GPU Scaling, or Monitor Scaling?

Discussion in 'Videocards - AMD Radeon Catalyst Drivers Section' started by thechiweenie, Apr 10, 2008.

  1. thechiweenie

    thechiweenie Active Member

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    GPU:
    Sapphire HD 3850 512mb PCI-E x16
    Well I didn't realize the reasons my games where crashing was because of GPU scaling I had set, lol so now they are all set at 1920x1200... I just purchased a Gateway FPD2485W TFT LCD Monitor, lovely picture. And GPU scaling enabled by default, but the monitor has its on built in scaling also. So after thinking something was wrong with my computer, but finding that running a game in windowed mode and then setting to 1920x1200 closing and re-opening worked fine, I was dumbfounded. Then I realized I had GPU Scaling on, and when disabled I had no issues, so my question is two fold I guess! A) do I need GPU Scaling at all? and B) I have switched from Scale Image to full screen size to Maintain Aspect Ratio, I have been unable to test anything out to see if that worked because now all my games are at the proper res! But would Maintain Aspect Ratio work better I wonder?
     
  2. sdack

    sdack Banned

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    GPU:
    ATI Radeon X850XT AGP 256MB
    By default you should disable GPU scaling just as you should disable everything else that is unnecessary. It, as you seem to have experienced, creates new areas of problems as well as can cause a loss in performance.

    You then only use GPU scaling if your monitor cannot do any proper scaling for you and only should you do up-scaling of a low resolution. Down-scaling a high resolution to a lower one so that it can fit your monitor's actual size is a waste. Better set it to 1:1 and use anti-aliasing if you want to improve image quality.

    How well GPU scaling works I do not know. Set your GPU's resolution to one that is just a little bit smaller than what your monitor can do and watch the difference when you enable GPU scaling. Some monitors are only capable of a dumb extrapolation, filling up every 2nd or 3rd pixel with the value of that of a neighbour. This will result in some thin lines appearing twice as thick and makes text almost unreadable. A better way is to do a linear extrapolation where the missing pixels get the average colour value of its neighbours. I doubt that any monitor or GPU will do a bicubic extrapolation which would result in an even better quality. If nothing works well you can try using an even smaller resolution for you GPU and see how well that does.

    If you should keep the aspect ratio or not is then a matter of taste. Some people just seem to love it when scenes gets stretch or compressed only for the sake that it then fills their entire monitor. If you do that you probably eat fast-food that is 2 days old, too. In some cases a change in the aspect ratio can make the result of the extrapolation better as well as worse.

    Sven
     
  3. AcceleratorX

    AcceleratorX Master Guru

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    GPU:
    GTX 560 Ti OC
    The GPU scaling function is done within the display pipeline AFAIK, and has no effect whatsoever on the 3D pipeline. So in general there should be zero performance loss, with the only perceivable difference being slightly extra GPU activity at idle or an extra degree in the temperature charts.

    GPUs these days have specialized hardware to do scaling. AFAIK this involves the RAMDACs, and nowhere have I heard (and I have seen from personal experience as well) that using GPU scaling does not cause a performance loss.

    In general I never faced any problems using this as well, but the setting is highly dependent on both your monitor and the drivers, so I wouldn't be surprised if someone was having problems. :)
     
    Last edited: Apr 19, 2008

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