What OS and which drivers? NVMax is no longer supported and Win2k has an issue that prevents the coolbits mod from "staying set" over 400mhz. There are patches avalible to correct this but none support the 12.90 drivers. Try using Riva Tuner. It works with 12.60 and below but I still lose my settings after the monitor wakes from sleeping.
hope that helps,
kev