Introduction
In any gaming system, the two most important parts are your graphics card and your central processing unit (CPU). In system builds these days, it is more than common to spend a majority of your money on a great graphics card while skimping on the CPU. Are the people running 7800GTX's with a puny Athlon64 3000+ getting optimal performance or are their games "CPU limited"? This article finds out.

What does “CPU limited” mean?
Any modern computer game requires a whole lot of silicon muscle to get it running properly. Since the launch of Quake 2, 3D graphics cards have gone from being a novelty bragging right to carrying the brunt of the processing load. Since the architecture of a graphics processing unit (GPU) is specifically designed from the ground up to handle graphics processing, it can provide much better FPS at lower clock speeds than a CPU could ever imagine.

However, this leads to a problem. Since the GPU is so finely tuned towards graphics proessing, it can't handle any other operations. It can only do one thing, and it does it very well. CPU's, on the other hand, are built to handle any type of calculation sent at them, but not very efficiently compared to a specifically designed product like a GPU.

Here's the issue at hand: Games take more than graphics calculations to get them to work. The computer, in addition to graphics, has to process artificial intelligence (AI) calculations for single player games, and handle net code for multiplayer games. Additionally, audio calculations, and more recently, physics calculations, must be done as well as many other behind-the-scenes operations. And on which part of the computer do these tasks fall? Right smack dab on the CPU. In the past year, graphics card technology has advanced to the point that current generation cards don't break a sweat with even the most graphics-intensive games. The processing power of the CPU, however, has not advanced as quickly. This has lead to the biggest problem in performance computing since before graphics cards: the plague of CPU limiting. Put simply, the CPU is not able to handle all the background calculations as quickly as the graphics card can handle the 3D calculations, and thus the CPU is a bottleneck.

How do you find out if you're CPU limited?
The best method involves viewing a demo and using a program such as Fraps to record the FPS achieved, then repeat the process after changing the resolution (and thus the load on the GPU). If the average framerate is not affected by a resolution shift from 800x600 to 1024x768, then your system's performance is being limited by your CPU. It's very straightforward.

The System

• AMD Athlon 64 3500+ (Newcastle core)
• eVGA NVIDIA GeForce 7800GT
• 2x512MB Kingston Value Ram (3-3-3-8)
• eVGA 133-K8-NF41-AX (nForce4 SLI chipset)
• 160GB Maxtor DiamondMax 9
• Creative Sound Blaster Audigy2