CPUs


Analyzing Apple’s A8 SoC: PowerVR GX6650 & More

Analyzing Apple’s A8 SoC: PowerVR GX6650 & More

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

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.

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.

IDF 2014: Intel Edison Development Platform Now Shipping

IDF 2014: Intel Edison Development Platform Now Shipping

As part of today’s IDF 2014 keynote, Intel has announced that their Edison development platform is now shipping.

First announced back at CES, Edison is a development platform for Intel’s burgeoning Internet of Things development ini…

IDF 2014: Intel Edison Development Platform Now Shipping

IDF 2014: Intel Edison Development Platform Now Shipping

As part of today’s IDF 2014 keynote, Intel has announced that their Edison development platform is now shipping.

First announced back at CES, Edison is a development platform for Intel’s burgeoning Internet of Things development ini…

IDF 2014: Intel Demonstrates Skylake, Due H2’2015

IDF 2014: Intel Demonstrates Skylake, Due H2’2015

Taking place this week alongside the consumer electronics clamor is the annual Intel Developer Forum (IDF) at the Moscone Center in San Francisco. Though it has and continues to be first and foremost a developers conference, IDF also offers Intel a chance to unveil new products, and in more recent editions discuss and promote their plans for further breaking into the mobile market.

Diving right into the subject of Intel’s Core microarchitecture, with the Broadwell based Core M already in the process of launching, Intel is giving developers and the public a look at what comes after Broadwell. Already on Intel’s roadmaps for some time, Intel took to the stage at IDF14 to formally announce their next-generation Skylake architecture and to demonstrate its status.

Intel’s Tick-Tock Cadence
Microarchitecture Process Node Tick or Tock Release Year
Conroe/Merom 65nm Tock 2006
Penryn 45nm Tick 2007
Nehalem 45nm Tock 2008
Westmere 32nm Tick 2010
Sandy Bridge 32nm Tock 2011
Ivy Bridge 22nm Tick 2012
Haswell 22nm Tock 2013
Broadwell 14nm Tick 2014
Skylake 14nm Tock 2015

In Intel terminology Skylake is the Tock to Broadwell’s Tick, offering a new microarchitecture atop the 14nm process first introduced with Broadwell. As is the case with every Core update, for Skylake Intel is shooting for significant increases in performance, power efficiency, and battery life. Since Skylake is built on the same 14nm process as Broadwell, Skylake is primarily an exercise in Intel’s architecture development capabilities, with its gains needing to come from optimizations in design rather than significant manufacturing improvements.             

At roughly a year out from launch Intel is not saying anything about the architecture or design at this time, but they are using IDF to showcase that Skylake is up and running. Demonstrating this, Intel showcased a pair of Skylake development systems. The first of which was a traditional open laboratory testbed that was running 3DMark, which was being used to showcase that the GPU and CPU portions of Skylake were running and performing well. The second demonstration was a completed laptop that was playing back 4K video, and is an early version of the hardware Intel will be shipping as the software development vehicle for developers next year.

Alongside their demonstration, Intel also announced a rough timeline for the volume production and availability of Skylake. Volume production will take place in H2’2015, with product availability slated for later in the year. With Broadwell being behind schedule due to a slower than planned bring-up of their 14nm process, there has been some question over what would happen with Skylake and Intel clearly wanted to address this head-on.

Consequently a big part of Intel’s message on Skylake is that the next generation CPU is already up and running and is in a healthy state, apparently unfazed by the earlier 14nm delays that dogged Broadwell. At the same time the H2’2015 launch date for Skylake means that it’s going to be out roughly a year after the first Broadwell parts, which means Intel still intends to adhere to their roughly 1 year product replacement cadence.

Apple Announces A8 SoC

Apple Announces A8 SoC

As expected from this year’s iPhone keynote, Apple has announced a new member of their internally developed family of ARM SoCs.

The latest SoC, dubbed A8, is Apple’s first SoC built on the 20nm process, and among the first SoCs over…