The 1TB storage space of iPhone 18 Pro Max has encountered an unexpected test. The HOMOLAB test shows that when the cache is exhausted, the writing speed of the QLC flash drive will drop to a level that can hardly be called a flagship.
During normal tasks, this problem is barely noticeable: the fast SLC cache allows the drive to be overclocked to over 3000 MB/s. But with long recordings, it ends, after which the smartphone switches first to the buffer with a speed of about 578 MB/s, and then to the QLC memory itself. The average speed during this period was only 79.4 MB/s, which dropped to 25.6 MB/s at the peak.
As the tanks filled, the situation got noticeably worse. At 60% capacity, the available SLC cache is reduced from approximately 250 GB to 58 GB, and the intermediate buffer slows to 396 MB/s. The QLC memory itself has an average speed of 45 MB/s, with worst-case speeds dropping to 1.1 MB/s. By comparison, the 512GB iPhone 18 Pro with TLC memory was about 38% faster in mixed workloads at low queue levels.
In everyday use, this is unlikely to be a problem. But when it comes to recording 4K and ProRes for extended periods of time, transferring large files, or restoring backups, owners of the 1 TB version may suddenly find that the massive drive simply doesn’t work as well as the flagship machine.