Radeon HD 3800 series suffers from a slight limitation right now. There’s a huge brick wall stopping the GPU from going past 862 MHz. No one has been certain of why that is, but over at XtremeSystems, forum user The Stilt has posted both the answer and a solution (or at least a part of it). The problem is that the PLL VCO divider goes nuts when you hit 862 MHz. The fix is a new BIOS. Unfortunately there is no flash tool with support for the Radeon HD 3800 series yet, but you should keep track of the thread over at XtremeSystems if you want to go beyond 862 MHz with your new Radeon HD 3800 (RV670) card anytime soon.
