Also from ocn.
"It is the way to set your max stable oc to the last clock of the boost table, and then setting all values in the voltage table that are LARGER than your max allotted (or available) voltage to your max allotted (or available) voltage. In other words: You would then adjust the voltage table because if you do NOT, the entire voltage table is not being used. Here just an example: Some cards are voltage limited and can only supply a max of 1.212V (which is plenty, by the way). HOWEVER, example, say, in your voltage table, CLK73 has 1275.0V -1281.3V. It would never jump to this entry since this voltage is already far out of range of your available voltage! By adjusting those values which are HIGHER than your max voltage you make it so that your entire voltage table is actually available."
This also cinfirms my thoughts that the card could never boost to 74.
Are you using ref card varkanoid or amp? I suspect ref as amp bios should bevidentical to mine which would suggest amp is more limited than ref for some reason.
Look at you voltage minimum for entry 74 on your bios. I suspect it is below or at 1250mv mine is at 1281mv which is a voltage i cant provide to the card without a bios edit. I suspect they closed off those entries for a reason but why.....