One of the major upgrades with this year’s iPhone 6 and iPhone 6 Plus has been the internal storage capacity. While last year’s iPhone 5s topped out at 64GB, the iPhone 6 and iPhone 6 Plus have a higher 128GB option. The size isn’t the only difference though, Apple has also moved to TLC NAND flash storage on select 64 and 128GB iPhone 6 and 6 Plus models this year. KBench decided to run benchmarks and find out the exact differences between the two types of flash memory.
The results of the benchmark comparison are quite surprising. KBench conducted two tests: Zero Filling and Random Data. The first test overwrites all data stored in the memory with null values (0x00). All data that is stored on the flash memory is deleted permanently, making it impossible to recover the data. A 3.4GB block of data was written on to the memory for this test. The MLC flash memory managed an average transfer rate of around 75MB/s while TLC flash managed to perform much better initially, with transfer speeds reaching 200 MB/s, but the rate dropped to 40MB/s after 800MB data had been transferred. MLC flash was actually slightly faster during the final stage of the test, with transfer speeds hovering between 65 and 75MB/s.
In the Random Data test, MLC outperformed the TLC flash memory consistently. TLC managed transfer speeds of around 3MB/s throughout the test while MLC started with 2.9 MB/s and shot up to 15.7 MB/s near the end. It also turns out that the TLC memory usually has higher RAM usage than MLC NAND. In the tests conducted by KBench, the iPhone 6 with TLC flash memory had 232.8MB inactive memory, while the one with MLC flash had only 109.9MB memory inactive.
So it isn’t just the speed difference, but also higher memory utilization that makes TLC flash a clearly inferior alternative to the more popular MLC flash memory that Apple has used on its iPhones in the past. Recent rumors suggested that Apple could discontinue the use of TLC memory in its products, while we’re not sure how accurate the info is, we do hope Apple will go back to MLC Flash for future iPhones.