I'm not sure that is enough, but where do you see UASP support listed? For my Samsung 850 EVO with USB 3 UASP-compatible SATA dock, I still get some serious slowdowns with heavy use. As in down to less than 1 MB/s speeds in extreme cases. If I let it sit for while, the speeds return. I'm guessing that TRIM is not working here (and I don't see TRIM support listed), and it's just taking its time with garbage collection. Does that make any sense?TRIM is supported over USB but the controller for the drive has to support UASP.
OK that makes sense. My dock is UASP enabled, and I do get higher speeds, but I see no evidence of TRIM support.No, UASP provides support for the much-higher speed that an SSD offers - but does not provide trim support. It's still a limitation of the storage support on USB.
You do have to decide if trim is really that relevant now (and is a hurdle that everyone must leap over)
Not everyone agrees.
TRIM is supported over USB but the controller for the drive has to support UASP.
You are correct. USB cannot pass along the SATA TRIM command.
What some people have read and it has caused confusion, is some UASP (USB-attached SCSI protocol) enclosure chipsets can convert the SCSI Unmap command (similar to TRIM) to TRIM commands at the drive. Windows can run this SCSI Unmap command with the Powershell command Optimize-Volume and the -ReTrim option. OS X cannot run the SCSI Unmap command (at least not that I have been able to find). So at this point, no matter what chipset you use, you are not going to get TRIM over USB on a Mac.
There is some discussion at the bottom of this article.