odd overclock issue

[Faction]

my 3700+ has been OC'ed at 2.75 ghz forever without issue.

I recently changed bios and videocards from a 7900GTX to a 7950

now when putting it up to the 2.7-2.75 range the screen gets into windows, everything acts cool but then the screen will flash black all the time, its annoying obviously..

Is it possible that my PSU is not doing its job? or is it possibly the bios i upgraded to?

PSU is 550watt (no idea the amps sorry)
at 2.65 everything runs fine.

 

[nchell]

what brand is your PSU?
7950 surely doubles the wattage than 7900.

 

[(cf)Eclipse]

PSU is 550watt (no idea the amps sorry)

it should say right on it

and it's possible that case temperature has risen, thus lowering your maximum overclock