Nvidia PhysX is a leading technology of the graphics giant which accelerates physics and other computational tasks on the GPU. By default, all the new Nvidia graphics cards support PhysX. Recently, Nvidia has disabled the Physics acceleration on its GPUs when an ATI graphics card is used for rendering graphics.
Different graphics cards, either belonging to same company or different manufacturers, can be combined in a gaming system to accelerate graphics. Nvidia supports a configuration where two Nvidia GPUs are combined in parallel on a motherboard and one GPU is used to accelerate physics, whereas the other renders graphics. It is also possible to use a different graphics card, such as by ATI to render the graphics. However, Nvidia has recently disabled support for accelerating physics via PhysX technology in this setup.
Therefore, in order to take advantage of the PhysX technology to work in a dual GPU environment, both the graphics cards should be Nvidia branded. This was revealed in a response by Nvidia explaining the issue on NGOHQ forums. Here’s the response from Nvidia about this matter:
Ill explain why this function was disabled.
Physx is an open software standard any company can freely develop hardware or software that supports it. Nvidia supports GPU accelerated Physx on NVIDIA GPUs while using NVIDIA GPUs for graphics. NVIDIA performs extensive Engineering, Development, and QA work that makes Physx a great experience for customers. For a variety of reasons – some development expense some quality assurance and some business reasons NVIDIA will not support GPU accelerated Physx with NVIDIA GPUs while GPU rendering is happening on non- NVIDIA GPUs. I’m sorry for any inconvenience caused but I hope you can understand.
NVIDIA Customer Care”
It seems the support for PhysX is disabled when an ATI GPU is present primarily due to business reasons rather than development costs. I think if Nvidia advertises its products and technologies, it must enable them in all configurations, letting the end consumers to decide what they like the best!