iPhone 15: users of Pro and Pro Max models complain of overheating issues

The iPhone 15 Pro series launch, featuring the highly anticipated A17 Pro chip and titanium frame, has encountered some challenges for Apple. The new chip was expected to enable the introduction of cutting-edge AAA gaming titles, typically reserved for gaming consoles and PCs, to the iPhone platform for the first time. The use of titanium was intended to enhance strength, reduce weight, and provide a more premium aesthetic. However, concerns have arisen regarding the potential issues associated with these exclusive features present in the iPhone 15 Pro.


Shortly after customers began receiving their new iPhone 15 Pro and Pro Max models, reports emerged on social media platforms highlighting instances of overheating. This overheating could occur during phone calls, phone charging, gaming, and other routine activities that would not normally lead to the iPhone becoming uncomfortably hot to the touch. It is worth noting, however, that not all users have encountered such problems with their new iPhones. In our possession, an iPhone 15 Pro Max unit has not exhibited any of the overheating issues reported by some users.


According to Apple analyst Ming-Chi Kuo, the heating issues experienced by iPhone 15 Pro users are more likely attributed to the absence of an optimized cooling system, rather than being directly linked to the A17 Pro chip or the new TSMC 3 nm (N3B - "Basic") fabrication process. Kuo identifies the "reduced heat dissipation area" and the "use of a titanium frame" as the reasons behind the problem. Titanium, unlike the previous steel frame, does not efficiently dissipate heat. Consequently, more of the heat generated by the phone's internals needs to be dissipated through the rear glass panel.


Ironically, Kuo previously mentioned in 2021 that Apple was actively testing vapor chamber cooling for a forthcoming iPhone model. However, this technology has not been implemented in any iPhone as of yet. Vapor chamber cooling is commonly employed in top-tier Android devices to address heat dissipation concerns in high-performance chips. If Apple had integrated a vapor chamber in addition to the graphite used for cooling in the iPhone 15 Pro, it would have partially or completely mitigated the heat problems experienced by some users. Considering the iPhone 14 Pro's prior issues with performance throttling under sustained loads due to Apple's minimalistic cooling approach, it is somewhat surprising that Apple did not opt for a more robust solution this time, especially with the purportedly more efficient TSMC 3 nm node, which should result in cooler operation.


Despite Kuo's assertion that the A17 Pro chip and TSMC's new 3 nm process are not the main culprits, there remain questions about their potential roles, particularly considering the significant number of iPhone 15 Pro users who have not encountered any issues. It is noteworthy that all models are equipped with the same graphite-based thermal solution. Apple notably secured most of TSMC's production capacity for its new N3B node, as die-shrinks generally offer notable gains in performance and/or efficiency. However, TSMC reportedly faced several challenges in fabricating chips on this node, resulting in a relatively low yield of functional chips (only 55%). This could lead to increased variability in chip performance, commonly referred to as the "silicon lottery," which might explain why only some users are experiencing problems.


Another aspect of TSMC's 3 nm process that raises questions is its continued use of FinFET technology. Although FinFET has proven effective at the 5 nm and 4 nm scales for TSMC, it encounters difficulties when further scaled down due to issues related to controlling current leakage, resulting in overheating. TSMC has implemented certain technical measures to mitigate these issues and related challenges, although it appears that they may not have completely eliminated them. Samsung Foundry, another original equipment manufacturer (OEM), has initiated the production of 3 nm chips but utilizes different technology. Despite encountering various issues with its node technology in recent years, Samsung has adopted the Gate All Around (GAA) approach, utilizing its own implementation known as MBCFET (Multi-Bridge-Channel FET). GAA is widely regarded as superior technology at these scales, offering notably enhanced power management and other benefits.


TSMC stated that its 3 nm node would deliver 15% better performance and consume up to 35% less power compared to its N5 node. However, during the iPhone 15 Pro launch, Apple claimed that the A17 Pro's CPU performance would only be around 10% faster and would provide similar battery life to the previous iPhone 14 Pro series, despite slightly higher battery capacities in the new models. This suggests that TSMC's 3 nm node did not meet the company's promises. Interestingly, although the A17 Pro chip has approximately 3 billion more transistors than the A16 chip, Apple had to increase the CPU clock on the A17 Pro to achieve performance gains, which could potentially lead to overheating issues. This also helps explain the lack of improvement in battery life despite the touted advantages of the new 3 nm process.


