According to AnandTech, Apple’s A6 processor, which powers the iPhone 5, is a custom chip.
In the past, the processor was based on ARM cores. Here’s a portion of the report:
However, just prior to the announcement I received some information pointing to a move away from the ARM Cortex A9 used in the A5. Given Apple’s reliance on fully licensed ARM cores in the past, the expected performance gains and unpublishable information that started all of this I concluded Apple’s A6 SoC likely featured two ARM Cortex A15 cores.It turns out I was wrong. But pleasantly surprised.The A6 is the first Apple SoC to use its own ARMv7 based processor design. The CPU core(s) aren’t based on a vanilla A9 or A15 design from ARM IP, but instead are something of Apple’s own creation.