What is the meaning of a cpu bottlenecking a graphics card?

Question

I have a core i5 2400 processor and i intend to order for a Zotac GT 710 video card. So i decided to check for the bottle neck percentage from PC Builds. And they suggested that that that graphic card is too weak for that processor at 1080p. So my question is what does the 1080p represent and what is the real meaning graphic card too weak for your processor, because i thought a processor could be weak for the graphics card and not the reverse, Thanks. And also why aren't PCBuilds giving suggestions for bottle necks at 720p and below. Will I be okay if I ignore that warning and order for it anyway?

Answer 1

In order to do anything your graphics card needs instructions. It needs geometry data. It needs positions of objects. It needs textures.

In order to calculate positions of your character model your CPU takes in information from your keyboard and mouse. It has information that shows how the character model changes over time, the model animations. Calculation of position, orientation, animation and so on all require the CPU to do work before passing onto the GPU to draw it.

The instructions might be "simple" from the graphics card point of view: "here is a model, apply these textures" or it could be more complex "take this model, apply transforms to this area or limb to make it look like this".

Having lots of elements in a scene that change position to each other or need on-the-fly transformation can quickly shift the balance from GPU (drawing) bottlenecks to CPU (calculation) bottlenecks. The CPU might be calculating the wider world and movement of objects that are not on-screen yet, but could be at any moment.

It is the type and quantity of calculations in a game or program that determine whether you are CPU or GPU bottlenecked.

If your GPU is constantly waiting for the CPU to give it data on the scene or models then it will not be able to perform at its best. Your GPU is bottlenecked by the CPU.

If your CPU can give your GPU everything it needs before it needs it then your GPU becomes the bottleneck. If your CPU can put out all the information needed to calculate the "world" at 60fps but your graphics card cannot draw it that fast then your GPU is the bottleneck.

If your GPU can put out 60 fps (or your screen refresh rate) without waiting then you are not bottlenecked (except by your display frequency).

All that said, the 710 is a pretty weak card by today's standards. Games have a lot of visual processing going on and I doubt a 710 could process graphics on a modern game to put out a high framerate.