Yesterday, Apple released Mac OS X 10.10.4, providing a number of bug fixes and subtle improvements to the currently shipping version of the desktop operating system. According to Ars Technica, one of those improvements is the addition of support for TRIM on third-party solid state drives (SSDs).
TRIM isn’t something most users worry about; it’s a system-level command that provides communication between the operating system and SSD regarding unused areas of the drive that are ready for erasure and overwriting. Without TRIM, drives can become much slower as more data is added to the device. OS X has supported TRIM for built-in SSDs, but not for third-party drives that were added after the fact. Often, those drives came with proprietary tools to enable TRIM.
10.10.4 includes a command-line utility called trimforce that adds TRIM support. When run, the utility requires a reboot to take effect. Ars Technica’s Lee Hutchinson reports that Apple has added “scary warnings” about using the utility, most likely because not all third-party SSDs operate in the same way and some data could be lost in the process.