if its much like my cpu, 2920@1.4v, 2966@1.425, 3000@1.55 - the scaling goes to pot at just over 2966 making the last 33mhz not worth chasing....

the ram should be ok, tho my mem controler gets very funny at the same point at core volts jump - 3000 is much happier with ram on 180 div than 200 div.

try whats been recomeneded already to check the htt limit - it might jsut be the limit of your board/the cpu (very high cold-bug?)