hething

Hi all,

I'm still a bit confused about this bottleneck-thing? I recently bought 3x eVGA GTX470SC's and they are now SLI'ed on my eVGA 790i ULTRA SLI motherboard. My CPU is the Intel Q9650 3000mhz at Stock, but overclocked to 4275mhz. 
On this forum a lot of people are asking if their CPU/GPU are bottlenecking the other, but how can u guys know which is the bottlenecking-part? How can I find the bottleneck on my system?

      // Hething / =EGC=KiLLingQ

• 1) Adding the 2nd, 3rd card results in little/no performance gain, poor SLI scaling at your resolution, benchmarks are all off what you're expecting.
• 2) GPU usage in AfterBurner/Precision, if this % is low your GPUs are not working very hard.  If load on each GPU is 33% or less with 3 cards that's going to roughly be the equivalent of 1xGPU, if 50% or less with 2 cards thats going tob e roughly the equivalent of 1xGPU at 100%.
• 3) If you increase GPU intensive settings, like AA or resolution, and you don't see any drop in FPS.  You basically get it for "free", because the GPUs can't work harder in producing more FPS, but they can use those extra GPU cycles to handle that same frame at a higher resolution or with lots more AA or advanced shader effects.  Nvidia Surround is also a good way to increase resolution nowadays instead of the previous expensive option of 2560x1600.
• 4) Decreasing resolution and settings do not yield more FPS.  This means reducing load further on the cards still does not increase FPS because again, the CPU/game engine is already taxed and can't provide more frames to be rendered.
• 5) Overclocking/Underclocking your CPU and running/monitoring repeatable benchmark runs to see how much difference there is in performance.  Typically people who overclock will already have overclocked to the max, so it is difficult for them to determine what happens if you add a faster CPU, but it is much easier to downclock their CPU to see what kind of impact that has on performance.  Even in very CPU demanding titles, you typically will not see linear increases in FPS with CPU speed increases, but there are some that will.  You can also keep an eye on CPU usage in Task Manager or Performance Monitor.  If any single core hits 100% consistently, you may be CPU bottlenecked.
• 6) Overclocking/Underclocking your GPU and and running/monitoring repeatable benchmark runs to see how much difference there is in performance.  If you are not CPU limited, then you should see a near-linear increase in performance with GPU clockspeed increases.  Similarly, underclocking would as well, unless you're CPU limited, in which case underclocking wouldn't result in much drop off at all.