This graph actually shows memory performance compared to actual CPU bus speed set with 4-4-4- timings 1:1. As you see there is a marked dip in memory performance at 400fsb where the chipset clock speed dips, infact you have to go back to 360fsb/1067 strap to see the same performance from the dimms which shows the 1067 strap is MUCH faster than the 1333 on this motherboard. Now the graph is quite linear and around 470fsb you see memory performace now matches whats is seen at the top end of the 1067 strap, the only issue is it is now stable where under the 1067 strap at 399fsb you probably will see some instability issues. From 467fsb onwards you will now see the highest performace from your dimms although you are relying on how good the NB overclocks under the 1333 strap.