After searching the web for information or reports, I have decided to install ATI tools for WinXP on my MBPro; but the version 0.24 was not working...Having a MBPro, I have repeated the operation.
Then I successfully installed ATI optimized drivers to replace those ones provided by Apple, then I installed ATI Tools beta version 0.25...
And I immediately came to the conclusion that once again Apple dramatically underclocked the GPU of its notebook models. Indeed the Radeon X1600 in the MBPro is clocked a 310MHz / 278MHz (GPU and RAM respectively)!
When looking on the web, I have found that many PC notebooks featuring this GPU have a 470MHz/470MHz setting...
Then I decided to increase the clockspeed settings of the ATI Radeon X1600 located in my MBPro, while carefully checking heat release and side effects/display artifacts...
And as a big surprise: no artifacts and huge performance gain!! When using Counter Strike source benchmarks (all settings to the max and definition at 1440x900) FPS jumped from 61 to 97!
I have been able to install the ATI Tools beta version 0.25 R14 without changing drivers as SpacetitoX did; and indeed the settings are far below those ones recommended by ATI: 475MHz for the GPU, 470MHz for the RAM.
I also did not notice any artifacts, but it took only couple of seconds to turn one the cooling system fan to a rotation speed that I have never experienced before even when performing CPU intensive tests. It is clear that Apple has underclocked the GPU of the MBPro to keep the machine as silent as possible; and also to keep a battery lifespan similar to the PBG4 (eventhough overclocking the GPU only reduced battery lifespan by 30 minutes).
We are waiting for the next release of ATIccelerator that should support this GPU. It will be interesting to increase on-the-fly the frequency of this GPU in order to improve performance for GPU-consuming games such a Quake 4 or Doom3.
Keep in mind, that if you try to repeat this hack we will not be responsible for any damage that might arise to your machine.
Last points, ATITools 0.25 is relatively not stable when using the original Apple's drivers.