Once settles the compatibility problems of a PC Radeon HD4890 in a Mac Pro, we have been looking at its ability to be overclocked. After the installation procedure described yesterday, it was rather simple to modify the BIOS located in the plist extension to overclock the card without flashing it. We have successfully pushed the GPU frequency to 920 MHz (vs. 850 MHz originally) and 1080 MHz for the memory (vs 975 MHz).
The performance gain of such overclock is between 8 to 9%, if this is not huge, it might not be negligible when considering the potential of this card. If the card perfectly supported such overclocked, our ears noticed the difference. The card is already a bit noisy when loading it with 3D associated tasks, but when overclocked, event 2D tasks makes it more than audible. In other words, if the overclock was a piece of cake, the integrated cooling system is then quickly overloaded and definitely not designed for such operation. We will try in the future to adapt a better cooling system able to fit into the Mac Pro.
