On Apple's latest MacBook Pro systems, the dual GPU setup allows for dynamic switching between the onboard and discrete graphics chips to optimize performance and battery life, depending on the tasks at hand. This is convenient; however, Apple does not provide an easy way to manage the different GPUs on the system, and if you like to tinker you may find the utility gfxCardStatus useful, both for newer and older machines.
gfxCardStatus is a small menu extra that displays which graphics card is the active one. When the system's computing demands change and the GPU is switched, this utility will show the switches in real-time, either by displaying an "n" (GeForce 330M) or a "i" (Intel HD) in the menu. If you have the Growl notification system installed, gfxCardStatus will inform you in real-time whenever the graphics processor is changed.
In addition to notifications and alerts, gfxCardStatus will list any processes that are using the current graphics processor, and allow you to manually switch the active GPUs on the system.
While the program is built for the new Core i5 and Core i7 computers, I am able to run it just fine on a Core2 Duo system running the GeForce 9400M/9600M combination; however, it is not supported and claims my system is running the GeForce 330M regardless of what GPU I have running.
Despite this, the program does offer a unique advantage to users of the older MacBook Pro models, in that the GPU switching feature does allow for you to switch GPUs without logging out and closing down your applications. The screen will go blue and then black, but will then reappear and the secondary GPU will be used. This may be convenient for some users; however, it is still an experimental feature so try or use it with caution.
Download gfxCardStatus from the developer's website, it's free!