I thought AHCI didn't work over USB, am I mistaken? I found few positive reassuring links here: How Garbage collection (GC) works: Garbage Collection and TRIM in SSDs Explained - An SSD Primer - The SSD Review Specific to ext usb ssd: Trim on USB3 attached SSD - Page 2 - Windows 7 Forums OCZ Enyo USB 3.0 Portable SSD Review - TechSpot Forums It looks like the answer is GC will work (depend on F/W) but most likely will no be depending on TRIM command which is ATA spec command