Ok,that's great,i didnt know your board have Marvell 9182.That is the biggest score with AS-SSD benchmark on Marvell controller.
Your board have Marvell 9182 and not 9128.
So,9182 is connected with two pci-e line and that's why your score is close to Intel sata3 when it comes to seq. numbers
This is maximum what i got on Marvell 9128(only one pci-e line) with overclock pci-e line to 110mhz.
This is maximum what i got with AS Media 1061 pci-e card:
If you overclock your pci-e to 108mhz you will get 520mb/s without question,of course if you have possibility to overclock it in bios.
Also you can try this for better 4k:
Change this to bypass.
Also GREAT access times for Marvell controller,some saying Marvell 9128 and 9182 are not fast and stable like Intel sata2 but i would not agree.Why,because my M4 was whole six months on it and i never had problem and boot time was noticeable faster on Marvell.Only thing that i would never do on Marvell is install Windows(maybe i am wrong).But i always did that on Intel port.
P.S.I didnt tell you mb/s will go up with Intel RST,because it cant, its Intel sata2 connection.I said you will see more responsive system and faster boot.
Also,that is still half of performance what you get on Intel sata3 with that SSD(1200 in AS-SSD).But your configuration is great and i would not bother to spend on sata3 platform when getting another SSD for RAID is cheaper.Edited by Unit Igor - 9/13/13 at 1:58pm