The new DX58SO2 bios 0888 contains an updated ICH10 RAID Option ROM (OROM) to version 18.104.22.1689 as per release notes:
This means that it is possible to use Intel RST driver version 22.214.171.1242, which requires (is this really mandatory?) OROM version 126.96.36.1999:
I am waiting for RST 188.8.131.522 to be downloadable directly from Intel's website before upgrading; for now I stay on RST 10.8.
Incidently RST 184.108.40.2069 Alpha Version can be found here: http://www.station-drivers.com/telechargement/intel/sata/11.5.htm .
Since this release mentions OROM version 220.127.116.111, I assumme that Intel will have to release new bios for DX58SO2 in the coming months?
RST 11.5 are supposed to bring TRIM support to SSDs in RAID 0: http://www.tomshardware.com/news/Intel-RST-SSD-TRIM-RAID,14048.html
Hope this is of use to someone.
Some more info:
What a coincidence: Just yesterday I was bemoaning that RST 11.0 WHQL drivers were still not downloadable directly from Intel web-site and lo and behold, they are available today, even certified for the DX58SO2:
I found an interesting article here: