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Mafia 2 PhysX: Dedicated PhysX card vs no card

Mafia 2 PhysX: Dedicated PhysX card vs no card

First up is testing Mafia 2 the way it's meant to be played, as Nvidia would have it; by strapping a brand new GTX 460 768MB graphics card to a previous generation dedicated PhysX card; which in our case is a GeForce GTX 275.

We've compared this to a lone GTX 460 with PhysX set to use the GPU and also CPU, along with a Radeon HD 5870 1GB using CPU PhysX for comparison.

The extra graphics settings like 0xAA and 16xAF were set in-game and a resolution of 1920x1080 was used. Ambient Occlusion was enabled, vSync disabled and all other detail settings put to their highest level. The only exception was the APEX PhysX options of High, Medium and Off, which were changed as shown in the graph legends below.

Mafia II Benchmark - GTX 460

1920x1080, 0xAA, 16xAF, in-game benchmark

  • GeForce GTX 460 768MB (+ GTX 275 PhysX)
  • GeForce GTX 460 768MB (GPU PhysX)
  • GeForce GTX 460 768MB (CPU PhysX)
  • Radeon HD 5870 1GB (CPU PhysX)
    • 47
    • 53
    • 61
    • 34
    • 40
    • 62
    • 18
    • 23
    • 60
    • 13
    • 24
    • 83
0
10
20
30
40
50
60
70
80
90
Average FPS
  • High
  • Medium
  • Off

When the Apex PhysX option is switched off the GTX 460 768MB performs at an average frame rate of between 60-62fps regardless of setup. When GPU PhysX is enabled over CPU, we see a huge decrease in performance of 62 and 70 per cent for the medium and high settings respectively when compared to no PhysX. Having the GTX 460 simultaneously handle PhsyX and rendering is much more favourable, but PhysX still causes a sharp drop in performance, with the average frame rate dropping to 40fps using medium PhysX detail and down to 34fps under high PhysX detail.

Adding a dedicated PhysX card into the system improves the situation dramatically, and with a GTX 275 handling the PhysX workload the average frame rate drops by just 8fps when using medium PhysX detail and by 14fps using high PhysX detail. This equates to drops of 13 and 23 per cent respectively.

There's two schools of thought on this outcome. One is that adding a second graphics card for dedicated PhysX, despite improving performance some 28 per cent when PhysX detail is set to high, is an expensive and, outside of PhysX circumstances, largely redundant addition. That money could have been better put towards a single, faster GTX 470-480 or second GTX 460 for SLI.

However, the other way to see it is that with a dedicated PhysX card there's only an 8fps drop between completely off and medium, and only a 14fps when PhysX is bumped to high. Versus the more powerful alternative Radeon HD 5870 1GB there's a huge advantage when PhysX is enabled, although, with APEX PhysX off entirely, the Radeon's core performance advantage (at twice the price) is 34 per cent faster again.

It depends on your perception and need for the in-game physics, which is extremely difficult to quantify without actually seeing it for yourself. It's a very personal feeling on how you play and enjoy this, or, in fact any game.

With these numbers under our belts, we were curious as to the effect of switching the GTX 460 and GTX 275 around in thier roles. Would the GTX 460 768MB serve better as a dedicated PhsyX processor?

Mafia II Benchmark - GTX 275

1920x1080, 0xAA, 16xAF, in-game benchmark

  • GeForce GTX 275 896MB (+GTX 460 PhysX)
  • GeForce GTX 275 896MB (GPU PhysX)
  • GeForce GTX 275 896MB (CPU PhysX)
  • Radeon HD 5870 1GB (CPU PhysX)
    • 37
    • 42
    • 58
    • 29
    • 34
    • 58
    • 14
    • 25
    • 58
    • 13
    • 24
    • 83
0
10
20
30
40
50
60
70
80
90
Average FPS
  • High
  • Medium
  • Off

Surprisingly there's not that much difference in average frame rate between between the GTX 275 and GTX 460 with APEX PhysX turned off . With the CPU PhysX set in the drivers, the GTX 275 performs almost identically to the Radeon HD 5870, indicating a possible CPU limitation.

Turning GPU PhysX on in the drivers (but not adding a second, dedicated card) gives the expected frame rate boost with medium and high APEX PhysX settings. At 29fps with high PhysX detail the GTX 275 is almost fast enough to run at the high APEX PhysX setting, but clearly the GTX 460 has the egde when it comes to being the primary rendering card.

With the possible CPU limitation's we've uncovered in mind - we decided to test how PhysX in Mafia 2 uses the CPU.