With auspicious consistency, everyone who was able to get their hands on the iPad couldn’t stop raving about how fast it was. Powering the iPad is Apple’s homegrown A4 chip, but truth be told, we really don’t know much about it. Until now.
Jon Stokes writingfor Ars Technica:
As I watched the videos and read the reports of the iPad in action at the launch event, I was thoroughly convinced that the device was built on the out-of-order Cortex A9, possibly even a dual-core version. But it turns out that the the A4 is a 1GHz custom SoC with a single Cortex A8 core and a PowerVR SGX GPU. The fact that A4 uses a single A8 core hasn’t been made public, but I’ve heard from multiple sources who are certain for different reasons that this is indeed the case. (I wish I could be more specific, but I can’t.)
And as for PA Semi’s involvement in the development of the A4, or perhaps lack thereof:
So if Apple just licensed the A8 and didn’t design a custom CPU core, then what was the point of the P.A. Semi acquisition? The answer to this question is still unclear.
Apple bought P.A. Semi in late April 2008. A little over a year isn’t near enough time to do a new core design around the ARMv7 architecture. Something like Qualcomm’s Scorpion core, which is a custom implementation of ARM v7 that’s comparable to the A8, but with a wider SIMD engine and a deeper pipeline, was a multiyear project. I could easily imagine that Apple is working on something comparable to Scorpion, but this wouldn’t be ready for a while.
If they were involved at all in the A4 design, and it’s still not 100 percent clear that they were, it’s likely that the P.A. Semi team made its biggest contribution to the A4 in the area of dynamic power optimization.