Overview
- Independent testing highlighted by NotebookCheck and AppleInsider found the 1TB iPhone 18 Pro Max uses QLC flash and trails the 512GB TLC model in low queue‑depth sequential benchmarks, for example scoring about 8,168 versus 11,285 in a Q1T1 test.
- Prolonged write experiments showed speeds can fall from hundreds or thousands of megabytes per second while caches are available to tens of MB/s and in extreme, cache‑exhausted runs to single‑digit MB/s.
- Apple uses a tiered caching system that writes first to a small SLC cache and then to a TLC‑speed buffer, and testers found those buffers shrink as free space drops, for example an SLC cache estimate falling from around 250GB to about 58GB at higher fill levels.
- Most daily tasks and short bursts of activity should stay within the fast caches, so normal users are unlikely to hit the worst‑case slowdowns, but long continuous workloads like extended high‑bitrate video recording or massive file transfers could expose the limits.
- QLC trade‑offs mean higher capacity at lower cost but lower sustained write speed and endurance, so buyers should weigh capacity needs against potential heavy‑use performance and reviewers should test long recording and bulk transfer scenarios going forward.