in the bios you increase the volts to it, but you have to have a motherboard that supports doing this. and ram that can handle the abuse per say.
i'm sorry but i have to correct you on that. increasing the voltage on its own will only increase heat output and unnecessarily shorten the life of the memory.
you should probably repost this in the overclocking section.
basically the memory speed is tied to the processors FSB so you should do some research and learn to understand overclocking in general.