@ANVI
also what settings are you running with those clocks?
--shaders 2048 --intensity 13 --worksize 256 --thread-concurrency 8192 -g 2
These settings seem to work very well with lower memory speeds.
High TC, high intensity, -g 1 require you to overclock heavily.. which is not very good.
If 1030MHz / 1249MHz doesn't work for you, try 919 MHz / 1375MHz. That gives 660 kHash on my sapphire card (reference, not GHz edition).