Tech support agreed that installing the PERC S300 was the solution to enable AHCI. However, after installing the S300, AHCI was not enabled. Support did some further investigation and found out that the system engineers disabled AHCI on the motherboard. I gather that the other 11G systems are configured similarly. IMO, this is pretty significant issue...PE docs indicate that system supports AHCI & SSDs. Well, SSDs don't function properly without TRIM support and that requires AHCI. Intel confirmed that a single SSD on a RAID controller but not in an array will function as if connected to AHCI. (Intel's next update of the RST drivers will support arrays). But that workaround does no good as cannot install the RST drivers whether BIOS is set to ATA or RAID. Since I purchased the particular model partially-based on AHCI/SSD support, I'm awaiting an answer from customer care on some type of remediation. 
Received a new T310 and have opted to install an SSD.  A number of documents on Dell's site indicate that T310 supports hardware-based AHCI. I have latest BIOS installed but my only SATA options are Off / ATA / RAID. Any guidance is appreciated. 
AHCI on 2012 T310?