I have the sapphire 512mb version, i use/used riva tuner to overclock mine. Gpu 830mhz Stock being 750 Memory 1200mhz Stock being 1000 And use either
occt gpu test, or fur mark to check for artifacts and for heat. Best bet is to clock one at a time, finding the limit of both, then trying the combo out. I went up in 5mhz Steps untill it started artifacting.