I've heard a lot of times that if you lower your game settings (for any game) or resolution, it takes the load from the GPU and gives it to the CPU. How exactly does this work and why?
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Re: Lower settings = more CPU load?
Ok, when you design a system, you try to eliminate all the bottlenecks. Right? Bottlenecks limit performance because one component is being stressed while others remain idle.
Now in every system, even custom built ones, bottlenecks exist. It is impossible to build a bottleneck-free system. BUT the bottlenecks in well designed systems are so tiny that they are realatively insignificant. This happens when the GPU is running 100% max but the CPU is only at 90%. Technically speaking the GPU is the bottleneck. The CPU has remaining power not being used because it's waiting on the GPU. But this is an extremely minor case and has little effect on performance.
Now, to answer your question. Let's take the situation above. GPU=100%, CPU=90%. Currently the GPU is the bottleneck. CPU processes the data and sends it to the GPU to be rendered and displayed. When you turn down the settings on a game, the FPS increaces right? Why? Easy, the GPU is doing less work. Now the GPU is not at 100% utilization anymore. BUT, there are more frames that need to be sent to get displayed by the CPU. The CPU now has an increased load. Yes the GPU is displaying more FPS, but they are simple to do. Let me make an example.
Take two people. One creates math problems, the other solves them. (CPU creates, GPU solves) GPU bottleneck is when the creator makes hard problems. The creator is sitting there while the solver works. When you turn the game settings down, you turn down the difficulty of the problems. Now the creator is working hard to give enough addition problems to the solver. Meanwhile, the solver is breezing through the problems. Yes there are more problems, but they're easy. The stress is on the creator.
You see? When the settings are turned down, the GPU has less to render but the CPU has more to give. When the CPU reaches 100% while the GPU isn't 100%, then the game is CPU-Bound. The rate at which the CPU can deliver data for the GPU to render determines performance. The game is GPU-Bound when the rate at which the GPU can render data determines a game's performance.
Make sense? I can clarify or answer questions if needed. -
Re: Lower settings = more CPU load?
Pretty much what Spark said. If you lower the graphics settings, the thing left for the computer to do is the calculations (rocket movement, player movement, bullet movement, who got shot, who shot it etc).
The CPU does all that. So the GPU moves far ahead of the CPU as it has pretty much nothing to do. That's why there are minimum requirements (which ends up CPU intesive), and recommended which is the balanced load.Comment
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Re: Lower settings = more CPU load?
wow that was a great way to explain it sparkComment
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Re: Lower settings = more CPU load?
So the GPU is pretty much working at a speed in which the CPU can't keep up or vice versa?
Great explanation.Comment
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Re: Lower settings = more CPU load?
Yup..Comment
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Re: Lower settings = more CPU load?
So it's better to have a fast CPU and a slower GPU than the opposite
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Re: Lower settings = more CPU load?
It depends on the game. Some are CPU bound and others are GPU bound. But generally the game is GPU bound.Originally posted by Sam1990 View Post
Same as above, most games are GPU bound so it would be better to have a faster GPU. Tom's hardware had an article about different CPU+GPU combinations. The cheapest FPS was achieved with a Pentium Dual Core and a 8800GT. Generally, the GPU is betterOriginally posted by IquereComment
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Re: Lower settings = more CPU load?
This depends quite alot on the game though, which is why when I first bought my computer it was initially just for FSX more or less, which is very very CPU bound. And which is why I spent less on GPU (7600GT) than on CPU (E6600).
However, this works like a charm in most games, I do notice the GP as a bit of a bottleneck, but I get good frames in most of the games I play.Comment
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Re: Lower settings = more CPU load?
So is performance actually worse in terms of FPS, or is the CPU load just higher? Would enabling a framerate cap help?Comment
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Re: Lower settings = more CPU load?
Originally posted by Wizrdwarts View Post
Whadda mean?
Are you asking "if you turn the settings down will you get a performance decrease?" The answer to that is no because your FPS will go up because the GPU has less to do.Comment
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Re: Lower settings = more CPU load?
CPU load only goes up. As Spark said, the GGPU has less to do, so the FPS WILL have to go up.Comment
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Re: Lower settings = more CPU load?
So your FPS won't go down, CPU load will just go up?Comment
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Re: Lower settings = more CPU load?
But if the CPU load goes too high and reaches 100% usage, it will cut your FPS by a big amount...Comment
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Re: Lower settings = more CPU load?
I get it now, thanks. :)
Which explains why 2 GTX 280s actually do worse in Quake Wars compared to one GTX 280.Comment
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