Apple's A20 Pro widens iPhone memory bandwidth 50%

Apple's A20 Pro, detailed in the r/LocalLLaMA thread on the reveal, is the first 2nm smartphone chip. It widens the memory bus from 64-bit to 96-bit LPDDR5X, moving bandwidth to about 115.2 GB/s, a 50% increase over the A19 Pro. Neural Engine cores double too, to 32, up from 16.

The bus width is what got r/LocalLLaMA's attention, not the core count. Running a language model on a phone is a memory-bandwidth problem, not a compute problem. Decode speed depends on how fast the chip pulls model weights from memory for each token, more than on raw operation count. Apple could have kept the narrower bus and added GPU cores instead, for a cheaper spec bump. It didn't.

Widening a memory bus on a 2nm process is not a cheap change. More bus width means more die area, more power routing, more validation work, all for a spec that mainly matters if you're running large models locally rather than sending them to a server. Doubling the Neural Engine core count fits the same story: more dedicated silicon for running models on the device itself.

The announcement doesn't say which models Apple expects to run at that bandwidth, or whether third-party apps get the same access to the wider memory path that Apple's own on-device features get. Developers building local inference for iOS won't know the real ceiling until someone benchmarks a specific model on the A20 Pro and reports tokens per second.