High-capacity versions of the new MacBook Pro aren't affected.

Apple's new 13-inch MacBook Pro uses the M2 chip, which is a major change from the M1 model it launched in 2020, but it isn't the only one.

YouTubers on the Max Tech and Created Tech channels (via MacRumors) conducted a speed test on the M2 MacBook Pro's 256GB SSD and found that it performs half as fast as the M1 MacBook Pro's 256GB SSD.

A sustained disk read speed test performed by Max Tech using the BlackMagic Disk Speed Test showed a drop from approximately 2,900MB/s in the M1 MacBook Pro to 1,446MB/s in the M2 MacBook Pro.

A smaller but still significant drop in write speeds occurred from 2,215MB/s in the M1 Pro to 1,463MB/s in the M2 Pro.

It appears that the NAND flash configuration is to blame. The two YouTubers took the bottom off the new MacBook Pro to find that the 256GB versions use just one NAND flash chip, whereas the M1 model uses a pair of 128GB flash chips.

SSD controllers use a process known as interleaving to read data from and write data to multiple physical NAND chips simultaneously on drives with more NAND chips. You can limit your peak performance by using fewer chips.

While this is an unfortunate problem for those who buy the cheapest MacBook Pro, it isn't unique to Apple. The maximum speeds of modern SSDs for PCs typically start at 1TB or 2TB capacities.

Using high-density NAND chips, you can fit 4TB of storage in a drive that's just a bit bigger than a stick of gum. One unfortunate side effect of increased density is a reduction in performance at lower capacities.

With 512GB and 1TB capacity, the new MacBook Pro appears to offer SSD speeds similar to the M1 version, so if you already bought more storage, you won't have to worry about these performance issues.

Whether the new MacBook Air with M2 will have the same issues at 256GB remains to be seen, though Apple is unlikely to ship a 256GB Air-branded laptop that performs better than a similarly configured Pro-branded laptop.