When speaking to a few ATI partners, the word was that ATI had been quite lenient with the clock speeds on the new HD 4890. Since ATI ultimately needed this card to be as fast as possible, it seemed weird that they would hold back slightly on clock rates.
With this in mind, we thought we would take the time to overclock the card. At first we tried Rivatuner but that didn't want to play along with the new card and ATITool had the same issue. In a last minute attempt, we decided on trying the ATI Overdrive utility built into the Catalyst driver suite. Fortunately, this was perfect for us and away we went on our overclocking venture. Increase, benchmark; increase, benchmark; increase, crash; decrease, benchmark. Read more at TweakTown.