Confusion reigns over Apple's iPhone 5 processor

Posted by Trent Nouveau

A new report is claiming that Apple's recently unveiled iPhone 5 is actually powered by a custom ARMv7 core, rather than a design based on ARM's Cortex-A15 architecture.



Earlier this week, a number of journalists and analysts speculated that the latest-gen smartphone was equipped with an indigenously designed Apple A6 processor based on ARM's dual-core Cortex-A15 chip architecture.

Confusion reigns over Apple's iPhone 5 processorHowever, Anand Lal Shimpi now says he has evidence  that the A6 is the "first Apple SoC to use its own ARMv7 based processor design" and features cores based on Cupertino's own creation.



"I [originally] concluded Apple's A6 SoC likely featured two ARM Cortex A15 cores. It turns out I was wrong - but pleasantly surprised," Lal Shimpi explained in an extensive analysis posted on AnandTech.  
 
"The A6 is [actually] 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."


According to Lal Shimpi, the iPhone 5 will ship with and only run iOS 6.0, with Apple recently seeding a newer version of its dev tools. Apparently, Xcode 4.5 implements two major changes - it axes support for the ARMv6 ISA (used by the ARM11 core in the iPhone 2G and iPhone 3G), keeps support for ARMv7 (used by modern ARM cores), while adding support for a new architecture target designed to support the new A6 SoC: armv7s.



"For unpublishable reasons, I knew the A6 SoC wasn't based on ARM's Cortex A9, but I immediately assumed that the only other option was the Cortex A15," he said. "[So] I foolishly cast aside the other major possibility: an Apple developed ARMv7 processor core."



Unfortunately, says Lal Shimpi, official details regarding the design of Apple's custom core are virtually non-existent at this point.

"Despite Apple's willingness to spend on die area, I believe an A15/Krait class CPU core is a likely target. Slightly wider front end, more execution resources, more flexible OoO execution engine, deeper buffers, bigger windows, etc.



"Support for VFPv4 guarantees a bigger core size than the Cortex A9, it only makes sense that Apple would push the envelope everywhere else as well. I also have no indication how many cores there are. I am assuming two but Apple was careful not to report core count (as it has in the past)," he added. 



Apple's iPhone 5 is scheduled to begin shipping on September 21. A subsequent teardown of the device - which is likely to be almost immediate - will undoubtedly help clear up some of the above-mentioned chip confusion.