HD3870 Crossfire Scaling: P35 vs X38

Overall Score

Call of Duty 4: Modern Warfare

Call of Duty 4 is another first person shooter from Infinity Ward and published by Activision. Like UT3, CoD4 runs quite well even with a single graphics card yet has visually appealing graphics in addition to the high performance. To test performance in CoD4, a manual run through a level was performed at each setting and captured by Fraps. Runs were performed with no filtering and again with 4x Anti-Aliasing (AA) and 16x Anisotropic Filtering (AF) enabled. All other graphical options were set to their maximum settings.

With the X38 system, we see excellent Crossfire scaling in CoD4 with no filtering enabled. Although the framerate was already quite good with a single card, Crossfire made it even better and operated with very high scaling efficiency. To make the GPUs work a little harder, AA and AF were enabled and the runs were repeated:

With AA and AF enabled, the Crossfire scaling using the X38 board looked even better, approaching the elusive 100% efficiency level at 1280×1024 and 1680×1050. With Crossfire enabled, performance of the game was spectacular even at 1680×1050 and 4xAA. Now the question was, how will the P35 board scale on CoD4?

Unfortunately the answer regarding the P35 is that the performance was atrocious in CoD4 with Crossfire enabled. The game was reinstalled, Catalyst 8.1 and 8.2 were both tried, the in-game multi-GPU option was set to both enabled and disabled, but no matter what the performance with Crossfire enabled on the P35 board was worse than with a single card. Both cards were heating up indicating that both were active, 3D Mark was run between CoD4 runs to ensure that Crossfire was operating correctly, but the only conclusion that could be reached was that Crossfire performance for this game was unacceptable using the P35 board. The good news is that the single card performance was still good, but this was still a major setback for the P35’s Crossfire prospects. Next AA and AF were turned on to see if they could reverse the trend.

Enabling AA and AF didn’t change the conclusion – P35 Crossfire perfomance in CoD4 was simply no good.


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