Can someone explain cpu bottlenecking

Discussion in 'Videocards - AMD Radeon Drivers Section' started by Tperk, Dec 27, 2011.

  1. Tperk

    Tperk Member Guru

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    Sorry, I don't really have any experience in this field. Im loving my in game play but i noticed that in Mw3 Im averaging 90fps which is great but then I see that the gpu usage is 50-60% most of the time in game? Does that mean the card ain't working as hard as it could? or? sorry im confused.
     
  2. HamsterCrispy

    HamsterCrispy Master Guru

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    It means that MW3 is not completely GPU based. Not all games use full GPU power. As long as you get reasonable framerates then your good. MW3 uses an engine that is not GPU intensive compared to BF3 where you can see that GPU usage is always 90+%

    And for sure your i7-2700k is NOT a bottleneck :D

    As for the explanation for CPU bottlenecking I think some of the guys here can explain it better than I can -- or you can search on Youtube and look for Linus Tech Tips or NCIX tech tips. Linus explains bottlenecking very concretely.
     
  3. dox_aus

    dox_aus Master Guru

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    Are u averaging 90fps or is that your max? as mw games are capped at 90fps by default.. you need to edit your configs to override it.
     
  4. Tperk

    Tperk Member Guru

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    ah icic sweet thanks i didn't know that about the cap. Every time i glance to that corner im seeing 90.
     

  5. Norezar

    Norezar Active Member

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    It's mostly fairy-tale bull**** that people obsess over and eventually it becomes ingrained regardless of it's relevance or extent.
     
  6. NeuroFunkeR

    NeuroFunkeR Member Guru

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    cpu bottleneck is same as gpu bottleneck, you got powerfull gpu but your cpu is to weak for new games, which causes bad performance, low fps etc.
     
  7. blhealthy4life

    blhealthy4life New Member

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    CPU bottleneck simply put is that your CPU cannot feed your GPU enough information to keep your GPU fully utilized..basically, your GPU is constantly waiting on your CPU for instructions.
     
  8. kevnb

    kevnb Master Guru

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    i think their might be a framerate cap in mw3 of around 90 fps.
     
  9. wafu88

    wafu88 Active Member

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    Hehe, the only response that is correct in this thread.
     
  10. bokah

    bokah Ancient Guru

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    iirc its actually capped at 85fps, but with fraps and most others will show it as 90 for somereason
     

  11. Conker

    Conker Member

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    If your cpu is around 100% usage then your gpu is being bottlenecked by the cpu. If both the gpu and cpu have low usage then its just the game that has poor optimization or the drivers. If the gpu is 100% and the cpu is low then its the gpu thats causing the bottleneck.
     
  12. Mufflore

    Mufflore Ancient Guru

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    or
    has run out of system ram causing paging,
    has run out of gfx ram,
    is bottlenecked by system memory speed,
    is bottlenecked by gfx memory speed,
    is restricted by throttling when running too hot,
    you are using vsync
    ...


    Op,
    If any CPU core (not necessarily the whole CPU) reaches 90 to 100% use, it is bottlenecking the whole game.
     
  13. Lain

    Lain Master Guru

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    Or there just isn't any more game data to process.
     
  14. Hilbert Hagedoorn

    Hilbert Hagedoorn Don Vito Corleone Staff Member

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    You copied that nicely (exactly) out of one of my articles, but'll concur that's my best definition for it.

    :nerd:
     
  15. blhealthy4life

    blhealthy4life New Member

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    Hey.

    With all due respect, I've never read one of your articles nor do I know which article you are referring to...it's not YOUR definition.

    I've been using that defintion of CPU bottlenecking for a very long time...afterall, anyone who knows what CPU bottleneck is should and would say it the same exact way....

    I can probably find several articles on CPU bottleneck where that definition is almost exactly the same...you going to claim that used YOUR definition as well. lol
     
    Last edited: Dec 30, 2011

  16. GrandMax

    GrandMax Member Guru

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    Short bottleneck definition: A bottleneck occurs when maximum fps (or shortest rendering time) is largely limited by a single component, thus impeding the overall system performance. For example, a powerful 6990 coupled with a phenom II typically cannot unleash its full performance because the CPU will be holding it back.

