Legit Reviews posted an ATI X1800 XL overclocking guide
Wow! By overclocking our ATI X1800 XL have reached the same core speed as the X1800XT, though the memory would not clock up to the 750MHz of the XT. Trying to go any higher meant that we would need more voltage, and created more heat than we were willing to accept...ATI X1800XL Video Card Overclocking Guide
