From our experiences playing at 2560x1600 on the Dell 3007WFP 30” LCD with two BFGTech GeForce 8800 GTXs in SLI we can definitely see a trend. Quite simply the AMD Athlon 64 FX-62 is bottlenecking the 8800 GTX SLI to varying degrees. In Flight Simulator X and Medieval II: Total War we find it bottlenecking SLI to a very high degree. The Intel Core 2 Duo X6800 allowed us to obtain “free” 8X AA on the BFGTech GeForce 8800 GTX SLI in Flight Simulator X and also run at the “Medium High” scenery setting. With the AMD Athlon 64 FX-62 we had to lower the AA setting to 2X AA and reduce the scenery settings.
In Medieval II: Total War we experienced a smoother gameplay experience with the Intel Core 2 Duo X6800, especially with thousands of characters onscreen at the same time. With the AMD Athlon 64 FX-62 we had to reduce the character detail as well as the antialiasing setting. These two games were by far the largest differences we saw between both platforms. They greatly demonstrate how SLI needs a fast CPU to feed it at high resolutions.
We also saw a distinct performance difference in Oblivion. However, it was not enough to impact our visual quality settings. The gameplay experience was “smoother” on the Intel Core 2 Duo X6800 and the framerates did not drop down as low, but the game was still playable on the AMD Athlon 64 FX-62. It is very impressive to see Oblivion at 2560x1600 with 2X AA and HDR with maximum in-game settings; this really shows the power that 8800 GTX SLI can provide in games.
Battlefield 2142 also showed us a distinct performance difference, but the framerates were so high that it didn’t matter. We were consistently experiencing framerates above 60 FPS with the AMD Athlon 64 FX-62 at 2048x1536 with 16X TR SSAA. That is quite incredible; 16X TR SSAA at 2048x1536 and above 60 FPS! F.E.A.R. Extraction Point, Need for Speed Carbon and World of Warcraft showed us smaller differences that simply translated to no true differences in-game.
Do we need more graphics memory?
In this evaluation, especially under Oblivion and some other games, we talked about some odd performance experiences. We said that at certain very high settings we experienced a “choppy” or “laggy” feeling in the game even though the framerate indicated playable framerates. It may be that the games are able to render fast enough with 8800 GTX SLI but it may not be able to dump that information to video card memory fast enough, or, it may be running out of framebuffer space on the video card. Could it be that 768 MB of RAM on the video card is simply not enough for certain settings like 2560x1600 4X AA in Oblivion or motion blur being enabled in Need for Speed Carbon?
It may very well not be enough considering how much demand is on the memory at those settings. Perhaps 1 GB or more of graphics memory on video cards doesn’t sound so unorthodox now. Certainly it may not benefit single-GPU video cards as much right now, but with two 8800 GTXs in SLI running at 2560x1600 1 GB or more of graphics card RAM per video card, with more memory bandwidth may just be the ticket for letting the 8800 GTX GPU in SLI really shine. We saw the framerates it can render, but we just can’t play at those levels yet with the current bottlenecks, whatever they may be.
Source:Real-World Gaming CPU Comparison with 8800 GTX SLI