Finding the hardware bottleneck

[HeXen]

Does anyone know of any kind of software or something to show how much time is spent in between game logic loops iterations, an how much time is spent inside a pass through of the video pipeline?

to see if CPU or GPU is the bottleneck?



Moved from PC Gaming

Anandtech PC Gaming Moderator
KeithTalent

 

[minmaster]

well for starters, try to see if there are differences when you lower your resolution. if lowering resolution gives nearly the same performance, it's usually the CPU that's bottlenecking.

 

[NoQuarter]

The easiest way to test if you have a GPU bottleneck or CPU bottleneck is to check your fps at your desired settings, then lower the resolution/AA and see if the fps goes up. If it does then your CPU is fine, because it's capable of pushing more FPS than your GPU is handling at the higher settings. If the FPS stays flat then the GPU is your bottleneck because it wasn't hindered by the higher resolution and AA, it just isn't getting enough outta the CPU to go faster.


Some games demand a lot from the CPU, some not much. Unreal Engine games are pretty easy on the CPU, RTS/sandbox/some rpgs are pretty tough on CPU because of the heavy AI, as is BFBC2 (probably cuz of physics calcs)

 

[HeXen]

if lowering resolution gives nearly the same performance, it's usually the CPU that's bottlenecking

lower the resolution/AA and see if the fps goes up. If it does then your CPU is fine
If the FPS stays flat then the GPU is your bottleneck

uhm......

 

[HeXen]

actually, i'd rather just see the time differences. Like if the CPU logics is 11ms and GPU rendering is 1ms...then i know i need to upgrade the CPU

IF difference is CPU is 8ms and GPU is 4ms...then upgrading is not a big deal and i'll be ok with majority of games.

the resolution test thing really tells nothing. cause thats the difference of the engines themselves, they all will behave differently and upgrading either CPU or GPU will only solve the difference of which games are bound to the upgrade...the key is balance...thats why i want the specific details.

just wondered if such a debugging tool exists but apparantly even the resolution test is debatable as to which is which cause 2 different answers is confusings 🙂

 

[Fenixgoon]

uhm......

if you look at anand's reviews, that's exactly how they examine CPU/GPU bottlenecks in games.

hence why a comparison of cpu's is done at extremely low resolutions/details - to eliminate GPU effects (and using the fastest CPU to test GPUs)

 

[HeXen]

if you look at anand's reviews, that's exactly how they examine CPU/GPU bottlenecks in games.

hence why a comparison of cpu's is done at extremely low resolutions/details - to eliminate GPU effects (and using the fastest CPU to test GPUs)

but which answer was correct? thats why i said "uhm"
one says if lowering resolution and the fps is the same, its the gpu, othe says its the cpu? which is it?

 

[minmaster]

if lowering resolution and fps stays same, it means the gpu isn't the problem.

 

[NoQuarter]

if lowering resolution gives nearly the same performance, it's usually the CPU that's bottlenecking

lower the resolution/AA and see if the fps goes up. If it does then your CPU is fine
If the FPS stays flat then the GPU is your bottleneck

uhm......

Resolution and AA are 99% GPU's responsibility, CPU has little to do with those. So when you reduce resolution/AA you are allowing the GPU to pump out frames faster, so FPS should go up if the CPU can supply them.

If the FPS stays flat, that means the CPU can't supply the frames fast enough even though you've made everything as easy as possible on the GPU.

The CPU is responsible for AI, physics and scene setup, and the GPU has nothing to do until the CPU is finished with each of those things for setting up the new frame.

 

[Bman123]

if lowering resolution and fps stays same, it means the gpu isn't the problem.

+1

 

[Sylvanas]

Beyond3D used AMD's GPU Perf Studio to analyse GPU cycles and instruction time within a scene- this is probably the closest to what you may be looking for.

 

[Lonyo]

actually, i'd rather just see the time differences. Like if the CPU logics is 11ms and GPU rendering is 1ms...then i know i need to upgrade the CPU

IF difference is CPU is 8ms and GPU is 4ms...then upgrading is not a big deal and i'll be ok with majority of games.

the resolution test thing really tells nothing. cause thats the difference of the engines themselves, they all will behave differently and upgrading either CPU or GPU will only solve the difference of which games are bound to the upgrade...the key is balance...thats why i want the specific details.

just wondered if such a debugging tool exists but apparantly even the resolution test is debatable as to which is which cause 2 different answers is confusings 🙂

Yes, games differ. That's why there is not necessarily one single bottleneck, it all depends on your system. In one game, you may have a GPU bottleneck, but in another on the same computer you may have a CPU bottleneck.

Obviously it all depends on balance, but ms doing this and ms doing that won't really help you.

 

[HeXen]

Beyond3D used AMD's GPU Perf Studio to analyse GPU cycles and instruction time within a scene- this is probably the closest to what you may be looking for.

thanks a lot. i'll look into this