As you may know, I own an ASRock Z97 Extreme6 mainboard and have done with this Z97 system in January 2015 an extensive Intel RAID0 performance comparison test using different Intel RAID BIOS module/driver combinations (for details look into the chapter B. of >this< thread). All tests were done after a fresh install of Win8.1 x64.

Unfortunately I was not able to test any Intel RAID module/driver combo of the RST v11 or RST(e) v12 line.

Reasons:

1. OS related problem:
   Microsoft's latest Operating Systems Win8/8.1/10 do contain a new generic Intel RST(e) RAID driver v12.0.1.1018 named iaStorAV.sys, which obviously prevents a successful installation of any Intel RST driver v11.x.x.xxxx.
   It was possible to "downgrade" the in-use Intel RAID driver to the Intel RST driver v11.2.0.1006 WHQL by using the "Have Disk" button, but after the following reboot I always got a BSOD. Even booting off the OS installation media using the "Repair" option didn't solve this problem.
   Solution:
   At least I found together with nuhi a way to circumvent this problem and to get any "classical" Intel RST RAID driver like the v11.2.0.1006 properly working with Win8/8.1/10 by
   a) removing the generic Intel RAID driver iaStorAV.sys from the boot.wim and install.wim of the OS image and
   b) integrating the desired Intel RAID driver into the image.
   For details please look into the start post of >this< thread.
2. BIOS related problem:
   The replacement of the Intel RAID ROM module v13.0.0.2075, which had been inserted by ASRock into the latest BIOSes for the Z97 Extreme6 board, by the Intel RAID ROM v11.2.0.1527 worked without any issue, but after having flashed the modded BIOS, set the Intel SATA Controller to "RAID" mode, enabled CSM and forced the LEGACY Option ROM settings, I was not able to get access to the Intel RST RAID Utility v11.2.0.1527. To find out, if this was just an issue with the "classical" Intel RST drivers/OROMs, I inserted the Intel RST(e) RAID ROM/EFI RaidDriver modules v12.9.0.2006 into the BIOS, but I got the same result: No access to the Intel RAID Utility, neither in LEGACY nor in UEFI mode.
   Since I regarded these test results as a BIOS bug, I contacted the ASRock Technical Support and reported about my problem.
   This was the very surprising statement I got from ASRock:
   

   Zitat von ASRock Support

   ---

   Hello,
   
   It is not a bug in the BIOS, but a choice we made, since we don’t want others to modify the BIOS.
   I checked, but It is not possible to create a BIOS with the older version, I am sorry.
   
   Kind regards, mit freundlichen Grussen
   
   Peter
   
   ASRock Europe B.V.
   Bijsterhuizen 11-11
   6546 AR Nijmegen
   The Netherlands

   ---

   
   Solution: I dont know any, but maybe anyone of our Gurus?

@ CodeRush:

Thanks for your statement, which explains, why I was not able to get access to the Intel RST RAID Utitlity v12.9.0.2006 in UEFI mode.
Nevertheless there are still some questions left for me:
1. Is the "AhciMmioSmm driver" the ASRock BIOS module, which is listed by the Aptio MMTool as "AhciSmm" or is it just listed by a GUID?
2. Which function has the AhciMmioSmm driver?
3. What has the AhciMmioSmm driver to do, when the Intel SATA Controller is running in "RAID" mode?
4. Is the AhciMmioSmm driver used/required by the system in LEGACY mode as well?