How do I detect an FSB bottleneck

[milindsmart]

I am running Darksiders on a Q6600 + Radeon HD 6850 with MSI P45 platinum. At certain situations I get only 15-20 fps. The funny thing is, neither the CPU(62%) nor GPU(60%) was running at full load. So I now suspect FSB to be the bottleneck.

But how do I test it? I am pretty sure that it's not number-of-cores limited, because it would be 50% or 25% then, not 62%, if so. Any better way to check?

 

[elemein]

Easy. Underclock or overclock the FSB and see if it affects the performance greatly in the game.

 

[milindsmart]

I tried that. For darksiders it seems to have increased the max FPS. But not the minimum... there are still locations where framerate is around 20.

The game Witcher (1) is even more peculiar. The place I tested (Act 4: Lakeside) gives me a min of 25 fps, standing still(!) at one particular location looking at both sky and ground covered by plants. This minimum has not changed with increasing clock speed.

CPU 1 core 100%, GPU 20-30%, VRAM 30%, HDD activity low.

The CPU utilization has not changed despite change in frequency. Yet min FPS hasn't changed here too. Max FPS I'm not bothered about.

 

[smeezekitty]

Sometimes my Core 2 Duo does the same thing. I think it is a CPU bottleneck.

A significant OC should fix it.

 

[elemein]

I tried that. For darksiders it seems to have increased the max FPS. But not the minimum... there are still locations where framerate is around 20.

The game Witcher (1) is even more peculiar. The place I tested (Act 4: Lakeside) gives me a min of 25 fps, standing still(!) at one particular location looking at both sky and ground covered by plants. This minimum has not changed with increasing clock speed.

CPU 1 core 100%, GPU 20-30%, VRAM 30%, HDD activity low.

The CPU utilization has not changed despite change in frequency. Yet min FPS hasn't changed here too. Max FPS I'm not bothered about.

You have a FSB bottleneck.

FSB bandwidths are limited by bandwidth. Max frames = max bandwidth.

Your bottleneck would not come in a situation where there would not be a max bandwidth (minimum frames). So your maximum frames are bottlenecked by your FSB, but your minimum is held back by your CPU or GPU.