Conclusion: A Trend Toward 3+ Cores
The latest 3D engines aren't doing Intel or AMD any favors. Somehow, something seems a bit off here. When most games used DirectX 9, you needed a really fast CPU, and these weren't terribly common before the 65 nm fab node due to thermal issues. Transitions to 65, and then 45 nm allowed processor manufacturers and overclockers to accelerate clock frequencies, making 3.5 GHz a breeze with most CPUs.
But the newer DirectX 10 and 11 games don't really need this speed. This change snuck up on us, making CPU overclocking for 3D games rather meaningless at the mainstream level. Of the 20 games tested in this article, only 10 respond at all to CPU overclocking when we used a GeForce GTX 460 graphics card. Seven of them show only small reactions. Just three show a small frame rate increase. Now, this situation might be completely different at lower resolutions, but the Radeon HD 5800-class monitors, the GeForce GTX 460, and HD resolution LCD monitors are slowly becoming standard gaming equipment.
The following table provides an overview of all the test results so that you can check whether your PC is ready for the tested games or if you need to upgrade something. If you are looking for an upgrade, we show what you should replace first. All of the games deliver higher frame rates with better graphics cards. The average optimal number of CPU cores suggested by the test results is 2.75, showing a clear trend towards at least three CPU cores. The age of dual-core CPUs is certainly not over yet, since DirectX 11 yet again puts the focus on graphics card performance. But with the help of better supply and pricing, the market is trending toward quad-core CPUs nonetheless (or at least dual-core chips with Hyper-Threading). Overclocking the CPU is quite pointless when playing games with high quality graphics settings and HD resolutions--unless you already own a pair of flagship graphics cards rendering cooperatively able to shift the bottleneck back to the host processor.
| Games and Impact Factors | GPU Performance Impact | Recommended Number of CPU Cores | Game Response to CPU Overclocking |
|---|---|---|---|
| Alien vs. Predator | yes | 1 | no |
| Alpha Protocol | yes | 2 | no |
| Anno 1404 | yes | 2 | no |
| Avatar | yes | 4 | no |
| Battlefield: Bad Company 2 | yes | 4 | somewhat |
| Bioshock 2 | yes | 2 | somewhat |
| Call of Duty: Modern Warfare 2 | yes | 2 | somewhat |
| Divitiny 2: Ego Draconis | yes | 2 | no |
| Dragon Age: Origins | yes | 4 | somewhat |
| GTA 4 EFLC | yes | 4 | yes |
| Just Cause 2 | yes | 2 | no |
| Kane & Lynch 2 | yes | 2 | no |
| Left 4 Dead 2 | yes | 4 | yes |
| Mass Effect 2 | yes | 4 | somewhat |
| Metro 2033 | yes | 2 | no |
| Prince of Persia: Forgotten Sands | yes | 2 | somewhat |
| Stalker Call of Pripyat | yes | 2 | somewhat |
| StarCraft II | yes | 4 | no |
| Supreme Commander 2 | yes | 4 | yes |
| Wolfenstein | yes | 2 | no |
Giving a straight answer regarding the amount of graphics memory you need is difficult. The games adapt. If less memory is available, less is often used. The feeling we get is that the 768 MB of our Nvidia GeForce GTX 460 graphics card is already starting to feel somewhat insufficient, although it's still fine for most games, so long as you aren't cranking up the anti-aliasing. At a 1920x1200 resolution, 8xAA, and 16xAF in a DirectX 11 game, you should aim for at least 1 GB of graphics memory.
The question of whether the CPU or GPU is most important is easily answered. If you don't have a multi-core CPU, then upgrade it. If you have a dual-core CPU at around 3 GHz, then invest your money into a graphics card, as most games are GPU-limited. This is not something that will change with new DirectX 11 games.
