The Trim command can be issued to compatible solid-state drives to tell them which data are no longer considered in use and so can be erased by the drive itself.
This essentially ensures subsequent writes can be made to blocks the SSD knows to be empty, saving it from having to check and, if necessary, erase the block before writing the new data.
The upshot: faster writes and no performance degradation over time, because blocks marked empty actually are empty.
Apple add the Trim command to the version of Mac OS X 10.6 Snow Leopard code for the latest MacBook Pros, released earlier this year and which have SSD build-to-order options.
Older SSD-equipped Macs, including the SSD-only Airs, lacked Trim support until last week's release of Mac OS X 10.6.8, Air-owning forum posters at MacRumors have discovered.
Across-the-range Trim support wasn't previously expected to debut until Mac OS X 10.7 Lion.
Do the Air drives also support Trim? Seemingly so, according to readouts from OS X's System Profiler app. ®