Uh, what am I doing wrong? (deadicated physX card)

So I have a GTX 770, and decided to use my old GTX 570 as a dedicated PhysX card for Assassin's Creed Black Flag, and experienced no different in FPS whatsoever as I did without the 570.

With dedicated physx card in certain PhysX heavy scenes I get like 17 FPS.
Turning PhysX off in the games configuration menu I get 40+FPS in that same exact scene.

Wtf?

@SystemsGO: Before anyone asks, yes I went in the Nvidia Control panel and set it up as the dedicated PhysX card. Then I reinstalled the 770 drivers.

I'm downloading 570 drivers right now to see if that makes any difference. Will report back.

AC4 is not optimized, find OTHER games to test it such as Mafia 2 or Metro LL.

Regardless of optimization having a GTX 570 as a dedicated PhysX card should NOT produce the same FPS as foricing it all on my CPU or GTX 770. Do you understand what I'm getting at? My point is that perhaps my GTX 570 may not be actually performing as the dedicated PhysX card.

Theoretically, with a GTX 570 as my dedicated PhysX card, PhyX should NOT take a hit on my FPS, in any game. At least that's what one would think.

Besides, I don't feel like reinstalling Metro LL, and to be honest never noticed much in the PhysX department on that game, but my memory could be distorted.

@SystemsGO: Just tested it on Borderlands 2, no difference whatsoever in FPS. Once again.

If you see not climax with temps on the GTX570 then it's not doing anything, if opposite of that well it's working.