Joe,
When RAID mode is enabled, I can install the RST 13.1 on my 6 series board without issue, downloaded directly from Intel. The device manager shows 13.1 as the driver version on my RAID controller.
When I switch to AHCI mode, 13.1 does not install, only 12.9 will install.
Why does the installer for 13.1 install on 6 series in RAID mode if it's not supported?