I have my processor overclocked to 3.88GHz and it's running stable at ~75C (full load). Now I'm interested in overclocking my GTX470 to get a little extra performance out of it. Currently, my 470 runs at ~90C (full load) at stock settings. Is this normal? What do I need to do to overclock and should I consider additional cooling, if so what do you recommend?

Thanks in advanced.