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I spent two days with the iPhone Duo in our test labs to run our long list of benchmarks, but before handing it over to my colleague for a full review, I wanted to know: How does the iPhone Duo handle heavy loads like gaming compared to the Z Fold 8 — and what does that mean for how hot the phones get? Is there thermal throttling on either phone?
To answer my question, I ran the 3DMark Wild Life Extreme Stress Test in a 20 minute loop on both phones. These benchmarks simulate a long gaming session, and the results were very different on every phone.
Apple’s phone came out hotter than Samsung’s at the end of my tests, but it managed to deliver better performance. But does that actually make it a better foldable for gaming and sustained workloads? There is only one way to find out. Here is what I found out.
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iPhone Duo vs Galaxy Z Fold 8: The thermal camera analysis
For my test, I set up the iPhone Duo as well as the Z Fold 8 in our Tom’s Guide Studio under our normal studio lighting. Both phones were unfolded and set to their default refresh rates, cooled of course before placing them on a plastic mat on our studio surface.
I then started the 3DMark Wild Life Extreme benchmark on the interior displays and turned their screens down. Using a FLIR One thermal camera connected to a Pixel phone, it was used to record the rear of the phones during the 20 minute loop.
The results for this test may vary based on the setup, but under the thermal imaging camera during the sustained stress test, both devices showed some truly unique heat signatures and thermal dissipation patterns.
On the right side, the Galaxy Z Fold 8 has a bright, intense heat point concentrated near the upper section where the CPU is known. Over time, this hot spot expands outwards over the rear surface, and to the right side of the screen, the surrounding area turns noticeably red under the thermal lens as the heat has saturated the chassis. The primary place where the heat signature started was still bright and hot though.
Meanwhile, the iPhone Duo produced a much more balanced, uniform heatmap. The heat has been distributed over a wider surface rather than forming a single localized hotspot, keeping surface temperatures and heat more even across the frame and display rather than at a peak.
After checking the temperature on both phones in the same place, the iPhone was hotter at 103 degrees. The Z Fold 8, meanwhile, is slightly cooler to the touch at around 96 degrees.
A cooler phone might sound better, but my benchmark results revealed a trade-off! The Galaxy Z Fold 8 retained less of its graphics performance during sustained tests, despite its lower outside temperatures.
iPhone Duo vs Galaxy Z Fold 8: Stress Test Results
When I recorded the results of the 3DMark Wild Life Extreme Stress Test, the iPhone Duo achieved a higher stability score of 67.9%, which shows better sustained performance over the 20-loop stress test compared to the Galaxy Z Fold 8, which scored 51.4%.
The best loop score of the test hit 7,639 on the iPhone Duo, compared to 7,047 on the Galaxy Z Fold 8. This is when the phones are at their best performance. Meanwhile, after thermal limitations come into play, the lowest score drops to 5,184 for the iPhone Duo and 3,626 for the Galaxy Z Fold 8.
The numbers may sound confusing, but a higher stability score is better, and the loop score shows how the phone’s performance has changed over time. In the end, the iPhone Duo wins in all three tests.
iPhone Duo vs Galaxy Z Fold 8: Engineering difference
Why did things end like this? The Z Fold 8 relies on relatively basic thermal management materials rather than the vapor chamber setup seen on the iPhone Duo. Therefore, the heat generated by the processor seems to be trapped near the top of the phone on the Z Fold 8.
Despite remaining cooler outside, the Galaxy Z Fold 8 lost a greater proportion of its performance during the stress test. This shows that the iPhone Duo is better at maintaining performance, although this is a synthetic benchmark, so the results may vary based on what task the phones are pushing.
Nevertheless, the iPhone Duo draws heat directly from the processor and pushes it outwards over the body and the display. Therefore, the device feels significantly warmer on its outer surface. However, by successfully dumping this heat from the core, it keeps the internal processor dramatically cooler.
This also explains the internal sensor data captured by 3DMark during the stress test. The Samsung phone’s core rises from 95°F to a hot 113°F internally.
iPhone Duo vs Galaxy Z Fold 8: Bottom line
The lesson is simple: Think of the iPhone Duo like a NASCAR stock car with an advanced cooling system. When the engine is pushed hard, the cooling system moves the heat away from the processor and distributes it over a larger area of the phone’s body. That can make the exterior hotter to the touch, but it also helps the processor maintain high performance for longer without thermal throttling.
The Galaxy Z Fold 8 is different. Under sustained, demanding workloads, their cooling limitations can decrease performance as the processor reduces power to control temperatures. The phone may feel cooler in some situations, but a cooler exterior alone doesn’t tell you how effectively heat is managed internally.
What does that mean for you? If you are a mobile gamer, sustained performance is more important. During 20-30 minutes of demanding gameplay, a phone with better thermal management can maintain higher frame rates and deliver more consistent gameplay. On the other side of things, a phone that gets hot around the CPU will run more aggressively lower frame rates or sometimes stutter.
At least from my tests, there is no doubt about it. The iPhone Duo wins. Its cooling design gives it a promising advantage for gaming and sustained performance, compared to how it performs on the Galaxy Z Fold 8 in our same test conditions.
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