iPhone 18 Pro Max 1TB and 2TB Models Use Slower QLC Memory
The most expensive iPhone 18 Pro Max configurations switch to QLC flash, resulting in significantly lower sustained write speeds than previous models.
Key points
- The iPhone 18 Pro Max 1TB and 2TB models use QLC flash memory, which is slower than the TLC memory in smaller models.
- Sustained write speeds drop to 79.4MB/s once the fast SLC cache is full, compared to 3,000MB/s during cache writes.
- The 1TB QLC model is 38% slower in 4K random reads than the 512GB TLC model under low-load conditions.
Apple’s latest iPhone 18 Pro and Pro Max models in the 1TB and 2TB tiers use slower QLC flash memory. This change was discovered by Homolab during a detailed comparison of the devices. The finding highlights a performance trade-off in Apple’s most expensive storage options.
The 256GB and 512GB versions continue to use faster TLC memory. However, the higher-capacity models rely on a different, less efficient technology to keep costs down. This shift marks a departure from the iPhone 17 Pro, which used TLC memory even in its largest configurations.
Cache limits reveal speed drop
Apple uses a fast SLC cache to mask the slowness of the underlying QLC storage. In tests, this cache allowed write speeds of up to 3,000MB/s. However, once this temporary buffer fills up, the phone must write directly to the slower QLC memory.
At that point, speeds plummet to 79.4MB/s, with occasional dips to 25.6MB/s. The situation worsens as the phone’s storage fills. When 60% of the space is used, the SLC cache shrinks to just 58GB. This leaves less room for fast writes, forcing more data onto the slow bulk storage.
Real-world impact remains uncertain
Homolab’s tests show the 1TB model is 38% slower in random read tasks. This difference narrows to 12% when multiple processes access data simultaneously. While these are synthetic benchmarks, the gap is significant enough to affect heavy data transfers.
GSMArena notes that real-world usage may feel different from these lab results. However, the drop in sustained write speeds is a clear technical regression. Users paying a premium for 1TB or 2TB storage now get a slower component than those buying the 512GB version.
Cost pressures drive memory choice
Flash memory prices have risen sharply, making high-capacity TLC chips more expensive. Apple likely switched to QLC to manage the cost of the 1TB and 2TB tiers. This decision reflects the current market reality where memory costs are a major factor.
Previously, higher capacity meant better performance because workloads could be split across more chips. That logic holds only when comparing similar memory types. QLC packs more bits per cell, reducing cost but sacrificing speed. Buyers of the top-tier iPhone 18 Pro Max should weigh this trade-off.
