[QUOTE=Holmer;3304599]
My memory use Samsung IC, their SPD is 8-8-8-24-2T at 1.8V.

You can try this at your own risk of course. But take your ram voltage up to 1.9 .I found with my ram and this board it would not even boot at the rated 1.9 volts but if i take it to 2.04 it boots fine. I do have a differant kit and i can overvolt to 2.1 and not void my warrenty ..So thats why i say do so at your own risk. You say they both work by them selfs in the b/2 slots but what about by them selfs in the a/2 slot what are the results from doing that ? If they dont work in that slot by them self. Might be something wrong with your mobo and adding voltage i doubt would fix it.