The iPhone 15 Pro has an overheating problem that could spell trouble for Apple’s custom line of semiconductors.

The latest iPhone Pro is powered by the all-new A17 Pro chip, the first 3nm chip used in a mobile device. Apple’s chips are based on Arm designs which are renowned for offering a strong blend of performance and energy efficiency.

Unfortunately, a myriad of reports have started surfacing indicating that the iPhone 15 Pro and Pro Max are running significantly hotter than their predecessors.

Android Authority’s Robert Triggs did a deep dive, thoroughly testing the new models to see how they compare to other flagship devices. The results are not good news for Apple.

While the iPhone stayed within a degree or two of other flagship devices under most tests, when the device was used for more intense operations, the heat quickly rose far beyond its competitors.

However, once we move into more demanding waters that engage more SoC components, it’s clear that the A17 Pro chip is an issue. Turn on the six-core GPU and temperatures spike quickly. Our iPhone 15 Pro passes the 40°C mark within five minutes of running the 3DMark Wild Life stress test. Wait until the end of the 20-minute run, and the phone’s 47°C peak verges on too hot to hold. The Galaxy S23 Ultra doesn’t do great here either, but the iPhone 15 Pro is 5.7% hotter, and any handheld device approaching 50°C with any workload is worrisome.

Our 4K/60 video recording test showcases the most significant discrepancy. After just five minutes, the iPhone 15 Pro is about 7°C hotter than the S23 Ultra and 4°C hotter than the Pixel 7 Pro, a phone already widely regarded as too warm. Worse, the iPhone 15 Pro far exceeds an acceptable level of comfort in the hand after extending the test to 10 minutes.

While a single model overheating is concerning enough, it’s especially so when considering the iPhone Pro uses the latest and greatest Apple-designed, TSMC-manufactured silicon.

The results raise questions about whether Arm-based semiconductor design still has room to increase performance without a significant increase in heat, or whether it has hit a thermal limit.