Railworks America

I have a nVidia 9500GT passive cooled GPU lying about and thought I'd put it in the third PCI3e slot and dedicate PhysX to it, without using SLI.
This used to work in my old motherboard, paired with a GTX 7something.

On the new VR rig I can still fit the card, but the current nVidia driver doesn't recognize it anymore, it is geared towards 8th, 9th and 10th gen GPU's.
Downgrading the main GPU driver probably isn't the wise option.

Anybody have any ideas? Would a matching passive cooled 9- or 10-series make a good dedicated PhysX processor? Or is PhysX so easy on a 980 or 1080 GPU it won't really matter??

Ed
Just an opinion
The new 10 series cards (and the 9 series) can easily handle PhysX without having to supplement with another separate card.
2 cards could be counterproductive, as the biggest problem with video cards is latency, and having the cpu to address 2 cards to achieve the same result and display the combined data on a monitor, could result in higher latency and reduce performance. The two cards would have to be synchronised to process the data and send it to the monitor and that's not always possible even using SLI.
pH

Pretty much what Peter said.
At some point in the last couple of years, I read that Phys-X on a separate card was no longer necessary.
I tried my old GTX 780 paired with a GTX 560 to offload the Phys-X in TS, but saw no improvement at all.
I just had more fan noise coming from my PC's case.

Note: Some of those older GPUs are no longer supported by Nvidia.

Thanks for your answers.