Every game I happen to run on my msi gtx 660ti pe with the overclock I have set 1254.2mhz core, 1800mhz memory has worked with every game since day one of setting the overclock values. Now I did run across some clocks that would work as high as 1306mhz in furmark for 24 hour stress test runs, but in certain games it would crash, so i just set it back 50mhz and it hasn't crashed since. My memory also worked at 1900mhz on half the games I play, the other half I experienced artifacting so I set it back 100mhz. I only spent one long day (5-7hours) tweaking and fine tuning and ever since that day the card has worked perfectly.