iPad 4’s A6X Chip: Here’s What We Know So Far

ipad-4-retina-displayApple surprised a lot of us during its Special Event yesterday, when it announced a whole new fourth generation iPad as opposed to the tweaked third generation iPad we all were expecting.

While the fourth generation iPad retains the same size, weight and design as its predecessor, it comes with a number of tweaks and changes, the most notable of which is of course Apple’s all new A6X chip.

A lot of criticism of the 3rd gen iPad largely revolved around its under powered processor, which had to handle the mighty task of pushing around 4 times as many pixels as its predecessor, the iPad 2. While the GPU in the A5X was upgraded to handle the 3 million pixels, the CPU remained the same as the iPad 2, which meant that a lot of graphical tasks that took place on the CPU were much slower than the iPad 2. Apple’s unexpected 4th gen iPad update addressed this issue, along with many others that plagued the 3rd gen iPad.

Apple claims that the A6X chip is twice as fast as the A5X found in the 3rd gen iPad, for both CPU and GPU based tasks. The A6X also has an improved image signal processor, the same as the iPhone 5, which makes a lot of image processing related tasks like video stabilisation, face detection and noise reduction much faster and better.

But, as Apple tradition goes, the company didn’t reveal any specifics about the new chip apart from specifying that the CPU is dual core and the GPU is quad core. Of course since the chip is an extension of the A6 chip found in the iPhone 5, we know that it has custom ARM cores designed by Apple based on the armv7s architecture. Extending the similarities between the two chips, we can also safely say that the A6X, just like the A6 chip, is manufactured using the power efficient 32nm process, explaining why the 4th gen iPad retains the same 10 hour battery life as the 3rd gen iPad on the same 42.5WHr battery.

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Ars Technica took a much deeper look at the A6X chip, taking clues from what Apple said about the 2x boost in performance during the keynote, and making educated guesses about the internals of the chip:

Looking at CPU power for the moment, we already know that Apple designed a custom ARM-based core for the A6. Running at 1.2GHz in the iPhone 5, two A6 cores run twice as fast as two 800MHz A5 cores in an iPhone 4S.

However, the A5X in the third-gen iPad was clocked at 1GHz. That means Apple is clocking the A6X higher yet. Given that architectural improvements account for some of the speed increase, Apple only had to clock the iPhone 5 at 150 percent to achieve double the compute performance of the iPhone 4S. With this in mind, we believe Apple is clocking the A6X’s CPU cores at 1.5GHz.

Apple also boasts of a 2x boost in GPU bound tasks, meaning that the graphical processor has been updated as well. Since the number of cores remain the same in both, the 3rd gen iPad and the 4th gen, the only way Apple could achieve a performance boost is by using a new generation PowerVR core or by increasing the clock speed:

Apple could be using a newer-generation PowerVR core, but that appears to be very unlikely. Only one announced processor is known to use a PowerVR Series6 design, and it won’t even begin sampling until 2013. Given that Apple just released the A6 a month ago, we’re confident Apple is still using the same SGX543 core.

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Apple says that the A6X has “quad-core graphics“—the same as the A5X—so Apple clearly boosted the clock speed. Since the GPUs in the A5X were clocked at 250MHz, we believe that Apple has clocked the SGX543 cores at 500MHz.

Additionally, Marco Arment speculates that the excessive heating of the third gen iPad was largely due to the A5X chip, and that the inclusion of a new 32-nm process manufactured A6X chip might solve the issue.

With all this insight into the A6X chip, the 3rd gen iPad, in hindsight, seems to be an awkward stop gap put to ensure that Apple keeps up with the competition in terms of hardware and not exceed the yearly upgrade period. It, however, had no issues releasing another update to the device within a six month period.