Apple's priciest iPhone gets slower storage at 1TB, just like the iPhone 18 Pro Max

Weibo tech blogger WHYLAB has posted a photo of an iPhone Duo running a third-party iOS diagnostics app that reports component suppliers. The app identifies the unit's storage as 1TB of SK Hynix QLC (quad-level cell) NAND. According to WHYLAB, only the 256GB and 512GB iPhone Duo configurations use TLC (triple-level cell) NAND, which would put the 2TB model on QLC as well. The photo shows only a 1TB unit.

The split mirrors what Bilibili channel HOMOLAB found when it tested the 1TB iPhone 18 Pro Max's QLC storage last month. In its FIO benchmarks, the phone's SLC cache handled bursts above 3,000 MB/s. Once that cache and a secondary TLC-like buffer were exhausted, raw QLC writes averaged 79.4 MB/s and dropped as low as 25.6 MB/s.

With the drive 60% full, the SLC cache shrank from around 250GB to 58GB, and raw QLC writes averaged 45 MB/s with a floor of 1.1 MB/s. The iPhone Duo uses the same A20 Pro chip as the iPhone 18 Pro models, but its storage has not yet been benchmarked, so its cache sizes and sustained write speeds remain unconfirmed.

The readout comes from a third-party app and has not been independently verified. Apple does not list NAND cell types in its specifications, and it typically sources storage from multiple suppliers, so components may vary between units.

The iPhone Duo went on sale on October 23. It starts at $1,999 for 256GB, with the 512GB, 1TB, and 2TB models priced at $2,199, $2,599, and $3,199, respectively. The step from 512GB to 1TB adds $400, the same upcharge as on the iPhone 18 Pro Max.