Many overclockers have been noticing that their new RV670 (HD 3850 or HD 3870) based graphics card is hitting a core MHz wall at exactly 862MHz. It was first thought that a driver issue or limitation of the GPU was the cause of it.

However, a clever and persistant fellow over at the XtremeSystems forums didn't buy any of that and continued to dig deeper, eventually coming to realise that the exact 862MHz wall people are experiencing with their cards is due to the PLL VCO divider going haywire once you reach this point.

A newly modified BIOS flash is all that's required to fix the issue, which was also kindly provided by the same person.

What a champ! There's more on this (and how / what to flash with) over at the inquirer as well.