The iPhone 5 rumor mill is spinning up again after apparently taking a few weeks off due to heat exhaustion. The latest buzz coming out of Taiwan is that the device will feature a quad-core processor based on Samsung's Exynos platform. That would make the Exynos 4412 the most likely candidate for the device, and we've already seen an excellent phone built around that platform -- the Samsung Galaxy S III
(although the US version we've looked at here is dual-core Qualcomm Krait).
The Samsung Exynos 4412 is a great platform -- but not necessarily the best fit for a next-gen iPhone 5
The Galaxy S III's excellent battery life is proof that Samsung has managed to reduce the basic power consumption penalty of a quad-core device to virtually nothing, but the company has a better SoC already scheduled for a 2H release. What we'd really like to see in the next-gen iPhone is Samsung's Exynos 5 5250 platform. This solution (also referred to as Exynos 5 Dual) is a dual-core CPU based on the ARM Cortex-A15 core. It's clocked faster (1.7GHz vs. 1.4GHz), the CPU is more efficient, and the phone supports 800MHz LPDDR3, rather than topping out at 400MHz LPDDR2.
It's certainly possible that Apple has done a great deal of behind-the-scenes work to optimize iOS 6 for a quad-core device, but the plethora of dual and single-core CPUs on the smartphone market means that the app market will only slowly optimize for quad-core. This is one reason why Intel's Medfield is as competitive as it is with mainstream phones, despite being a single-core + Hyper-Threading, and it's something Apple can take advantage of as well. Four quad-core A9's at 1.4GHz isn't bad, but two 1.7GHz A15's would be faster in a number of tests, and might consume less power as well.
DigiTimes suggests that the quad-core competition overall will heat up substantially in the back half of this year, with new phones based on Nvidia's low-cost "Kai" quad-core platform, 28nm chips from Qualcomm, and fresh competition from Chinese handset manufacturers like Huwei, ZTE, and Meizu. Quad-core A15's will provide the highest overall performance in 2012, but such chips are likely too far out to make an appearance in Apple products this year.