What Is The A9X? Apple’s New CPU King Analyzed

With the launch of the iPad Pro, Apple officially made the jump into high performing tablets. Aimed towards enterprise and professional users, the larger iPad promises to offer unparalleled performance when it comes to running demanding apps. Most of this is the courtesy of the A9X that ticks under the iPad's hood, a processor powerhouse according to benchmark results. The A9X is the successor to the A8X, Apple's popular CPU launched with the iPad Air 2 last year and today we get to find out what its all about.

The Apple A9X Gets Dissected; Larger Core Area Attributed Mostly To GPU

When Apple launched the iPad Air 2 last year, the company was facing quite a lot of heat from its competition. Google's Nexus 9 was right there with Nvidia's Tegra K1 running under the hood and promising desktop class graphics performance on a tablet. To counter this, the company needed a performance powerhouse of its own that could stand its ground and along came the A8X. The tri-core cyclone processor began to show its prowess soon after the iPad Air 2 was launched and was heralded as one of the finest processors around.

But while we might not have seen a successor to the iPad Air 2 this year, the A8X did see an upgrade and Apple chose to rely more on its CPU design teams this time around, choosing to power the much more demanding 12.9 inch iPad Pro with the A9X, a processor that you'll see is quite different from its predecessor. Starting from the number of cores, it had been speculated that the A9X comes with two cores on board, instead of three and Chipworks' dissection confirms this today.

As you can see in the image below, the green box highlights the CPU part of the A9X  and Apple choosing two cores instead of three might have a lot to do with the 14nm FinFET. The 14nm FinFET used on the A9X is a relatively new process and the A9X is a huge chip in terms of die size, so adding another core into the mix would most likely have driven up costs for Apple. Plus, given the corresponding transistor increase with the overall area only ends up increasing the complexity of the chip and looks like Apple decided to play it safe this time around.

Moving ahead from the CPU, Apple has paid a special attention to the A9X's GPU this time around as well, just as it did with the A8X. The A9X comes with six total GPU clusters, each of which are highlighted with blue boxes in the image above. Furthermore, each cluster comes with two clusters of its own, making a total of 12 GPU clusters on the core and a cumulative sum of 384 stream processors, which are very impressive. Given the need of the iPad Pro to run heavy duty applications, such a change isn't surprising however.

Just like last year, this year's GPU on the A9X is also a custom iteration of Imagination Technologies' Series 7XT graphics, since the manufacturer lists products with clusters of 2,4,6,8 and 16 clusters only. Another interesting feature on the A9X is the memory cache. The chip doesn't come with a L3 cache on board, while its smaller cousin does. This is most likely due to the fact that the A9X has a larger overall area when compared to the A9, which leads to twice the memory bandwidth of the A9 and therefore twice the rate of data transfer.

It also measures 147mm^2 in overall surface area, which is huge when compared to the 96 and 104.5 mm^2 of Samsung's and TSMC's A9 offerings respectively. Given this already massive surface area and the fact that further cache memory might have driven up costs without a similar increase in performance. Furthermore, it can also contribute further towards heating issues and given the already demanding processing needs of the iPad Pro, could very well have proven to be counterproductive.

That ends our brief analysis of the Apple A9X. Thoughts? Let us know what you think in the comments section below and stay tuned for the latest.

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