Apple's A5, the system on chip that powers the iPad 2 and possibly the iPhone 5, contains a large amount of extra circuitry the purpose of which has yet to be determined.
According to Linley Gwennap (opens in new tab), the senior editor of Microprocessor Report, that surface area, around 33 square millimeters, is larger than the GPU on the A5 which stands at 31 square millimeters and is larger than the surface area of the Nvidia Tegra 2, the SoC that powers rivals like the Motorola Atrix and the LG Optimus 2X.
Because Apple designs its own chip and takes it directly to the fabs, it doesn't have to go through a third party like Nvidia or Freescale and pay a hefty markup in the process.
This means that it can afford to design bigger & more complex chips for the same outlay as its competitors. Some have been saying that the mystery surface area is dedicated to hardware acceleration for graphics functions although it is unlikely Apple will ever comment on it.
Gwennap posits that Apple may be forced to design more than one system on chip to cover its different products, possibly playing around with clock speeds as well as core counts.
Also its gargantuan appetite for anything silicon may push it to collaborate with Intel, rather than Samsung Semiconductors, to produce the A5 and possibly the A6.