ATI will let its partners overclock their Radeon X1800XT cards to ship out a 'new' card called the X1800XT OC. This graphics card will have a special BIOS and will be shipped with a special software tool to overclock it out of the box to 700MHz core and 1600MHz memory.
We know that ATI's key partners will be able to ship those cards and you can expect them in early December. We don’t know if this is going to be enough to overtake the new Geforce 7800 GTX 512 - we think probably not, but it will make ATI look much better and more competitive.Source: The Inquirer.
Almost any shipped Radeon X1800XT will work at 700/1600 MHz if not more. We also know that retail cards can overclock much more than the press samples that selected members of the press received in early October as the chips are better, I guess.