This may be a question for Samsung, but I figured I'd check here. I have a Dell Precision T3600. It has the C600 Series controller in it. I downloaded and updated the drivers to 3.7.0.1092 (dated 3/19/13). It installs two separate controllers; one SATA AHCI Controller, and then one SAS RAID (Sata Mode).
When I run Samsung Magician software on the installed Samsung 840 Pro 256GB SSD, the write and random write speeds are horribly low (see attached). I'm not sure if these results are just arbitrarily low because of a software glitch, as AS SSD Benchmark posts pretty normal benchmarks for this chipset/drive combo.
I rolled back the driver to 3.1.0.1082 (dated 3/31/2012), it's just picks up the SAS RAID (Sata Mode), and benchmarks across all programs are well aligned with each other.
SSD is plugged into one of the two 6gb/s SATA ports on the board.. I've verified this across three T3600s that we have on site..