FPS drops, don't know why

Hey all. I'd appreciate any input on my situation.

I recently re-installed Doom 3 after years of collecting dust. I noticed when r_multiSamples is set to "4", my FPS becomes unstable, sometimes dropping down to the mid 30's. This is frustrating to me because my video card is a GTX 550 Ti. Shouldn't I be able to run 4x MSAA without FPS drops, considering this game is more than 7 years old? Or is Anti-Aliasing really that taxing with id Tech 4?

With r_multiSamples set to "2", my FPS does not drop - at all. Here are some specs and settings:

Core 2 Duo 2.66 GHz
4 GB DDR2-800
GTX 550 Ti
WinXP Pro 32-bit

1920x1080 res, Ultra settings, r_renderer "ARB2". V-SYNC is OFF

I'm using the 275.33 drivers.

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Why are you on such outdated drivers? NVIDIA's up to 285.58 for that card. You ought to update that first and foremost.

While your GPU isn't bad, I'd say the combination of 1920x1080 resolution and increased AA is what's "killing" your performance.(Though mid-30s certainly isn't bad in any respect.) Everything else is in-check for a 7 year old game (though 32 bit XP? Still?), so I'm definitely calling the resolution and drivers to be the main issue.

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I think there's a fair chance that the Core 2 Duo is bottlenecking the 550 Ti, but take that with a fistful of salt.

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Xeros612 said:

While your GPU isn't bad, I'd say the combination of 1920x1080 resolution and increased AA is what's "killing" your performance.(Though mid-30s certainly isn't bad in any respect.) Everything else is in-check for a 7 year old game (though 32 bit XP? Still?), so I'm definitely calling the resolution and drivers to be the main issue.


Sorry, but my old computer was worse than the OP's (Core 2 E6600 vs. whatever faster Core 2 the OP has, 4GB DDR2 RAM (Can't remember the speed), GeForce 8800GTS 640MB) and could run Doom 3 without a hitch on the same settings.

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TheDarkArchon said:

Sorry, but my old computer was worse than the OP's (Core 2 E6600 vs. whatever faster Core 2 the OP has, 4GB DDR2 RAM (Can't remember the speed), GeForce 8800GTS 640MB) and could run Doom 3 without a hitch on the same settings.


And this is where my concern stemmed from. I distinctly remember maxing this game out on older hardware in the past, without FPS drops. Then I see these gameplay vid's on youtube where people are running SikkModd with AA on worse hardware, without FPS drops (while FRAPsing).

I'll take the driver recommendation into consideration. I've been holding off on the latest WHQL's cause of poor feedback over at guru3d and nvidia forums. I'll probably update with the next release.

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How do other games run? If it's a universal problem and not restricted to Doom 3 then your card isn't doing what it ought to be able to do and it may indicate a defect of some kind. For reference.

Just grab a demo of one of the games listed in that review and see how it runs if you don't have a copy of anything else to hand. Prepare to consider a few FPS difference when you take into account your older CPU, but the difference should be pretty marginal.

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I can run Source engine games (CS:S, DOD:S, L4D2) and Modern Warfare 2 in 1080p, 4x AA/16x AF, rest of in-game settings maxed and maintain 60+ FPS. This is in 50+ player servers, heavy action/lots of smoke, zombie swarms.

With Quake 4, I can do 4x AA in multiplayer and not get FPS drops. Single player is more demanding so I have to bump it down to 2x. Even with 2x, my FPS dips occasionaly during some scenes.

If anybody wants to see an example of the FPS drops I'm getting, fire up Doom 3 with 4x AA or higher and pick any level. Turn on god mode, set com_showfps 1, woop out the rocket launcher and stand facing a wall directly. Now, start spamming the rockets at the ground. Does your FPS dip?

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- GeForce 8800GTS -
Core clock: 650 MHz
Peak fill rate: 10.4B pixels/second
624 GFLOPS

- Geforce 550 GTX Ti -
Core clock: 900 MHz
Peak fill rate: 21.6B pixels/second
691.2 GFLOPS

As you can see, it's not a very impressive step up after seven generations of video cards. Half of the advantage of newer cards is supporting newer shader models and rendering APIs. It's quite possible that Doom's old API calls don't allow for any optimization, and you're relying solely on your card's horsepower. That would explain performance comparable to a dinky old second-rate card.

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Wrong 8800 GTS there. Mine was a first generation one with the core clock at 500MHz, Peak fill rate of 10 billion pixels/second and a maximum shader processing rate of 403.2 Gigaflops.

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