Hyperthreading and bottlenecks.

[dopefishz]

Simple question, could not find an answer on Google.

With an HT CPU, 4 cpu and 8 logical cores, how can you tell if you're GPU is bottlenecked by your CPU.

Does 50% utilisation means bottleneck ?

Or does 100% means bottleneck ?

Thanks a lot.

 

[Yakk]

The answer to that would be ... depends

Depends on the if the CPU level cach(es) are filled up and thereby the threads will never be 100% saturated. Also depends on threading optimization. Threads may be available, but with nothing to do while it waits for an instruction which may be dependent on another operation's result. Really depends on the code taking place. You often hear DX11 mostly depends on 2 cores, because of the limited threading which could mean less than 50% CPU utilization, yet there is your bottleneck. Or you can have a game engine like Dice's Frostbyte engine which can practically max out all 8 threads & 100% GPU(s) utilization by having some very clever coding and scheduling techniques behind it.

Depending on the graphics engine, and API used now, a LOT of CPU time can be completely wasted due to bad coding and/or work scheduling.

 

[primetime]

Well you could also lower the graphics and resolution settings on a game without frame limits and if the fps does not increase.....Its cpu bottle necked . Simplistic but true

 

[buhbuhfet]

one way to tell if you're bottlenecked, find a graphics benchmark that has presets, like unigine heaven(extreme preset), compare your score to other peoples score that have the same video card and much better cpu(using the same preset), if your score/fps is a good bit lower, means you're bottlenecked