I have a AMD Phenom II B55 quad-core, with a single ATI Radeon HD 4890. It's not a beast, but it works well enough to play most games at High if not Ultra. I play skyrim at ultra with grass turned down (i can't find stuff in the grass, not because it hurts performance), and I play BL2 on High across the board at 60+ frames per second, rarely had I ever seen the fps flicker below 60 for more than a couple of seconds.
In your WillowEngine.ini you'll find the line PhysXLevel=x where "x" is 0=low, 1=medium, and 2=high. (Low is basically Off)
As an AMD/ATI graphic card owner, it's auto-set to low and will not give you an option to turn it on within the game's options. Changing the 0 to a 1 or 2 in the ini file does turn up the PhysX for the ATI cards and you get to enjoy all the bloody splats and puffy frills that Nvidia cards show... BUT, it could drop your frames down and slow your computer down since it utilizes the PhysX through your CPU and not your GPU. However, my older ATI card and mid-range CPU handles the PhysX on the High setting just fine. When things get hellish and my screen is full of everything I drop to between 30-50fps which is barely noticeable.
I'm using an ATI Radeon HD 5770. Good, but not great.
@OffCentered: How are you monitoring your FPS in real time?
File version is now 18.104.22.16844 (10/25/2012). There is an announcement on Steam discussing the changes, including patch for the DLC bug.
Thanks for the discussion re: PhysX. I thought it was only available for Nvidia. Nice effects also with ATI (on medium; may try high).
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