Can more CPU power help when GPU is at 100%?

[01zzf8x]

I keep hearing people say that a CPU upgrade can result in more FPS even if the GPU was at 100% load to begin with. This doesn't make any sense to me logically.

If an engine is rendering frames with a 100% load GPU, and the CPU cores are not at full load, that would mean that there is nothing more CPU power could help the engine with.

Can someone give a technical example of how a common game engine could render more FPS with a CPU upgrade if the GPU was at 100% load to begin with (and no maxed CPU cores)?

 

[Rifter]

with no maxed CPU cores i dont see how it would be possible either.

 

[poofyhairguy]

Can someone give a technical example of how a common game engine could render more FPS with a CPU upgrade if the GPU was at 100% load to begin with (and no maxed CPU cores)?

Part of that CPU load is for loading the driver for the GPU. AMD cards in particular have a pretty high CPU load for their drivers.

More CPU power means more CPU cycles for the driver with means the GPU gets fed better and the FPS can go up. Can being the key word.

 

[Flapdrol1337]

if the gpu is at 100% load all the time when gaming it probably won't help much.

 

[01zzf8x]

Part of that CPU load is for loading the driver for the GPU. AMD cards in particular have a pretty high CPU load for their drivers.

More CPU power means more CPU cycles for the driver with means the GPU gets fed better and the FPS can go up. Can being the key word.

If the CPU isn't maxed out, surely there is no more GPU feeding to be done?

Or are you talking about some kind of CPU-latency that isn't affected by workload?

 

[Rifter]

Part of that CPU load is for loading the driver for the GPU. AMD cards in particular have a pretty high CPU load for their drivers.

More CPU power means more CPU cycles for the driver with means the GPU gets fed better and the FPS can go up. Can being the key word.

Would this not only be true if the CPU core doing this was maxed out, because if its not i dont see how having a faster one would help.

 

[Dygaza]

You can get small boost, but not big. 100% gpu usage as a value ain't really accurate either.. Faster cpu can feed gpu faster when it's ready to handle more data, even the difference is marginal.

 

[Bacon1]

Remember even having under 100% core usage doesn't mean that you aren't CPU bound. The CPU just isn't getting the work done fast enough before it has to do other stuff to get the next section of game code for the next update.

 

[frozentundra123456]

Remember even having under 100% core usage doesn't mean that you aren't CPU bound. The CPU just isn't getting the work done fast enough before it has to do other stuff to get the next section of game code for the next update.

That is true, but in that case you would not be using 100%gpu would you?

 

[.vodka]

A while ago I had a C2D e7200 @ 3.8GHz and a new, fresh out of the box 6850 @ 6870 clocks. While playing Assassin's Creed II the 6850 would show 98-100% GPU usage. Great, yet frametimes were all over the place and framerates weren't that impressive. Maxed out I'd see 30-40FPS in crowded areas. 4850 to 6850 maybe wasn't such a good idea... Should've bought a 6950, right? Maybe I'd get lucky and it'd unlock to a 6970, too.

Well, time passed and I upgraded to my current 2500k, five years ago. Stock 2500k, OC'd 6850... FPS shot up well over 55-60 FPS in crowded areas, and frametimes were now buttery smooth. GPU usage in GPU-z was still 98-100%.

So yeah, definitely, there's a case for GPU load to be maxed out yet still be CPU bound, all at the same time. If you think about it, there are different kind of loads that make the usage counter hit 100%... there's games, and there's mining or Furmark for example. A web browser and Linpack. Different kinds of "100%".

 

[Magee_MC]

I keep hearing people say that a CPU upgrade can result in more FPS even if the GPU was at 100% load to begin with. This doesn't make any sense to me logically.

If an engine is rendering frames with a 100% load GPU, and the CPU cores are not at full load, that would mean that there is nothing more CPU power could help the engine with.

Can someone give a technical example of how a common game engine could render more FPS with a CPU upgrade if the GPU was at 100% load to begin with (and no maxed CPU cores)?

I think that before this question can be approached, you have to determine what you mean by 100% GPU utilization.

 

[bystander36]

While there might be some rare exceptions, with small improvements, if the GPU never drops below 100% usage, a faster CPU will not help your FPS.

 

[richaron]

Sometimes more CPU can help, certainly with modern compute implimentaions but this would be rare.

It also depends on what's considered 100% usage. Back to car analogies: If we consider the GPU to be a highway with multiple lanes (aka data paths), a single lane could be packed & it's in a sense running "100%" (aka as fast as possible under this workload). Depending on the software more CPU power could in theory slot more "cars" into the empty spaces in other "lanes". But again I'd say this is unlikely since in this situation the software has already proven itself inneficient.

 

[chummy]

With AMD card thats possible in DX11 CPU bound cases since AMD GPU load reader apparently works in strange ways. What i mean is than even when AMD GPU load showing at 100% usage in some rare cases that dont mean the GPU is really at 100% because with faster CPU is possible to extract some extra performance in specific scenarios. With NVIDIA GPU i find no such "feature". Tested in GTA 5 and in some parts the faster CPU give some 5-15% boost over the weaker CPU while AMD GPU was 100% in both.

In DX12 is very unlikely to find something like that with AMD GPU, only happens in DX11 and probably OpenGL because their infamous CPU driver overhead.

 

[Bacon1]

Also remember that GPU load from afterburner and such aren't 100% accurate. They are best guesses. AMD, Nvidia, and developers all use tools to show frame by frame rendering and what exactly the gpu is doing and how it is loaded.

AMD's GPU PerfStudio, Nvidia's NSight and PIX are examples of the software used, plus whatever they have in engine.

 

[Dygaza]

Also remember in afterburner'ss or gpu-z's case default polling rate is very slow to catch small variations in gpu load. Set polling rate to 0.1s (100ms) and you start seeing those fast dips under 100% way more often. 1s simply is too slow, heck even fastest 100ms is still too slow if we would really want detailed accurate profile.

Also when it comes to threads maximising one cpu core completely (25% in I5 case or 12.5% I7 case), it's very rare to see this happening even when you are cpu bound. Most of the time you have 2 heavy threads running for game. One being the main game logic thread, and otherone being driver thread. Neither of these threads can truly max one cpu core to their theoritical maximum as they have dependancies to other threads (They need to wait for them to finish their calculations before they can continue to their job).

In AMD driver case typically you start getting performance drops when AMD driver uses roughly 10%+ (12.5% theoritical). of I7's performance. After that you mostlike have gpu usage drops as the thread simply can't run fast enough. Main game logic's optimal performance cap kinda varies between games.