Crysis
I was a little dubious about the GPU benchmark Crytek supplies with Crysis after our experiences with it when testing three-way SLI. The scripted benchmark does a flyover that covers a lot of ground quickly and appears to stream in lots of data in a short period, possibly making it I/O bound—so I decided to see what I could learn by testing with FRAPS instead. I chose to test in the "Recovery" level, early in the game, using our standard FRAPS testing procedure (five sessions of 60 seconds each). The area where I tested included some forest, a village, a roadside, and some water—a good mix of the game's usual environments.

Due to the fact that FRAPS testing is a time-intensive endeavor, I've tested the lower-end graphics cards at 1680x1050 and the higher end cards at 1920x1200, with the G92 SLI and CrossFire X configs included in both groups.

This is one game where additional GPU power is definitely welcome, and the dual 9800 GTX and GX2 configs seem to be off to a good start at 1680x1050. Median lows in the mid-20s in our chosen test area, which seems to be an especially tough case, tend to add up to a pretty playable experience overall.

However, the performance of the three- and four-way G92 SLI configs begins to go wobbly at 1920x1200, where we'd expect them to get relatively stronger. Heck, the three-way 9800 GTX setup has trouble at 1680x1050, even—perhaps a sign that that third PCIe slot's bandwidth is becoming a problem. Now look what happens when we turn up Crysis' quality options to "very high" and enable 4X antialiasing.

Ouch! All of the G92-based configs utterly flounder. The quad SLI rig simply refused to run the game with these settings, and the others were impossibly slow. Why? I believe what's happening here is the G92-based cards are running out of video RAM. The GeForce 8800 Ultra, with its 768MB frame buffer, fares much better. So do the Radeons, quite likely because AMD's doing a better job of memory management.

To be fair, I decided to test the G92-based configs at "very high" with antialiasing disabled, to see how SLI scaling would look without the video memory crunch. Here's what I found.

Even here, three- and four-way SLI aren't appreciably faster than two-way, and heck, quad SLI is still slower. You're really just as well off with two GPUs.

Unreal Tournament 3
We tested UT3 by playing a deathmatch against some bots and recording frame rates during 60-second gameplay sessions using FRAPS. This method has the advantage of duplicating real gameplay, but it comes at the expense of precise repeatability. We believe five sample sessions are sufficient to get reasonably consistent and trustworthy results. In addition to average frame rates, we've included the low frames rates, because those tend to reflect the user experience in performance-critical situations. In order to diminish the effect of outliers, we've reported the median of the five low frame rates we encountered.

Because UT3 doesn't natively support multisampled antialiasing, we tested without AA. Instead, we just cranked up the resolution to 2560x1600 and turned up the game's quality sliders to the max. I also disabled the game's frame rate cap before testing.

I probably shouldn't even have included these results, but I had them, so what the heck. Truth be told, UT3 just doesn't need that much of a graphics card to do its thing, especially since the game doesn't natively support antialiasing. With the median low frame rates at almost 30 FPS on a GeForce 9600 GT, the rest of the results are pretty much academic. In both the Nvidia and AMD camps, the three-way multi-GPU configs consistently outpace the four-way ones here, as we've seen in other games at lower resolutions, when the CPU overhead of managing more GPUs dominates performance.