gigabyte ati 4770 help volt mod with rbe causing problem

hey ive been trying to oc my gpu with riva tuner and got clocks around gpu/880 and mem around 900 but it wasnt stable sometimes it just crashes at first sight of 3D rendering and i thaught it wasnt enough so i read about volt mod and tried rbe set the voltages to 1.3 and sudenly it velt like my card was slower and i couldnt clock it any more riva tuner ,cpuid says my clocks are core is 750 and memory is 799 ,riva tuner says core is 1500 and mem 796 where did i go wrong please somone help me

its a gv-r447ud-1gi

 

ok wow your stupid rbe screws up my grafix card and not one of u can help me :shadedshu