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How do i know when im bottle necked again

post #1 of 3
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when im 100% gpu, less than 100 cpu

or 100 cpu less than 100 gpu
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post #2 of 3
Being at <99% GPU usage suggests that SOME TYPE of bottleneck is happening with your framerate. CPU is a likely candidate, but by no means the only possibility. This can be caused by LOTS of things, including drivers, PCI-Ex bandwidth, even a bottleneck within the card itself, such as your card not having enough vram or memory bandwidth for the task at hand, too slow a texture fillrate, excessive texture swapping, etc.

Being at 99% gpu usage strongly suggests that you have no bottlenecks occurring on your framerate (at least, none that you could possibly do anything about).

Being at 100% (total across all cores) CPU usage means that there's a good chance you are getting some CPU bottlenecking on your framerate, but it's not possible to tell how much. Could be a big bottleneck, could be a small one.

Being at <100% CPU usage provides virtually no valuable information whatsoever re: whether or not you're cpu BN'd, unless you have a single-core chip, in which case it most probably means you are not. Although if you have a dualie, and it's at <100% chances are pretty good that you're not CPU BN'd, too, because most modern games can at least fully use two cores.

The PROPER method to check for CPU-bottlenecking is to run a benchmark at CPU clock X, then increase the CPU clock by Y% up to clock Z, then run the same test again. Observe the % change in FPS that occurs as a result, and divide the % change in FPS by the % change in CPU clock. The closer this ratio is to 1, the more CPU-bottlenecked you are AT CLOCK X.

However, bear in mind that all you're determining is the amount of CPU bottleneck on THAT test (i.e. game or benchmark), at the settings you ran it at (although it's safe to assume that higher IQ settings would exhibit less bottlenecking). The importnat thing to understand is that every test is going to be different, because different games/benches vary dramatically in terms of the amount of CPU work required per frame rendered.
Edited by brettjv - 7/21/11 at 11:06am
    
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post #3 of 3
Graphical representation of what brettjv has said above (5th paragraph):-

When there is a slope, there is a CPU bottleneck. The steeper the slope of the graph is, the larger the bottleneck.

When the slope of the graph is zero or almost zero, then the CPU is not bottlenecking.

For the example graph below, when the CPU is above 2.5GHz, there is practically no CPU bottleneck (for this game at this resolution and details).
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