Another crucial component of Apple's A17 Pro chip that deserves scrutiny is its all-new GPU design. Apple claims it to be the most significant GPU architecture overhaul since they began designing Apple silicon. It incorporates hardware accelerated ray tracing and mesh shading support. To showcase its power, Apple partnered with leading PC game makers to bring popular AAA games like Death Stranding, Assassin's Creed Mirage, Resident Evil Village, and Resident Evil 4 to the platform. Notably, Resident Evil Village is exclusively available on the new iPhone 15 Pro models and iPads with an M1 chip or newer.


However, there are doubts surrounding the new GPU. According to The Information, Apple initially intended to introduce this GPU architecture in the A16 Bionic chip last year but decided against it due to prototype GPUs causing device overheating and excessive power consumption. The incident was considered a significant mistake by Apple's silicon team, which had also experienced the departure of several top chip engineers to other companies or startups around the same time. Undoubtedly, Apple continued refining the design in the months that followed before eventually incorporating the new GPU architecture in the A17 Pro. The engineers likely anticipated that the die-shrink to a seemingly more efficient node would address any remaining concerns regarding overheating and power consumption, provided it performed as expected.


We conducted tests on the iPhone 15 Pro Max using the industry-standard 3D Mark Wild Extreme Stress Test, a graphically demanding loop that runs for 20 minutes. This test measures the sustained performance of a chip's GPU, which is crucial for determining how long a device can maintain a certain level of performance. This is particularly relevant for users engaging in graphically demanding activities such as gaming, a feature that Apple has emphasized with this year's Pro models. As indicated in the "Performance range" graph below, the iPhone 15 Pro Max outperformed the iPhone 13 Pro Max in overall performance.


The iPhone 13 Pro features the A15 Bionic chip fabricated on TSMC's well-regarded 5 nm (N5P) node. Despite lower frame rates, which can be expected given the older GPU design, the sustained performance profile of the A15 Bionic is very similar to that of the A17 Pro, with both chips starting to experience performance issues around the 130-second mark. However, it is intriguing that the sustained performance characteristics of the older N5P process are nearly identical to those of the newer N3B process. Additionally, the battery life of the iPhone 15 Pro dropped by 10% during the test, comparable to the decline observed in the iPhone 13 Pro, despite the latter having an older battery.


These findings indicate a lack of apparent efficiency gains across both nodes and GPU architectures, contrary to TSMC's claim of potential 35% efficiency improvements over the N5P node. It is also worth noting that the A17 Pro exhibited less stability during the test, with a 67% stability rating compared to the A15 Bionic's 73.6%. These results do not align with expectations for a chip utilizing newer architecture on a cutting-edge and more efficient node. Instead, they reflect the impact of the "silicon lottery" mentioned earlier, which becomes particularly pronounced when yields are relatively low.


In terms of heat, both the iPhone 15 Pro and the iPhone 13 Pro exhibited warm surface temperatures upon touch. However, our iPhone 15 Pro Max showed no unusual signs, unlike certain iPhone 15 Pro Max models that experienced similar benchmark performance. Notably, the titanium variant of the iPhone 15 Pro Max felt cooler to the touch in comparison to the steel-framed iPhone 13 Pro Max. This discrepancy can be attributed to the varying thermal conductive properties of the two materials. Consequently, it can be inferred that the thermal dissipation requirements are higher for the iPhone 15 Pro design, which utilizes glass. Nevertheless, it is worth mentioning that not all iPhone 15 Pro models suffer from overheating issues. While a more robust cooling solution might have been desirable, this suggests that the problem is likely attributable to factors other than the thermal design.


Several potential factors could contribute to the overheating experienced by certain iPhone 15 Pro models. For instance, third-party applications that have not been optimized for iOS 17 could be a source of concern. It is possible that these apps are only installed on some devices and not others. Alternatively, the problem might stem from system software and firmware issues specific to certain regional iOS 17 builds. If a problematic rogue app is identified, a potential solution could involve examining the battery settings for any app consuming excessive power and CPU cycles and subsequently removing it from the device. In the case of an issue related to the operating system, Apple is expected to release a patch in the near future to address the problem. Conversely, if the issue is hardware-related, it would necessitate Apple's acknowledgment and subsequent initiation of a special service program to rectify the matter.


For individuals considering the purchase of an iPhone 15 Pro but are concerned about potential heat-related issues, it is advisable to acquire the device from an official Apple Store or another retailer offering a fee-free return policy. This ensures a hassle-free return option if necessary. However, for those who already possess an affected iPhone 15 Pro but are unable to return it, patience becomes crucial as they await potential solutions or updates.