I run 400x9 4:5 to get 500mhz.

I run 400 so my CPU kicks down to 2400Mhz at idle and only uses 1.1-1.2 volts. Works like a dream. If I did 500 1:1 I'd only kick down to 3000Mhz. The TDP is quite different between 2400 1.15v and 3600 1.35v

Anyway I'm rock solid at 500 5-5-5-3-15 2.0v. I needed an upgrade from my 2Gb Ballistix because I was getting memory errors in Photoshop. At first they wouldn't boot, but a quick jump on here found that I needed to change my tRFC to 55. The Ballistix liked 30 at the same 500mhz 5-5-5-15 2.0v setting.

My other timings are:

4
55
6
14
11
3
8
5
4
2600T
2T