Each analysis of Apple's SoC can always make people feel complicated. On the one hand, Apple's SoC always has the best performance, but Apple keeps its own SoC specifications secret every time. It's easy to see the performance improvement, but it's not so simple to figure out how to improve it.
In brief, it has been confirmed that the CPU part of the A8X uses three "enhanced" Cyclone cores, and the 2MB L2 cache has been confirmed. As for the GPU, after combining the performance improvement claimed by Apple and the actual score, we initially thought that the GPU Apple used for the A8X was the PowerVR GX6650 of Imagination, and also the strongest GPU currently shipped by Imagination.
However, with later in-depth exploration, we found that the GPU performance of the A8X is actually stronger than that of the GX6650. First and foremost, Imagination recently released the PowerVR 7-series GPU. Although it is far from the official landing of the 7-series, according to the information given by Imagination, the 7-series supports up to 16 cores, twice as many as the 6-series GPU. Imagination has never released the 6-series GPU with 8 cores, which led us to initially mistake the GPU of the A8X as GX6650.
Secondly, from the test results of GFXBench 3.0, The filling rate of the A8X is twice that of the A8 on the iPhone 6. You should know that this performance is related to the GPU frequency and bandwidth. The filling rate alone cannot determine how many core GPUs are used by the A8X. However, considering that the probability of high frequency GX6650 is too small, we think that the A8X should have made an article on the number of GPU cores.
Today, we received a photo that confirmed our guess. According to this unclear photo, the GPU of the A8X is composed of eight core PowerVR 6 series. The eight cores are clearly visible in this photo. The overall structure is somewhat similar to the GX6450. To put it simply, it is like superposition of two GX6450.
Since it is already an 8-core GPU, the A8X GPU is obviously not the GX6650, but something more powerful than the 6650. Imagination has not released a specific 8-core 6-series GPU. But it is not impossible to design one of your own for Apple, which is crazy.
So the problem arises. Imagination did not specifically give a formal name to the six series of 8 cores, and Apple naturally does not have any name. So we give full play to the wisdom of working people, and we decided to call the GPU of the A8X GXA6850.
In terms of specifications, the GXA6850 is basically two GX6450s. In terms of unit design, Apple has made some necessary connections to the eight GPU cores and optimized the power supply design based on the new GPU. In addition, there is no novelty. The GXA6850 can be characterized as a semi customized GPU rather than a fully customized GPU.
The chip area of A8X is about 12.5mm x 10.0mm, that is, 125mm2, which is a little larger than that of A6X. The total number of transistors is about 300 million. Among them, the area of GXA6850 is about 30%, that is, about 38mm2. It is the 20 nanometer process that can make it so small.
As for why Apple chose the 8-core solution instead of the 6-core solution, the most likely reason should be the performance. When comparing the On Screen score of the Air 2 with that of the iPhone 6 Plus, we found that although the total number of screen pixels of the Air 2 is almost twice that of the 6 Plus, the performance of the Air 2 still has obvious advantages, The performance of the Air 2 on a single pixel is 30% better than that of the 6 Plus. Apple clearly wants to build the Air 2 into a game console.
As for the CPU part of the A8X, there is no surprise, that is, the 3-core design, and this 3-core design is not achieved by shielding one core from four cores. It is true that the number of odd cores is rare, but Apple has nothing to complain about if it wants to do so, after all, the performance.
To sum up, it's very simple. Apple's A8X shocked us again with its extremely cool performance. The performance of both the A8X and GXA6850 is much stronger than we expected. Apple has always had a high eye and a high hand.
In terms of performance level, with 256 ALUs, A8X's powerful GPU has stood at nearly the same level as low-end desktop tablet GPU. At present, only Nvidia's K1 can compete with A8X's mobile SoC. As for other mobile SoCs, stand aside first.
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