First and most obvious you’re going to need an X1800XL. We are using the reference board sent to us by ATI. All of the R520 GPU’s come from ATI and that’s the only thing that we can promise. It’s up to the board partners on what type of memory will be used and how closely they will follow the reference design set by ATI. This is very important to keep in mind as this will affect your results. Another thing to remember is that no card, GPU, or memory will clock the exact same as another. It’s all in the luck of the draw. What I can tell you is that the results we provide here today are very similar to many others around the web.
ATI Radeon X1800 XL Overclocking
Source: Legit Reviews
Legit Reviews has an article online today that looks at overclocking an ATI X1800 XL well past its 500/500 stock speed.