pllsss Help

I have MB asus P5WD2 and X1800XL and very good watercooling (all swiftech) and when I overclock FSB more than 250 the screen begin to blink even ATI Catlist Control Center > 3D > test -car -car is blinking .

BUT when I increase FSB Termination Voltage everything is OK --but it is only possible ot FSB 260

Which MOD i should to do to increase Voltage more than 1,5 to FSB Termination Voltage ( 1,5 is maximum by BIOS)