trying to get this zotac gtx 560 to a 1ghz core overclock, its 820mhz stock, i cant get it stable past 900mhz, it crashes in games/benchmarking apps. ive tried upping the voltage and even at 1.1v it wont pull through? the max is 1.15v should i try that voltage setting? many websites have gotten their cards up into the 900-1000+ range but i cant get mine past 900mhz core clock. any tips?