    Here is a list of the most common bottlenecks.

    1. GPU: The most common and the desired bottleneck. You want your GPU to be pushed to its limit. You can check with MSI afterburner and your gpu usage should be near 100%. The goal of a gaming machine is to allow the GPU(s) to work at maximum power.

    2. CPU: The bottleneck you don't want. Expensive to fix, the CPU bottleneck is very annoying. Many Phenom II processor are bottlenecking high-end GPU setups, such as 6990 and mid/high-end CFX setups. I want to clarify something here. The problem is not that the overall CPU performance is lacking, but rather the fact that the single thread (core) that supports rendering will be pushed to its maximum capacity. AMD IPC is bad.

    Also, AMD drivers, as of today, do not support multi-threading rendering. Games can use multiple thread but rendering is limited to one core. DX11 has a fix for that but it is not yet supported in the drivers (neither Nvidia or AMD).

    Personally, I think AMD needs to release a driver for DX11 that supports multi-threading to ensure that their Thuban and Phenom II can be matched with very high end gpu setups.

    As of today, it is not recommended to match a phenom II with more than 400$ of GPU. Also, one may note that some games are so badly coded that they will cpu bottleneck even a 2700k. Skyrim comes to mind.

    Best fix: Overclock that CPU with a proper thermal solution. Make sure the Mobo can take it (8+2 phase).

    3. Vram bottleneck: This is not well documented. When you CFX or SLI a GPU, the Vram is not doubled. However, with such GPU power, you want to crank up the resolution and anti-aliasing as much as possible. This creates some issues. Even if the GPU power is there to support good framerate with these settings, the vram pool will simply be too small. My 6870s are a good example of this. With 1GB of memory, I get some issues/stuttering while pushing AA and resolution in some games.

    Vram appears to be responsible for most min fps in benchmarks. Personally, I care more about min fps than I do about average fps.

    I often assume the games to be scaling poorly due to the CFX profiles but in some cases, it seems to be vram that prevent higher GPU usage. As a rule of thumb, current games may need up to 1.5GB or vram. To have 2GB seems to be futureproof. BF3 requires about 1.5GB at 1080p with 4xMSAA.

    4. RAM: Crysis 2 needs more than 4GB of ram. If the game start caching of you HDD, the framerate with plummet.That is easy to fix.

    5. PCI speed (x8 or x16): Historically not a concern. But that one is tricky, while it does little difference on the average fps for most GPUs. It may influence performance in CFX/SLI mode. Especially is Vram is completely used and hypermemory is used.

    Hope this helps.
     
  17. zhengzhoudave

    zhengzhoudave Master Guru

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    this

    EDIT: whoever came up with the original statement, well done that man!
     
    Last edited: Dec 30, 2011
  18. XL_ence

    XL_ence Maha Guru

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    Lol what?? How could CPU bottleneck be a fairy tale? If you actually knew what CPU bottleneck means, you would not be saying that. Some other people have already explained what it means in this thread.
     
  19. Pill Monster

    Pill Monster Banned

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    The CPU doesn't render anything, it draws frames that are passed to the GPU which does all the rendering.

    It's not a fairy tale, but the B word does get overused a lot....
     
    Last edited: Jan 8, 2012
  20. Conker

    Conker Member

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    In laymen terms.

    Its when the cpu isn't sending information fast enough for the gpu to calculate. You got Point A to Point B. If point A is slowing down a lot then point B has to wait until point A sends information over. This causes a bottleneck. Think of it like a physically pipe.

    For example:
    The water pipes used by cities are huge and thick to distribute water to everyone. The pipe from your house to the street is small and miniature in comparison. The point where the city pipe meets your house pipe is the bottleneck. Not enough bandwidth will lower throughput. This can be used in almost any situation for network bottlenecks, gpu, memory...everything practically.
     

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