HD3870 Crossfire Scaling: P35 vs X38

Overall Score


Crysis. This generation of games’ Oblivion – the game that any graphics card available as of its release struggles to run with all the options on. The good news about Crytek’s DX10 shooter is that the minimum acceptable framerate for appearing smooth to the eye is only about 25~30 FPS rather than the 60 FPS most games require. The bad news is that even that can be a challenge to maintain without judicious use of the graphical options. Crysis was tested using the built-in GPU benchmark script and was running with all in-game options set first to medium and then to high.

On the X38 board, Crysis ran very well with medium settings. Next the same test was repeated on the P35 board.

Much like in Oblivion, Crossfire was not helpful at low resolution but was starting to prove its worth by 1680×1050, although with less scaling efficiency than the X38 board offered. To see if an effect similar to turning AA on in Oblivion would occur, Crysis was tested again with all settings on high but without anti-aliasing.

Again, the X38 board showed good but not incredible scaling from one card to two. The hope was that like Oblivion, Crysis would show no penalty for the P35 board’s limited bandwidth as the GPUs became bogged down at higher resolutions with the high detail level.

Once more the hope was borne out – Crysis with high settings again showed no appreciable penalty for the x4 bandwidth to the second slot as the resolution reached 1680×1050.

The charts below summarize the scaling performance under Crysis for both boards. The single card framerate was averaged and combined into a single data point since the single card performance of the cards was similar enough.

In this chart it is interesting to observer the P35’s Crossfire performance deficit with respect to the X38 closing quickly as the resolution increases.


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