Mirror's Edge - Physx effects reviewed: Benchmark sequence
To check how the additional physics effects make themselves felt, we use the checkpoint B of the level "Heat”. On ground floor we slide through a corridor, while the SWAT team chasing us blasts nine big glass panes. This is a worst-case scenario.

Mirror's Edge - Physx effects reviewed: Benchmarks with and without additional physics
The fps are directly related to the additional effects. If you have a Geforce 9800 GTX+ or a better card, you should use GPU Physx and the additional effects. This way Mirror's Edge is running noticeably slower, but still quite smooth with a GTX 260-216 for example. If you also use a quad-core instead of a dual-core processor at the same clock speed, you also get about 20 percent more performance.

With a Radeon HS 4870/1G you should better do without the additional effects: As soon as the window panes shatter, the performance is reduced and the fps drop to single digit values - this way Mirror's Edge is unplayable even on a 4.0 GHz quad-core processor. But without the additional effects the DICE title runs smooth although the Radeon doesn't benefit as much from a faster CPU as the Nvidia cards do.

During our benchmarks with the review code, the Radeons were faster than the Geforce cards even with activated physics effects. The reason is simple: The benchmark sequence we used for those tests, didn't use a lot of physics effects.

Mirror's Edge - Physx effects reviewed: Benchmarks with dedicate Geforces as Physx accelerators
Many users ask themselves if a second Geforce as a Physx accelerator increases the performance. Based on the results of a GTX 260-216 with activated GPU Physx it becomes clear: A weak card like the 8400 GS is absolutely overstrained by the additional effects and slows the system down. But even 8600 GT can boost the system by about 15 percent, a 9600 Gt by about 30 percent. If you even use a 9800 GTX+ as Physx card, you can get about 5 percent more.

Mirror's Edge - Physx effects reviewed: Conclusion
The PC exclusive, additional physics effects make Mirror's Edge unique and the game benefits in matters of visualization as well as atmosphere. But practically this statement applies for owner of a Geforce 8 or better graphics card. Mirror's Edge becomes unplayable slow if the physics have to be calculated by the processor. But the additional effects, which can be smoothly displayed with GPU Physx only, are not essential for the gaming experience in Mirror's Edge. If this will change in future title, remains to be seen.