Apple A4 CPU Dissection: iPad is Just a Big iTouch

When Steve Jobs took to the stage earlier this year to unveil the iPad, he also announced a custom processor he called the A4. While the company has been rather mum on what's inside the package, early reports figured the A4 to be ARM-based, just like the iPhone and iPod Touch models. And they were right.

Teardown specialist firm iFixit sent the A4 chip to Canadian-based Chipworks, a semiconductor reverse engineering firm, for an x-ray and dissection to find out what Apple's chip is made up of.

These are the conclusions that iFixit it came to:

· There's not much revolutionary here. In fact, the A4 is quite similar to the Samsung processor Apple uses in the iPhone [3GS].· It's clear from both hardware and software that this is a single core processor, so it must be the ARM Cortex A8, and NOT the rumored multicore A9.· It's quite challenging to identify block-level logic inside a processor, so to identify the GPU we're falling back to software: early benchmarks are showing similar 3D performance to the iPhone [3GS], so we're guessing that the iPad uses the same PowerVR SGX 535 GPU.· The iPad has 256 MB RAM, same as the iPhone [3GS].· The A4 sips power. In fact, power consumption is probably the reason Apple hasn't stepped up performance much from the iPhone [3GS]. In order to get 10 hours of battery life, the entire iPad (including display) has to pull less than 2.5 Watts on average.

It should be noted that, while both the CPU and GPU appear to be upclocked versions of the same things powering the iPhone 3GS, it's still impossible to tell at this stage. Furthermore, there is a single core version of the ARM Cortex A9, so Apple could be using a newer CPU than the A8 in the latest iPhone and iPod Touch.

Nevertheless, we agree with iFixit that, on a hardware level, "there's not much revolutionary here." Apple has essentially built a triple-layer, package-on-package custom chip using off-the-shelf components. Like the company does for the rest of its computing product, it takes something that's readily available in the technology marketplace and layers it with custom software to provide a markedly different experience.