M2 MacBook Pro’s 256GB SSD is only about half as fast as the M1 version’s

The use of the M2 chip is the new 13-inch MacBook Pro’s biggest change compared to the M1 version Apple launched in 2020, but it’s apparently not the only one. YouTubers on the Max Tech and Created Tech channels (via MacRumors) have run speed tests on the 256GB version of the M2 MacBook Pro and discovered that the SSD’s read and write speeds are as much as 50 percent slower than the 256GB SSD in the M1 MacBook Pro.

Sustained disk read speeds run by Max Tech using the BlackMagic Disk Speed Test showed a drop from about 2,900MB/s in the M1 MacBook Pro to 1,446MB/s in the M2 MacBook Pro. Write speeds dropped from 2,215MB/s in the M1 Pro to 1,463MB/s in the M2 Pro, a smaller but still significant drop.

The culprit appears to be the NAND flash configuration. Both YouTubers took the bottom off of the new MacBook Pro and discovered that the 256GB versions use just one 256GB NAND flash chip, whereas the M1 MacBook Pro uses a pair of 128GB flash chips. On drives with more physical NAND chips, SSD controllers use a process called interleaving to read data from and write data to multiple physical chips at once. Use fewer chips, and you can limit your peak performance.

While unfortunate for anyone who buys the cheapest version of the MacBook Pro, this problem isn’t unique to Apple. Many modern SSDs for PCs only offer their maximum rated speeds starting at the 1TB or 2TB capacities. Higher-density NAND chips can increase your maximum capacity, making it possible to fit 4TB of storage in a drive that’s just a bit bigger than a stick of gum. But speed drops at lower capacities are one unfortunate side effect of increased density.

The higher-capacity 512GB and 1TB versions of the new MacBook Pro appear to offer SSD speeds similar to the M1 version, so if you were already springing for more storage, you won’t have to deal with these performance issues. It remains to be seen whether the new M2-equipped MacBook Air will have the same issues at 256GB, though it’s hard to imagine Apple shipping a 256GB Air-branded laptop that performs better than a similarly configured Pro-branded laptop.

https://arstechnica.com/?p=1863004