CPU limited?

[Modular]

So we've all heard it said before: "You'll be CPU limited with that card" etc.

Can someone please explain what it means to be CPU limited to me? I'm pretty sure I have a basic idea, but I've heard some conflicting views concerning what it means.

Thanks

 

[incompleteunit]

It basically means that the CPU can't feed data to the video card as fast as the card can render it. The GPU is waiting for the CPU.

Since everything needs to be prepared by the CPU before rendering (calculating positions, physics, AI, blah blah), running a game depends on both CPU and GPU power.

So since the CPU is the limiting factor in a case like that, you'll often see similar performance across resolutions, since the data the CPU is processing isn't dependent on resolution.

I think it's been rather rare in the last few years - CPUs are might fast, and the fancy graphics in games have been getting more complex faster than any other part of the game.

 

[Modular]

OK, thanks. What are some ways to test for CPU limitation? If I play at 1024x768 and get the same FPS as when I play at 1680x1050 I am CPU limited correct?

 

[incompleteunit]

That's one sign. Another way would be to look at reviews of your graphics card and check the CPU they used to test it. If their results are significantly better with the same GPU but a faster CPU at the same resolution, then you would probably benefit from a faster CPU (assuming the rest of the system is comparable).

 

[Munky]

Unless you're using an ancient cpu, the cpu limitation is blown way out of proportion. In cases where a cpu is the limiting factor, you're still getting high enough fps that it wouldn't matter. For example, with a A64 and a 8800gtx you might get "only" 110fps in CS:S, as opposed to 130fps with a C2D, so what? On the other hand, when your gpu can't keep up with the rendering load, your fps start to drop into the 40's, 30's, and below.

 

[BFG10K]

If I play at 1024x768 and get the same FPS as when I play at 1680x1050 I am CPU limited correct?

Yes.