you should try to find out a balance point of the VGA Voltage for both cards, usually that is the default voltage(or the max safe voltage) of the less overclockable one, use EVGA percision software, don't overclock to Max in SLI mode, that's my personal experience since 460SLI to 780SLI. recently, some one is trying add Boost 2.0 into GTX 680 by modding the BIOS, it is being tested right now, the finished version should be released in this month, then you might want to try it by taking advantage of the Boost 2.0 thermal control since you use water cooling. link tohe Boost 2.0 BIOS for 680/670 ★★è¯è¯´æˆ‘å·²ç»èƒ½å¤Ÿè®©680/670/660Ti支æŒBoost 2.0★★ - é¡¶çº§å›¾å½¢å¡ - Chiphell - 分享与交æµç”¨æˆ·ä½“éªŒçš„æœ€ä½³å¹³å° - Powered by Discuz!