updated 12:15 pm EDT, Thu October 13, 2011
iPhone 4S uses newer dual-mode chip
(Update: RAM confirmation) A still-ongoing teardown of the iPhone 4S has shown that the internal upgrades come from more than just the A5 processor. The now officially dual-mode phone is using a Qualcomm MDM6610, a slight upgrade from the MDM6600 seen in the iPhone 4 just eight months ago. What Qualcomm has done, if anything, with the new model isn't known, but both the old and new chipsets can handle the 14.4Mbps HSPA 3G on carriers like AT&T as well as EVDO Revision A on CDMA networks like Sprint's or Verizon's.
The inside otherwise helps prove that some part leaks ahead of time were accurate. Its battery has the extra 0.5Wh of power seen in one part, and other parts of the mainboard match a handful of descriptions. For existing iPhone owners, the most conspicuous differences are visible on the outside, where the CDMA iPhone's antenna design is mixed with a SIM card slot.
More details are forthcoming, although they note that the rare pentalobular screws have carried over from the mid-cycle change and make it harder to get inside for those that only have regular Philips screwdrivers.
The changes reflect the evolutionary approach to the iPhone 4S but also show that it was refining the whole design, not just key components like the processor or camera, when planning the new model. A sharper break is more likely with the 2012 model, which fits in with an increasingly evident pattern of alternating conservative and radical upgrades to the iPhone.
Update: A look at the A5 chip package shows an "E4E4" marking that refers to having a pair of two-gigabit (256MB) low-power DDR2 chips inside the die, pointing to it keeping the same 512MB as the previous generation.