Call of Duty 4: Modern Warfare
We tested Call of Duty 4 by recording a custom demo of a multiplayer gaming session and playing it back using the game's timedemo capability. We cranked the in-game detail levels, including texture filtering, and set antialiasing to 4X.

Our Call of Duty 4 test teases out a tangible difference in performance depending on graphics memory size, but it's not between configurations with 512MB and 1GB. Instead, it's the 256MB configuration running behind the curve. At a relatively modest 1280x1024, the 256MB card lags behind by a little more than 10 frames per second. That gap only grows as we crank the resolution, with the 256MB card dropping well below a playable frame rate threshold at 1920x1440.

There's essentially no difference in performance between our 512MB and 1GB cards here, even when they're paired in SLI. As one might expect, overall performance drops as we scale the resolution up, but it does so at a slower rate than with the 256MB card.

Crysis
Crysis is easily the most demanding PC game on the market, and we were able to get reasonably playable frame rates with the game's high-quality detail settings. We started at a relatively modest 1024x768 display resolution without antialiasing and scaled up from there. The scores below come from a custom timedemo recorded in the game's first level.

Again, 256MB of memory proves to be a clear handicap for the GeForce 8800 GT. Even at 1024x768, you're looking at a significant drop in performance. Things only get worse as the resolution goes up.

Between our single-card 512MB and 1GB configurations, we see no meaningful difference in performance up to 1600x1200. At that resolution, we're under 25 frames per second, which is a little choppy to be considered playable, at least for a first-person shooter.

Our SLI configurations provide a little more drama as the 1GB cards inexplicably deliver lower frame rates than their 512MB counterparts at 1280x1024. We re-ran the tests numerous times and after multiple reboots, but got the same results. Things return to normal at 1600x1200, where only one frame per second separates our 512MB and 1GB SLI configurations, with the latter holding the slight lead.