someone must know this come on......,
AGP voltage in the bios does not work the same on a video card as it does a cpu. Change "AGP Voltage" back to the bios default right away. You could shorten the life of your card and mobo. Just a few cards need a slight bump in AGP voltage to increase stability. It will not increase your overclock, and will probably lower it.
What you're looking for is to flash the vga bios to a higher voltage (i think stock is 1.3volts). Type "6800 bios flash" into the search and see what you find.
some dude sais this is it right????