Amorphous in the following thread suggested removing the above file in a step for troubleshooting slowdowns while having PhysX support enabled in Mirror's Edge, though concerning a very different hardware setup. He didn't explain why that file would make a difference, but I think I've figured out why I've been plagued with slowdowns in this game for a long while.

Link

Here's my important system specs:

Intel Core i7 920 @3.0ghz
Gigabyte GA-EX58-UDR3
6GB of Corsair 10666 DDR3
EVGA GTX 275 w/ 896MB
EVGA 8800GTS SC w/ 640MB (old card now dedicated physx)
SoundBlaster Xfi Xtrememusic


I've formatted several times and installed Vista 64 and the Win 7 RC, with generally the same results. With the exception of a couple flukes where the game ran flawlessly with PhysX on in this setup (and going back to terrible performance inexpicably, possibly after a reboot), the game would nearly halt in certain areas when PhysX was enabled on either card. Of course, the game ran perfectly with PhysX switched off. After running across the above thread and not initially considering what Amorphous suggested in the post in question, I came back to it and tried it for the hell of it, and the game worked fine with PhysX on thereafter.

I should have noticed this before when looking at the PhysX files in the game directory, but I'm guessing that the PhysXDevice.dll file is actually the software emulation file that allows the CPU to do the PhysX work if a capable card is not available. I've seen files in the past for other software containing 'device' in the name that were used for emulation, and now I feel silly for not having noticed that earlier. For whatever crappy reason, Mirror's Edge, at least on my machine, defaults to using THAT file, regardless whether or not I have a PhysX capable card. Delete or rename the file, and now it works fine.

Anyone else having problems with enormous slowdowns in PhysX intensive areas, such as after the first interaction with Kate in the prologue, do what Amorphous suggested and rename the PhysXDevice.DLL to something else, and test again with PhysX still enabled. It's possible that this is an isolated solution for myself, but having read so many posts with similar problems, this definitely makes sense.

Development here - may have been a reboot since last night, but decided to jump on ME again and play a bit. Except, it was crawling again in PhysX intensive areas. Exited, checked the \Binaries directory, and the device file still had the extension I replaced as .bak, so I decided to rename PhysXCore.DLL to .BAK. ME + PhysX again works flawlessly.

Can anyone explain this to me? Best I can figure is that when a necessary physx DLL is missing, it defaults to the ones installed under the AGEIA directory in \Program Files, but that doesn't explain why the game worked fine after renaming the first file, then it not working again after a reboot.

Thanks.