having a single-core score of 1633 points and a multi-core score of 2920 points. Curiously, these values are almost exactly 25% greater than the Geekbench 3 scores for the iPhone 5S (A7), which are 1305 points and 2347 points respectively.

The fact that ties all of this data together is that in their iPhone 6 presentation, Apple informed viewers that the iPhone 6 is 25% faster than the iPhone 5S. This data was later backed up with their latest CPU performance graph, which put the iPhone 6 at a score of 50x versus a score of 40x for the iPhone 5S.

Given Apple’s data, it looks increasingly likely that the leaked Geekbench 3 results for the iPhone 6 are in fact legitimate. The data leaked matches Apple’s own performance estimates, and in fact does so very well.

In which case we can infer a couple of points about the A8’s CPU, starting with the clockspeed. Given no other reason to doubt this data at the moment and given Apple’s preference for low clocked SoCs, the 1.4GHz reading appears legitimate. In which case this would be a 100MHz increase over the 1.3GHz A7 found in the iPhone 5S.

However the fact that it’s a 100MHz increase also means that clockspeeds alone cannot account for the full 25% performance gain that Apple is promoting and that these Geekbench results are reporting, as 1.4GHz is only a roughly 8% clockspeed increase over 1.3GHz. This in turn means that there must be more going on under the hood to improve the A8’s CPU performance other than clockspeed alone, which rules out a straight-up reuse of Apple’s Cyclone CPU.

Since Apple already had a solid ARMv8 architecture with Cyclone, there’s no reason to believe that they have thrown out Cyclone so soon. However this does strongly suggest that Apple has made some unknown revisions to Cyclone to further boost its single-threaded (Instruction Level Parallelism) performance. What those tweaks are remain to be seen as we would need to be able to benchmark the A8 in depth to even try to determine what Apple has changed, but for the moment it looks like we’re looking at an enhanced or otherwise significantly optimized version of Cyclone. And given Apple’s already high ILP, squeezing out another 16% or so would be a significant accomplishment at this time, especially for only a year’s turnaround.

1GB of RAM

Last but not least, the apparent validity of the Geekbench 3 leak means that one last piece of information on the A8 can apparently be confirmed: the earlier rumors about it being paired with 1GB of RAM are true. Unfortunately Apple’s official product image of the A8 is of no help here – it’s clearly a doctored version of the A7 image based on the product numbers attached – but this information is consistentwith earlier rumors based on leaked images of the real A8, which had also suggested the SoC contained 1GB of RAM. Again this is based on what we believe is a sound assumption that the Geekbench 3 leak is accurate since it so closely matches Apple’s own CPU performance estimates, but at this point we don’t have any substantial reason to doubt the data.


Image Courtesy Macrumors

The good news is that this is going to be the easiest aspect of the iPhone 6 to confirm, since diagnostic apps will be able to query the phone for the RAM amount. So one way or another we should know for sure come September 19th.

POST A COMMENT

136 Comments

View All Comments

  • lilo777 - Saturday, September 13, 2014 - link

    Obviously end users don't care where the improvements are coming from but that would mean that Apple were really misleading about GPU performance in their presentation. Reply
  • GC2:CS - Saturday, September 13, 2014 - link

    Series 6 XT offer 50% higher efficiency eg 50% higher performance at the same power plus 6650 would add another 50% thanks to being wider. They could just swap the 6430 for 6450 or they could also use the hexa-core and down clock it by 33% as lower clocked wider GPU is better in terms of power compustion, 20nm is not enough for 50% higher overall efficiency Apple is claiming.

    So far again the A8 looks like to be very focused on lowering the power comsumption which is extremely important in mobile business.
    Reply
  • darwiniandude - Tuesday, September 16, 2014 - link

    REALLY happy we're still going tk get articles like this and chip works teardowns after Anands departure. Keep up the good work!! Reply
  • AppleCrappleHater2 - Wednesday, September 17, 2014 - link

    Worship the holy apple.

    The apple way, selling over expensive crap to stupid consumers that like to
    get robbed.

