The iPhone 5 is finally out, but its A6 processor is still somewhat of a mystery. Although the tame Apple press speculated that the A6 is the world’s first SoC based on ARM’s new A15 architecture, Anandtech has a different and perhaps even more surprising theory.

The A6 is not an A15 chip, but it’s not an A9 chip either. Apparently it’s a custom Apple design, based on the ARMv7 instruction set. Anand came to the conclusion after comparing extensions supported the new chip. Originally he thought Apple tapped the new A15 architecture, but it turns out that Apple took the road less travelled.

But why would Apple even bother designing a new chip? Well, for starters it can afford to, literally. With billions in the bank the development of a mobile processor is not an issue. Designing a chip from the ground up to suit the needs of the iPhone delivers an excellent balance of performance and power consumption, and the latter is very important for the featherweight iPhone 5.

Of course, Apple is not designing an entirely new chip solely for the iPhone 5 and we probably won’t wait long to see the new architecture trickle down into other Apple products. The upcoming iPad mini is the obvious candidate. Like the iPhone 5, it is rumoured to be much thinner and lighter than 9.7-inch iPads and it is also said to feature a similar resolution screen, with only about 10 percent more pixels (1024x768 vs. 1132x640). We can’t be sure that the A6 will end up in the iPad mini, but at this point it seems very likely indeed.

So, although the iPhone 5 launch wasn’t very spectacular and did not deliver any world-beating innovations, the biggest innovation could be under the bonnet, in the form of Apple’s first in-house designed mobile chip.

You can check out the geeky details here.