iPhone Duo performance and thermals

iPhone Duo runs the same A20 Pro chip as iPhone 18 Pro, and published benchmarks show it matching that phone in short tests. The catch shows up under long, heavy loads, where reviewers reported more heat than on the Pro models and HTX Studio recorded lower sustained gaming frame rates.

This is a roundup of what reviewers and benchmark outlets published. Every benchmark score below belongs to the outlet named next to it.

What Apple says about A20 Pro

Apple's iPhone Duo spec page lists A20 Pro with a 6-core CPU (two super cores and four efficiency cores), a 7-core GPU with Neural Accelerators, a Dual 16-core Neural Engine and hardware-accelerated ray tracing. Both displays support ProMotion with adaptive refresh rates up to 120Hz, per the same page.

In its iPhone Duo announcement, Apple calls A20 Pro the same chip used in iPhone 18 Pro models, built on a 2-nanometer process. Apple says the CPU is up to 20 percent faster than A19 Pro, and claims a GPU up to 40 percent faster without naming the comparison in that release. Apple also cites 50 percent more unified memory bandwidth.

The cooling claim is the one that matters most here. Apple says a new chip package connects A20 Pro directly to a custom vapor chamber, delivering "up to 35 percent better sustained performance than iPhone 17 Pro."

The hinge plays a part too. 9to5Mac, relaying a PCMag interview with Apple engineers, reports that Apple routed a flexible graphite pipe through the hinge to move heat between the two halves.

Short benchmarks: level with iPhone 18 Pro

Quick CPU tests put iPhone Duo in the same place as iPhone 18 Pro. The table below is built from figures published by Tom's Guide and Gizmodo; scores from different outlets aren't directly comparable.

Gizmodo's Raymond Wong averaged three Geekbench 7 runs and reported that iPhone Duo and iPhone 18 Pro scored nearly identically. By our calculation from Gizmodo's scores, the Galaxy Z Fold 8 trailed iPhone Duo by about 22 percent in single-core and about 71 percent on the GPU test, with multi-core close.

Macworld's Jason Cross, in his iPhone Duo review, found 3D graphics benchmarks ran slightly slower than on iPhone 18 Pro, though still ahead of every earlier iPhone and other foldables. He calls iPhone Duo "far and away the fastest folding phone you can buy."

Sustained load: where iPhone Duo gives ground

Longer tests tell a different story. According to Consomac's report on tests by the YouTube channel HTX Studio, iPhone Duo averaged 33.63 fps in a 30-minute Death Stranding session, versus 41.82 fps for iPhone 18 Pro. The same report has iPhone Duo about 10 percent behind iPhone 18 Pro in 3DMark Steel Nomad Light, while Geekbench Metal showed no gap.

HTX Studio also measured a 46.5 degrees C peak for iPhone Duo against 43.8 degrees C for iPhone 18 Pro, and recorded screen brightness falling to 185 nits, per Consomac. Consomac attributes the gap to a smaller vapor chamber and the central hinge limiting how heat spreads.

MacRumors' heat roundup summarizes Mrwhosetheboss's 20-minute stress test: iPhone Duo trapped heat when closed and ran below iPhone 18 Pro Max, though he said the gap wasn't massively noticeable day to day. More in the Mrwhosetheboss video summary.

Against Samsung, iPhone Duo held up better. In Tom's Guide's thermal torture test, a 20-minute 3DMark Wild Life Extreme stress loop, iPhone Duo posted 67.9 percent stability against 51.4 percent for the Galaxy Z Fold 8. Tom's Guide found iPhone Duo warmer to the touch but better at holding its performance, and noted that synthetic results can vary with the task.

Heat in everyday use

Warmth came up in reviews well beyond gaming. MacRumors reports that Joanna Stern ended a FaceTime call because the phone got too hot, and that Apple told her the warmth shows the thermal design moving heat away from the chip. See the Joanna Stern video summary.

The Verge saw heat build during long camera sessions with both displays on, and with Google apps and third-party video apps, enough to cause noticeable lag after a while, per MacRumors. The Verge video summary has more.

Not everyone saw a problem. MacRumors says 9to5Mac found iPhone Duo somewhat hotter than iPhone 18 Pro without affecting performance, and Gizmodo's Wong found the vapor chamber kept it cool enough to avoid lag under full CPU and GPU load.

Macworld's Cross reports the phone gets hot during extended video recording and gaming, and that heat affects performance a little more than on iPhone 18 Pro, though not enough to cause serious issues.

How much RAM does iPhone Duo have?

Apple hasn't said. The spec page doesn't list memory. MacRumors reported that an early Geekbench 7 listing showed a memory figure it says points to 12GB of RAM.

Bottom line

On paper and in short benchmarks, iPhone Duo performs like an iPhone 18 Pro in a folding body. The trade-off is sustained heat: in long gaming and camera sessions, reviewers reported more heat, and HTX Studio measured lower frame rates than iPhone 18 Pro.

If you mostly browse, read and multitask, the reported throttling looks unlikely to matter much, based on these reviews. If long sessions of demanding 3D games are the priority, iPhone 18 Pro or 18 Pro Max looks like the steadier choice on these results; see iPhone Duo vs iPhone 18 Pro. Heavy inner-screen use also costs battery, covered in iPhone Duo battery life.

More on gaming: the best games on iPhone Duo. We'll update this guide as more sustained-load testing is published. Has heat changed how you use your Duo?