Need 4 dual rank sticks of ram for optimal bandwidth, VictorWang.

I've got 4x1GB Kingston ValueRam 667mhz FB-DIMM's but mine stop at 400mhz... figuring out vdimm mod on my X7DAL-E still. Have VNB figured out I think, but FB-DIMM's are limiting, not northbridge (other than heat, 80c+ without directed air) as far as I can tell.