The iPhone 6S Plus packs a powerful punch besides its 5.5-inch display. The device runs on an Apple A9 system-on-a-chip (SoC) just like its smaller sibling, the 4.7-inch iPhone 6S. But ChipWorks has revealed an interesting tidbit: Not all A9 chips are the same.

Instead, two versions exist: one from Samsung (which measures 96mm squared) and one from TSMC (which measures 104.5mm squared). While a similar idea was rumored with the A8 chip, this news is proof. An iFixIt teardown found the TSMC chip (APL1022) in the iPhone 6S Plus, while the smaller Samsung chip (APL0898) was found in the iPhone 6S.

At this point, it is unclear why exactly Apple has chosen to go down the path of contracting two companies to provide the chips. Geekbench scores show the two devices running at near-identical speeds, meaning that if a different company is supplying a different chip for each device, it isn't having a noticeable impact on performance. ChipWorks suggests that for Apple to go through the effort of dual-sourcing a crucial custom chip in this fashion, there may have been some sourcing issues.

It may have simply been to ensure that Cupertino had enough supply to meet demand. Over the launch weekend, the two devices sold 13 million units total, beating the previous iPhone generation of 10 million units in last year's launch weekend. That sits at the high end of Wall Street estimates, where analysts expected Apple to sell between 10 million and 13 million units.