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Old 03-16-05, 05:51 AM   #3
ChrisRay
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Join Date: Mar 2003
Location: Tulsa
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Default Re: Nvidia 6800GT SLI investigation




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Benching Methodology: All benchmarks were done with fraps. I took 3 preset runs through a specific area of each map and divided the results by 3 to take the average. Average results were usually within 1 FPS. I feel these real time results are more accurate than time demos because they take into account in all game factors.




Half Life 2 was to be this years poster child DirectX 9.0 game. The game features a plethora of DirectX 9.0 shaders running in full FP32 precision on Nvidia hardware. Despite all this there are many situations where Half Life 2 appears to be CPU limited. Under many circumstances I found the minimum frame rate to be rather constant in this map. Otherwise SLI does seem to be doing its job. In Situations where 8xAA is used you see almost double performance.



Nvidia Custom AFR profile





As Half Life 2 is the poster child DirectX engine. Doom 3 is the poster child OpenGL engine for this last year. Most notably is the graphic engine seems to be completely limited by your graphic setup at these resolutions and scales accordingly. The game was completely playable @ 4xAA/16xAF with 1600x1200 resolution. To me this is quite a feat because even on a single 6800GT I have had to settle for less than that due to the game becoming choppy occasionally. The 8xAA solutions werent really playable with SLI with the exception of 1280x1024 resolution. However one thing really stands out. SLI is the way Doom 3 is meant to be played.


Profile: Standard AFR Profile




Far Cry was one of the first real tangible DirectX 9.0 games released. Offering stunning lighting and visuals and impressive wide open areas. The graphics were known for bringing last year and this years hardware to its knees. SLI scales fairly well with Far Cry. In most cases providing a pretty tangible increase. I was able to play Far Cry perfectly acceptably @ 1600x1200 with 4xAA/16xAF with no slow down. However 8xAA did not scale as well as we have seen in the prior games. This is probably due to the fact that the game uses SFR for its multi gpu rendering method. SFR usually does not scale as well as AFR unfortunately.


Profile: Nvidia Custom SFR Profile




Call of Duty is one of our tests that is not originally enabled for SLI by default. I had to coax it and edit out the single GPU rendering profile within the nvapps.xml. Then I enabled AFR through the control panel. This game is strongly CPU limited on an SLI setup. Even CPU limited @ 4xAA/16xAF at 1600x1200 resolution.. However turning up 8xAA/16xAF really allowed the SLI setup to stretch its legs. Call of Duty played at 8xAA/16xAF @ 1600x1200 resolution with smooth frame rates really is a site to behold.




Profile: Forced AFR profile




Admittedly this was my first chance to play Halo when doing this review. The game seems to feature a great deal of pixel shader 2.0 effects for speculiar effects among other things. The game does not seem to support anti aliasing so I left them disabled during this benchmark. In its stead I decided to use HQ anisotropic filtering for maximum quality in game. SLI once again scaled extremely well and brought many modes that were unplayable with a single GPU to a completely playable and enjoyable experience.


Profile: Nvidia Custom AFR Profile




I designed the Neverwinter Nights Harrowdale module. Back in the Geforce 4 days this game was very demanding on graphic cards and cpus alike.. I created the demo to use high amounts of fog and water effects rendered with pixel shaders. However like many other engines as time has passed its become an extremely CPU limited game that has not scaled well at all.. I know you're probably thinking. "Why bother benching this game?". The answer is pretty simple. If you have an SLI setup and are finding yourself CPU limited. You might as well crank it up.


Profile: Forced SFR Profile




Unfortunately this game didnt seem to scale well with SLI at all. Much to my surprise SLI provided minimal benefit to 8xAA. This could be seen by the fact that when you turned on 8xAA the load balancer fell to the bottom of the screen which means the secondary graphic card was doing very little. This didnt happen with the 4xAA tests. I speculate that 8xAA has become completely bandwith limited and SLI doesnt seem to scale as well with bandwith limited situations compared to situations which are fillrate limited. I have also noticed this oddity in Unreal Tournament games.

Profile: Custom SFR Profile




Conclusion: Well What can be said? SLI has come along way since I did my original article and that was only a month and a half ago! With Coolbits 2.0 you are able to manually set your own profiles within the Nvidia control panel as well globally force SLI. These are all steps in the right directions from the time I made my previous article.

What else can be said? Two Geforce 6800GTS operating in SLI mode provide ample performance with some to spare. I am happily going to be gaming on this rig for sometime to come. There are a few odd circumstances where SLI can fail such as games utilizing render to texture effects such as motion blur or bandwith limited games which are not limited by the GPUS graphic engine. However those issues aside. SLI has scaled exceedingly well and IMO there is no current better Dream Machine than a high end Nvidia SLI rig.
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Last edited by ChrisRay; 03-17-05 at 01:18 AM.
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