Topic Title: 7970 supersampling problem?
Topic Summary: low fps
Created On: 03/08/2013 07:51 AM
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 03/08/2013 07:51 AM
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domfather
Peon

Posts: 15
Joined: 02/11/2011

Hello all im getting bad frame rate and stuttering gamplay when using supersampling and ingame AA 8x everygame is practcily unplayble. i thought a 7970 should have no problems with these settings. but it dosent seem to be the case.an example is skyrim. at multisampling 8x frame rate  was 59-60 but changing the aa mode to supersampling reduced it to as low as 19fps and horrible stutter this is with everygame.is it normal to get this kind of performance with supersampling?

 03/08/2013 10:44 AM
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Vantharas
Polygon Pusher

Posts: 3505
Joined: 03/01/2009

Sounds about right. Going from 8X AA to 32X AA is a massive performance hit. 



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 03/08/2013 11:13 AM
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black_zion
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Joined: 04/17/2008

Agreed, especially considering the texture sizes used in modern games are much larger than they were in the 90s and early 2000s, as well as the resolutions which have increased from 1024x728 to 1920x1080. As well the TES games are known for using an abhorrently high number of polygons for the most simple of things, such as grass.

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ASUS Sabertooth 990FX/Gen3 R2, FX-8350 w/ Corsair H60, 8 GiB G.SKILL RipjawsX DDR3-2133, XFX HD 7970 Ghz, 512GB Vertex 4, 256GB Vector, 240GB Agility 3, Creative X-Fi Titanium w/ Creative Gigaworks S750, SeaSonic X750, HP ZR2440w, Win 7 Ultimate x64
 03/08/2013 08:02 PM
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Thanny
Alpha Geek

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Joined: 07/13/2009

I don't think you understand the nature of supersampling.  If you enable 8xSSAA with a resolution of 1920x1080, you're doing the equivalent of rendering at a screen resolution of 15,360x8640.  That's over 132 million pixels per frame to render. 

Why would you think any GPU can do that in a modern game with no problem?

As a quick experiment, I ran Mass Effect (with frame rate smoothing disabled) using various AA settings.  Resolution was 2560x1600, and I have two 7970's in CF at 1200/1500.

I loaded a save from the galaxy console on the Normandy bridge, and had the character turn around to look at a particular spot on the wall (toward the front of the ship is CPU bound to about 130fps).  Here are the results:

  • No AA - 305fps
  • 8xMSAA - 203fps
  • 4xSSAA - 137fps
  • 8xSSAA - 82fps
  • 8xMLAA - 148fps

As you can see, there's a substantial decrease in frame rate going from 8xMSAA to 8xSSAA.  Moreover, because of the deferred rendering of the Unreal 3 engine that Mass Effect uses, none of the traditional AA methods works on all surfaces.  The only one that truly anti-aliases the entire scene is MLAA, a software method that acts on the completely rendered frame, which can render some in-game text unreadable.

 

 03/08/2013 11:00 PM
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black_zion
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Which is why Multisample AA was developed. As you can see from Thanny's benchmarks, 8x MSAA has nearly 4x the performance of 8xSSAA, and I doubt that you could tell the difference between them.

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ASUS Sabertooth 990FX/Gen3 R2, FX-8350 w/ Corsair H60, 8 GiB G.SKILL RipjawsX DDR3-2133, XFX HD 7970 Ghz, 512GB Vertex 4, 256GB Vector, 240GB Agility 3, Creative X-Fi Titanium w/ Creative Gigaworks S750, SeaSonic X750, HP ZR2440w, Win 7 Ultimate x64
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