Depends on the memory, some will over clock very well, some will not. I have some Patriot DDR-2 667 that runs at 800. I also have some G.Skill DDR-2 800 that runs well at 900. Mine will do this without upping the volts. See if you can find out what kind of memory you have, brand as well as specs & see if there is any info out there about them.