The ATI Radeon X1600 graphics card inside each MacBook Pro is capable of running both its graphics processing unit and memory at about 470MHz, but avid computer users have discovered the cards are underclocked to 310MHz (GPU) and 278MHz (RAM).
The modifications cripple the speed of the graphics processor by about 34 percent and the memory by 41 percent.
Users discovered the change after installing Microsoft's Windows XP (with the help of Apple's Boot Camp software) and running a third party application called ATITool (0.25).
By sacrificing graphics performance, Apple was able to improve the MacBook Pro's battery life and keep the units near-silent.
Some daring MacBook Pro users successfully used the third party ATITool software to uncap the full potential of the ATI chip. They found it reduced the battery life of their MacBook Pro by about 30 minutes, but did not over heat the notebooks or cause any other side effects such as display artifacts.
However, one user said the uncapping "took only couple of seconds" to cause the system's cooling system fan to spin at a speed he "never experienced before."