Will a bad GPU bottleneck a high end CPU?

[Carlos1010]

Hi all,

Just curious because i've always heard that a CPU can overclock a GPU but I have no clue if this is possible, can a GPU bottleneck a CPU? Thanks in advanced! 

[byalexandr]

Yes but usually in games this doesn't matter.

[79wjd]

Technically even a high end GPU (GTX 1080) will bottleneck a high end CPU (6700k) in most current games. 

[agent_x007]

Depends what you do with "high end CPU"
Crunching PI or other number - Nah.
Watching YT - Probably not...
Playing pinball/saper - Nope.
Plaing Crysis - Probably/Yes

@up Again : Depends on graphics level and game itself - I'm pretty sure at HD Ready + Medium settings i7 will not keep up with GTX 1080.

[Shubham Yadav]

3 minutes ago, Carlos1010 said:

Hi all,

Just curious because i've always heard that a CPU can overclock a GPU but I have no clue if this is possible, can a GPU bottleneck a CPU? Thanks in advanced! 

There will always be a bottleneck. Imagine the components as a production ramp in a factory. If one of them is slower than others to do it's task, the others will have to wait around for him to finish so that next one can begin getting produced. 

 

The only case where you won't have a bottleneck will be if the task is such that both work perfectly in sync and equal to each other. In that case, the CPU won't have to wait for GPU to render and the GPU won't have to wait for CPU to process or compute something. Make any one of them slightly faster and the other one becomes the bottleneck. 

 

If both are too fast, then your monitor refresh rate becomes the bottleneck. 

[typographie]

20 minutes ago, Carlos1010 said:

Hi all,

Just curious because i've always heard that a CPU can overclock a GPU but I have no clue if this is possible, can a GPU bottleneck a CPU? Thanks in advanced! 

A "GPU bottleneck" is what you have if you have successfully avoided a platform (CPU/memory) bottleneck. If your framerate is uncapped, you have either one or the other. To put this another way, basically what you want is a CPU fast enough to stay out of your GPU's way.

 

GPU-bound performance is usually preferable because you can then adjust your in-game graphics options to tweak performance. In a game that's truly CPU-bound, changing resolution or graphics options usually does not affect your framerate much. That's actually one of the ways to diagnose a CPU bottleneck: set your resolution to 800x600 and see if performance improves. If not, it's your CPU.

[KakenBetaal]

23 minutes ago, Shubham Yadav said:

There will always be a bottleneck. Imagine the components as a production ramp in a factory. If one of them is slower than others to do it's task, the others will have to wait around for him to finish so that next one can begin getting produced. 

 

The only case where you won't have a bottleneck will be if the task is such that both work perfectly in sync and equal to each other. In that case, the CPU won't have to wait for GPU to render and the GPU won't have to wait for CPU to process or compute something. Make any one of them slightly faster and the other one becomes the bottleneck. 

 

If both are too fast, then your monitor refresh rate becomes the bottleneck. 

Great description, well put. btw my monitor is an Asus PG279Q. It's not the bottleneck in my system.

[Shubham Yadav]

Just now, KakenBetaal said:

Great description, well put. btw my monitor is an Asus PG279Q. It's not the bottleneck in my system.

Play minecraft. Now it is. 

[KakenBetaal]

LOL! Minecraft is not installed on my system. In fact I know very little about the game. /me goes off to look up what systems run minecraft well.

[SpaceGhostC2C]

3 hours ago, Shubham Yadav said:

There will always be a bottleneck. Imagine the components as a production ramp in a factory. If one of them is slower than others to do it's task, the others will have to wait around for him to finish so that next one can begin getting produced. 

 

The only case where you won't have a bottleneck will be if the task is such that both work perfectly in sync and equal to each other. In that case, the CPU won't have to wait for GPU to render and the GPU won't have to wait for CPU to process or compute something. Make any one of them slightly faster and the other one becomes the bottleneck. 

 

If both are too fast, then your monitor refresh rate becomes the bottleneck. 

As "bottlenecks" are task-specif (it is the task that faces a bottleneck due to one part working slower than the other), what you say is 100% true as long as we are talking about a very specific task: maximizing FPS. For a Guinness record or for the sake of it.

 

Nowadays many people look very seriously into FPS maximization for unexplained reasons, or perhaps as a byproduct  of benchmarks. In benchmarks, it makes sense to look at unbounded FPS because you need an unbounded measure of performance. It doesn't matter if there is a useful application for said performance, you still want to measure it. It's like high wattage PSUs: you will hardly need them, but you can still test them and measure whether they deliver the promised wattage or not, and how much they can deliver, etc.

 

However, back in the consumers' desks, what really matters is the presence of bottlenecks in their actual tasks. "Gaming" is an ill-defined task: it depends on which game, and especially depends on the visual output you expect to obtain. "I want to run Doom in 1920x1080 at 144FPS" is a much better defined task that we can evaluate. There is no reason why the task should be to maximize FPS, or resolution (you could also say your monitor is "bottlenecking" the rest because it's only 4k, while the rest of your set up could handle 2billion x 1.2 billion at 60FPS), and while it is also valid (hey, who am I to judge?), I believe most users would care about their systems doing something they can actually perceive (maybe they won't really enjoy 1000 FPS(*) that much). Maybe the monitor is not a bottleneck: it's just exactly what you want it be. You define the task.

 

To use a non-PC example as well: you can measure the maximum speed of a car, and you can find that car A can reach twice the legal speed limit in your state, while car B can reach three times the limit. Additional testing could reveal they have the same aerodynamic properties, concluding that A's engine is "bottlenecking" maximum speed, which would be true -for the test. For consumers driving at the limit, maybe 10% faster for overtaking, there won't necessary be any engine bottleneck to discuss: the task they try to carry out is not maximizing speed, but something else. Or back to the factory example: you can have workers lazing around all along the production line. I guess there's always either a bottleneck somewhere or overkill. I think "overkill" is the word often missing in the "bottleneck" discussions in this forum.

 

Once you put it this way, many times there will be bottlenecks, and many other times there won't by any.

 

 

(*) Please, if anyone has something like Medieval Total War 2 lying around, try installing it and measure your FPS and GPU/CPU usage with vsync off, then tell us your experience  

[Shubham Yadav]

8 hours ago, KakenBetaal said:

LOL! Minecraft is not installed on my system. In fact I know very little about the game. /me goes off to look up what systems run minecraft well.

You will probably run minecraft at above 1000 fps easy. Some people have managed to run it above 5000 fps. 

[KakenBetaal]

Is the monitor then the bottleneck, or is it the human being?