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

Alien Vs. Predator

The test results yield two charts: the first shows the utilization of the hardware (CPU and GPU) in percentages and the second focuses on graphics performance using different core counts.

The results are not sorted, but the order remains the same throughout the article. In the first chart,we always list the Core i5 CPU employing one core first (black bar) followed by the GeForce GTX 460 GPU (green bar). Next is the dual-core CPU + GPU followed by the 3 GHz quad-core CPU + GPU. Finally, we show the overclocked 4 GHz quad-core CPU + GPU. In each case, the number of bars corresponds to the number of CPU cores, and the average CPU or GPU utilization is shown as a numerical percentage value.

One more word about CPU performance: the load may be divided between several cores in a number of these benchmarks, but the only relevant thing to notice is the level of utilization. Just because the load is distributed between all four cores does not mean that the game fully supports multi-core CPUs. Ideally, all cores would then be utilized at close to 100 percent. Load distribution and management eats some CPU power. You'll be able to see quite clearly when all four cores are really fully utilized in a game like Grand Theft Auto 4.

If the quad-core 3 GHz CPU is not fully taxed in a game, you should see lower utilization compared to the overclocked 4 GHz CPU, since the processor is even less of a bottleneck. For example, this can clearly be seen in Alien vs. Predator, a game in which the graphics card is the obvious bottleneck. This allows you to get away with having a slower CPU and not negatively impact performance.

In the second chart, you see the frame rates of our different CPU and GPU combinations as differentiated by the number of active CPU cores. This chart for Alien vs. Predator confirms what we just mentioned. The GPU is such a tight bottleneck that it hardly matters whether you have a single-core or an overclocked quad-core CPU. If you want to increase frame rates in this game, you'll have to upgrade the graphics card. The game uses 750 MB of graphics memory, which is almost as much as the GeForce GTX 460 makes available.

  • adonn78
    Its True GTA4 can use 1.68GB of Video RAM at 1920x1200. And up to 1.8GB at higher res. The game can get pretty choppy unless you got a 2GB video card and a quad core. They even fixed the shadows so that they use less VRAM but it still craves GPU memory.
  • karma831
    It was nice to see CPU and GPU load percentages.
  • experimentxx
    Best read for a pc gamer..
  • Tamz_msc
    good article, cant wait for part 2!
  • It would have nice to see what is making my favorite game Company Of Heroes be bottle-necked. I have a GTX 480 and an AMD 955@3.4 GHz and i still get laggy frame rates when there is heavy action and weather. Settings all maxed out on dx10 at 1400x900. I heard that the hard drive is what it makes it lag...
  • NuclearShadow
    GTA IV is one of the few games that I could actually see the performance difference with my own eyes when I was on my i7 920 rig with 6 GB of ram and a 4890 when I overclocked. That was a pretty damn good rig (and still is)

    Something I was amazed by in this article is that games like MW2 give pretty good frame rates when running on a single core. I would have never expected such. 59.1 fps would certainly be acceptable for game-play. Also its a shame to see that so many modern titles really don't take that much advantage having so many cores. It's been more than enough time for this to be adjusted and yet the performance difference in most titles seems minimal between 2 and 4 cores. (or in some cases even 1 core) At this rate everyone is going to commonly have 12 core CPU's and most games will still only truly utilize two.
  • baracubra
    OMG this is exactly the article I've been craving since my upgrade from 8800GT SLI to GTX 470.
    I have a Q6600 @ 3.6 but in BF:BC2 I only get around 40% GPU load and 80% CPU. However, my frame rates are in-line with those in this article...

    Anyway I really look forward to the next article!!!!
  • Even though its an older game, i would really like to see crysis in part 2.
  • skora
    This needs to be a staple and have a section in the charts! This is by far one of the most useful articles I've read in a long time and really get down to what matters based on title. Great job TK!!!!!!!!!!!!

    Chris, make a section in the charts for this and keep them updated please!!!!!
  • archange
    You need a better GPU. With the GTX 460 768 MB, the bottleneck shifts strongly towards the GPU, making a comparison between dual/quad cores and 3 to 4 GHz quite pointless.

    This is best showcased by the introduction of the HD 5870 in single and crossfire mode - in the last chart - you can really see FPS picking up.