well i use 2 of the fan headers on my x38 , with my clock @ fsb500x9 5:6 without issues. been running those clocks since i got the mobo to.

im using the one next to the nb for a fan on my pwm & one of the lower headers for my side panel fan. the side panel one shows up as system in smartg.

means i can get control over both of them using smartg.