here's an overview.
 
"The Revo 3 X2 tilizes OCZ proprietary VCA 2.0 (Virtualized Controller Architecture) which provides features including TRIM and SMART data monitoring. This follow up to VCA presents as a complete storage subsystem, but with an improved and expanded feature-set allowing users unprecedented flexibility and industry-leading performance and reliability.Though the Rev03 card supports TRIM, because the architecture is based on SCSI, the Microsoft Windows StorPort architecture currently does not support either TRIM or SCSI UNMAP. As such, these commands are not generated by the OS, which of course prevents VCA from executing them. OCZ is working with Microsoft to have this functionality enabled as soon as possible"