HD3870 Crossfire Scaling: P35 vs X38

Overall Score

In conclusion Crossfire performance on the P35 board was a mixed bag. In some games such as Crysis and Oblivion which were heavily GPU-limited, the reduced bandwidth proved to be insignificant from a performance standpoint. On the other hand the performance hit in UT3 was much more noticeable, and the performance in CoD4 with the P35 board was downright embarrassing. Furthermore, the synthetic benchmark performance on the P35 board also showed a fairly substantial performance hit making Crossfire on the P35 chipset particularly unappealing to benchmarkers.

For people who have X38 boards and want to run Crossfire, the performance testing showed it to be a very effective way of improving performance. For people with P35 boards, the only way two HD 3870s in Crossfire would really be recommended is if you already own one HD3870 and want a way to add performance in GPU-challenging games like Crysis or Oblivion. Otherwise, we would recommend instead of two HD 3870s that these users consider a more powerful single graphics card such as an HD 3870X2 which provides Crossfire-level performance on a single card. Considering that the price difference between a P35 board and an X38 board is greater than the price difference between two HD 3870s compared to a single HD 3870X2, the combination of a P35 and an HD 3870X2 looks more appealing for new system builds unless Crossfire performance in the future is important.

Although the drivers do not yet exist to enable it, the belief is that the X38 chipset boards will have the bandwidth needed to support two HD 3870X2 boards in Crossfire, but this configuration will be completely choked on a P35 (or P965) board using only an x4 link for the second graphics card.

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