This may sound elementary but since i dont know-what multiplier you are using then id drop it even more and up the FSB, till you get what you want, also id definatley lapp the HS on the NorthBridge and use some artic silver2, cant hurt and almost gaureentees a few more mhz in the FSB, which can be the difference in getting to the 1/5 divisor, then you can OC even more cause the other cards and stuff will be running closer to spec, therefore haveing less of a chance to restrict the overall speed.