Try 928/1600 or 957/1650 and drop the core voltage below default. I had a Gigabyte card at some point, memory didn't OC very well. Make sure memory voltage is 1.60V in Afterburner or Trixx, my card defaulted to 1.50V and memory overclocked poorly in general, limiting performance to around 660 Khash. My reference cards are all well above 700 khash with 1015/1750 settings. 0.58 core/mem ratio works best. Intensity 13.