Update is a little misleading, there is an actual MS written "generic driver" for SATA controllers (well, AHCI actually), if you install the driver from the mobo maker, it will replace that with a driver written by intel, AMD, nvidia, SIS, etc. Those drivers might or might not be newer, but even if newer, they might not be actually better.
The MS drivers were first to support TRIM, followed by intel. the MS driver is also very robust.
This thread discusses it in detail:
http://forums.amd.com/forum/messageview.cfm?catid=383&threadid=126518
with the answer is given by gaspard.leon
Basically there are two issues at stake here:
1. Does the driver support TRIM, at all?
2. How does the driver handle TRIM when in RAID mode?
To answer #1:
MS and intel drivers support TRIM, AFAIK they are they only ones. Windows, Linux, and Solaris support TRIM, MacOS does not.
To answer #2:
No controller supports trim on an SSD that is part of a RAID array, supposedly it is possible, but requires modifications to the controllers (and are sure to cost extra), as of yet nobody offers a controller that can do so.
But there is another issue, Say you have set your controller to "RAID Mode" and have made a RAID1 array of 2x2TB HDDs, and you have your OS on an SSD NOT part of a RAID array. Well, because the CONTROLLER is set to RAID mode that would cause TRIM not to work... with the exception being intel mobo controller that is using the latest intel drivers (it wasn't available at first, but was patched in)
So, what does all this mean to you? In theory you should have working trim by installing windows 7 and not touching the chipset drivers from AMD. And unless they have recently released new drivers that finally support it, installing the AMD chipset drivers will disable your TRIM, so you should NOT install them.