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ShawMishrak

[.net] Xbox - Floating Point Performance

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Has anyone else experienced exceptionally slow floating-point performance on Xbox with XNA? I was trying to run some of my physics code on Xbox for the first time, and found the performance to be poor, to say the least (>60 FPS on Windows to 0.5 FPS on Xbox). To take the garbage collector overhead out of the equation (since I know there are problems with my code there), I tried running a benchmark of 10 mil. matrix multiplies (XNA matrices) on Windows and Xbox, and I was getting over a 50% performance drop on Xbox, compared to my three year-old P4 3.0GHz desktop with a DVD movie playing in the background. I used the 'ref/out' version of the matrix multiply routine to prevent excessive copying on the Compact Framework. I know that the Compact Framework on Xbox is still fairly unoptimized for floating-point operations and that it does not take advantage of Altivec yet, but I'm still surprised that the performance drop is so severe. Even a custom written matrix multiplication routine on XNA matrices (to take out the possibility of XNA on Windows using SSE) on my P4 runs significantly faster than the same code on Xbox. Is this a common problem, or am I probably missing something here? Thanks.

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