The Game Rundown: Finding CPU/GPU Bottlenecks, Part 1

Wondering if your favorite game wants more CPU or GPU muscle? We tested 20 different titles using a GeForce GTX 460 and a Core i5 processor (one of our favorite configs) in order to figure out where a solid mainstream machine gets hung up.

There are several questions we're often asked about CPUs and GPUs that we wanted to answer in this article:

  • Do I need a quad-core CPU or is dual-core enough?
  • What would be the performance impact of mixing a powerful graphics card with a weak CPU?
  • Should I invest my money in a better processor or faster graphics?
  • How much GPU and CPU performance do I need for HD-class gaming?


Of course, we already have a wealth of information on the site covering these questions indirectly. You can start with Paul Henningsen's Building A Balanced Gaming PC series, and read back through Parts 1-4, all of which are linked here.

For this article, we go after each question head-on. We decided to abandon our usual benchmarking style and instead focus solely on actual in-game results, experienced first-hand. Throughout multiple runs, we tried to keep the real-time gaming consistent, but a slight margin of error was unavoidable. Some slight fuzziness in the results was a fair trade-off in order to reach our true goal: analyzing the CPU and GPU under actual gaming conditions to show just how those two components can hold each other back, influence results, and even help each other.

To answer the questions above, we modified our BIOS settings in order to test different CPU performance levels--so you're not just going to see the results with a stock Core i5 processor. We settled on a base clock frequency of 3 GHz, as this should be within reach for many of today's overclockable mainstream CPUs. We then forced the Core i5 to run in single-, dual-, and quad-core configurations to test and verify multi-core optimizations in our games. As a best-case scenario, the quad-core Core i5 was overclocked to 4 GHz--a reasonable clock rate for this particular model given heat, power consumption, voltage, and stability considerations.

The CPU was paired with a GeForce GTX 460 (768 MB), which is sufficient for most games at HD resolutions. In a few cases, we used the more powerful AMD Radeon HD 5870 to illustrate differences in graphics performance more clearly. Testing was done at a 1920x1200 resolution. Anti-aliasing and anisotropic filtering were set to 8xAA and 16xAF whenever possible via in-game settings to keep the results independent from AMD- and Nvidia-specific driver options. No special software or executable tweaks were used to force anti-aliasing on, meaning that if we were not able to activate a given setting in the game options, then we simply didn't use it. Our 20 games spanned from DirectX 9 to DirectX 11.

This article is Part 1, and it discusses the first 10 games. Part 2 will include test results from 10 more games, overall results, and conclusions.