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iPhone Duo Cooling Sends Heat Through the Hinge
Apple’s iPhone Duo cooling system uses flexible graphite routed through the hinge to spread heat between both halves of the foldable.
Apple engineers explained the design in a PCMag interview, adding detail to the iPhone Duo announcement.
A20 Pro adds a second display engine
Apple’s team says the iPhone Duo’s A20 Pro adds a second display engine to drive both screens at once. It is a variation of the chip in iPhone 18 Pro models.
The change supports the foldable’s two-screen design. It doesn’t establish that the Duo is faster than an iPhone 18 Pro simply because its chip is modified.
How iPhone Duo cooling moves heat
The engineers describe four parts of the cooling system:
| Part of the design | How it helps |
|---|---|
| Memory beside the processor | RAM sits next to the main chip instead of above it, opening a more direct path for heat to leave. |
| Metal over foam | A flexible thermal connection transfers heat from the chip to the vapor chamber. |
| A thinner vapor chamber | The Duo uses a different, thinner chamber than the iPhone 18 Pro, positioned within the foldable’s body. |
| Graphite through the hinge | A flexible graphite connection carries heat between the phone’s two halves. |
Apple’s thermal team says the hinge’s graphite connection must withstand repeated folding while continuing to transfer heat.
Apple’s performance claim needs the right comparison
Apple says the A20 Pro and thermal system deliver up to 35 percent better sustained performance than iPhone 17 Pro. Sustained performance means how well a device keeps working during a longer task, rather than a short burst of speed.
The comparison is with the previous-generation Pro, not the iPhone 18 Pro or Pro Max. The figure is Apple’s claim, rather than an Eventide Gaming test result, and it doesn’t promise that every game will gain the same amount.
For gamers, the useful questions are how steady frame rates stay during longer sessions and how comfortable the phone feels to hold. A design that moves heat away from the chip doesn’t, by itself, tell us how warm the outside will feel.
Our iPhone Duo Progressive Review follows the phone from preorder onward, with gaming and heat among the areas planned for testing.
