I think that you will find that the answer to your PhysX question is: it depends
The following general information is from PhysX | FAQ | GeForce:
I'd guess that Nvidia's auto PhysX settings are pretty good and their built-in individual game profiles do a pretty good job. That's not to say that you can't tailor some settings for some of your games. Will running PhysX on a GPU slow down gaming performance?
Running physics on the GPU is typically significantly faster than running physics on the CPU, so overall game performance is improved and frame rates can be much faster. However, adding physics can also impact performance in much the same way that anti-aliasing impacts performance. Gamers always enable AA modes if they can because AA makes the game look better. Gamers will similarly enable physics on their GPUs so long as frame rates remain playable. With AA enabled, running physics on a GPU will generally be much faster than running physics on a CPU when AA is enabled. PhysX running on a dedicated GPU allows offloading the PhysX processing from the GPU used for standard graphics rendering, resulting in an optimal usage of processing capabilities in a system.
Can I run NVIDIA PhysX on my motherboard GPU?
NVIDIA PhysX API uses the GPU (Graphics Processing Unit) to process the physics environment calculations in games and applications which support NVIDIA's Physx. Physics calculations can be very complex and therefore as a system requirement, a GPU must feature 256MB of dedicated local video memory, support NVIDIA's CUDA technology and also have 32 cores or higher. If an NVIDIA motherboard GPU or a NVIDIA graphics card does not meet these requirements, you will not be able to use the GPU to process NVIDIA Physx calculations.
Does PhysX scale across the GPU and CPU? If yes, does that mean having a faster CPU enhances PhysX performance or visual quality?
PhysX uses both the CPU and GPU, but generally the most computationally intensive operations are done on the GPU. A CPU upgrade could result in some performance improvement, as would a GPU upgrade, but the relative improvement is very dependent on the initial balance of the system. An optimized PC with the right mix of CPU to GPU horsepower will be the best balanced solution.
Intel and AMD say it’s better to run physics on the CPU. What is NVIDIA’s position?
PhysX runs faster and will deliver more realism by running on the GPU. Running PhysX on a mid-to-high-end GeForce GPU will enable 10-20 times more effects and visual fidelity than physics running on a high-end CPU. Portions of PhysX processing actually run on both the CPU and GPU, leveraging the best of both architectures to deliver the best experience to the user. More importantly, PhysX can scale with the GPU hardware inside your PC. Intel and AMD solutions, which utilize the Havok API, are fixed function only and cannot scale.
How does PhysX support heterogeneous computing?
PhysX shows how heterogeneous computing delivers the best user experience. While the game is running, the PhysX system executes portions of the physical simulation on the CPU and other portions on the parallel processors of the GPU. This ensures all the components of a balanced PC are used efficiently to deliver the best experience.
Check out overclocked GTX 560 SLI reviews and you will find that overclocking your video cards will provide better gaming performance and let you use higher in-game quality settings. Overclocking your cpu should also improve game quality and performance. Keep in mind that the GTX 560 Ti cards are one step up from your GTX 560 cards.
I got excellent SLI results with my overclocked cpu and o/c'd GTX 460 SLI setup with my older cpu/motherboard setup.
Check out my MSI N460GTX Hawk (1GB) Overclocking Results thread to see how much better my system ran.
Hopefully your power supply can handle the additional power requirements and that you have an excellent case cooling setup.
You should find helpful information at Support | GeForce and the Nvidia user forums.
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