    This has been a disastrous launch in every respect. The iwatch is such an
    ugly piece of crap, it is truly unbelievable how a company, formerly known for
    its remarkable design, dares to put out such a crap ton of shit. Some
    characteristics are glaringly obvious and inherent to it: over expensive,
    hardly innovative, limited functionality and usability (need of an iPhone to
    make it work), looks exactly like a toy watch and so on.

    There are of course way better smart watches out there, especially form the
    likes of Samsung, Sony, Motorola, Asus, LG, simply put, there is no need for
    another piece of over expensive junk.

    The iPhone 6 is technologically stuck in pre-2011 times, a base model witch
    a capacity of 16GB without the possibility to use SD cards isn't even funny
    anymore. The screen resolution is horrendous, it isn't water proof, shock and
    dust resistant, it offers nothing innovative, just some incremental
    updates over its predecessor, both lacking severely behind their competitors at
    their respective launch dates.

    Now the Iphone 6 Plus offers a „Retina HD“ screen, full 1920x1080p, oh wow,
    where have you been for the past 4 years apple, talk about trailing behind.
    That’s pathetic. The interesting thing about that is the fact that apple
    always manages to sell backwards oriented, outdated crap to its user base, all
    while pretending to be an innovative technology leader. The similarities
    regarding any form of sectarian cult are striking.

    You gotta love how Apple always comes up with new marketing bullshit terms,
    aka "Retina HD", with the intention to manipulate its users while preventing easy
    comparisons with its competitors by withholding the actual specs. Apparently it’s
    not enough to have an 1080p screen, you have to call it "Retina HD" to make those
    suckers buy it, otherwise someone could look at the 4K Amoled and Oled screens
    form LG and Samsung devices and get outright disappointed. Same goes for
    everything else. Every outdated „feature“ needs to get its own marketing label
    to persuade buyers with crappy „experience“ and „usability“ ads, while covering
    the truth with marketing gibberish, knowing full well that only a fraction of
    aforementioned buyers cares to look at the facts and dares to compare them.

    Car engines come to mind. For comparisons shake let’s look at a 1.0 liter, turbo
    charged petrol engine and a V8 compressor. What’s better should be obvious, but
    by calling the former an „ecobooster“, thus giving it a special marketing label,
    this joke becomes a „feature“, something positive that can be added tot the list
    of features of a car.

    By doing so a negative aspect is transformed into a positive one, the
    reality is distorted, non tech savvy buyers are manipulated and comparisons are
    made more difficult (another layer of marketing bullshit to overcome), well done
    marketing department. You see , if something is seriously lacking (of course for
    profit, what else), don’t bother explaining, just give it a nice marketing term, distort
    reality, make it a feature and call it a day. Fuck that!!

    The Apple Iphone 1 and Ipad 1 might have been innovative at their time,
    but since then, the bitten apple has been continuously rotting from the inside
    outwards, always swarmed by millions of Iworms which regale themselves with its
    rotten flesh, not forgetting all other Americans who support apple by means of
    their tax dollars to finance its bought US Treasury/Government bond interest rates.

    Last but not least, every Apple product includes a direct hotlink to the nsa,
    free of charge, something that might make it a good value, after all.

    Ceterum censeo Applem esse delendam.
    Reply
  • Achtung_BG - Friday, September 19, 2014 - link

    Apple A8 CPU test:
    SunSpider ~ 350ms
    Geekbench ST~1600, MT~2900
    Linpack MT~ 1380MFLOPS
    GPU test GFXbench 3.0 off-screen ~ 18 Fps
    Reply
  • alwasih - Wednesday, September 24, 2014 - link

    I've always been curious, why is there a very large gap between the Apple A7 and Snapdragon 800/801 when it comes to single core geekbench scores? Is the Apple A7 really that much more powerful than the Snapdragon 801? Or is it because of the new ARM v8 instruction set used by the A7? The A7 actually attains these high scores while operating at much lower frequencies too. Its astonishing. Reply

Log in

Don't have an account? Sign up now