Late last month, Chipworks confirmed that Apple was using two different sources for the A9 chip in the iPhone 6S and 6S Plus: Samsung and TSMC. The chips differ slightly in size, but appear to have largely identical performance.

In the last 48 hours, though, data from users who have compared Samsung phones to TSMC phones have found that the TSMC phones have better battery life. Apple has just issued an official statement on the matter, saying that the battery life tests being used to demonstrate these differences (primarily the test that comes with Primate Labs' Geekbench tool) paint an "unrealistic" picture of real-world battery life. The full statement:

"With the Apple-designed A9 chip in your iPhone 6s or iPhone 6s Plus, you are getting the most advanced smartphone chip in the world. Every chip we ship meets Apple's highest standards for providing incredible performance and deliver great battery life, regardless of iPhone 6s capacity, color, or model. Certain manufactured lab tests which run the processors with a continuous heavy workload until the battery depletes are not representative of real-world usage, since they spend an unrealistic amount of time at the highest CPU performance state. It's a misleading way to measure real-world battery life. Our testing and customer data show the actual battery life of the iPhone 6s and iPhone 6s Plus, even taking into account variable component differences, vary within just 2-3% of each other."

Other tests performed by 6S users came to similar conclusions—the difference was less pronounced when using tests that weren't constantly stressing the CPU. Even so, phones with the Samsung chip do seem to fare slightly worse than phones with the TSMC-produced model.

Apple sources multiple iPhone components from multiple companies, not just chips, which makes it difficult to control for variables in these tests. We've got one iPhone 6S with a Samsung chip and one with a TSMC chip in our hands and are running our own tests to control for variables like cellular connectivity and screen brightness. We'll report back with our results as soon as we can, likely within the next 24 hours.