Overview
- Benchmarks published Sept. 21–22 by HOMOLAB and reported by multiple outlets confirm Apple placed QLC flash in many 1TB and 2TB iPhone 18 Pro and Pro Max units while 256GB and 512GB models use faster TLC.
- HOMOLAB’s FIO runs show a fast SLC cache delivering bursts above 3,000 MB/s followed by a secondary buffer near 578 MB/s and then raw QLC write phases that averaged about 79.4 MB/s with occasional drops as low as 1.1 MB/s in extreme synthetic runs.
- Low-queue-depth tests found the TLC 512GB model outperformed the 1TB QLC unit by roughly 38% in Q1T1 benchmarks, meaning some everyday tasks that use single-threaded writes run measurably faster on lower-capacity phones.
- Available free space strongly affects cache behavior because the SLC cache shrinks as the drive fills, and tests at 60% capacity showed the cache falling from about 250GB to near 58GB with sustained-write speeds then dropping to tens of megabytes per second.
- Most users will not hit these worst-case results during normal use, but creators who record long ProRes/4K sessions, move multi‑hundred‑gigabyte transfers, or restore full backups may see meaningful slowdowns and should plan workflows or offload files accordingly.