What is the max core oc you can get with your default core voltage?
1.70 v ( stock) gives you 1125/ 1575 on AMD Catalyst, which i've had for the past 2 months.
but if you dial in 1229/ 1675 on Trixx, i dont think stock volts is any good any more, so i upped mine to 1.193..... i.e it wouldn't accept those higher figures with 1.7v any more