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Universal shaders, DirectX 11, Why older cards cant use its features..

Last response: in Graphics & Displays
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a c 172 U Graphics card
January 31, 2011 3:15:01 AM

Just thinking about this the other day. All cards from the last few years have "universal" shaders that can process pretty much anything. Now whiy is it that older cards, such as an 8800gt, can not do DX11 capable things like tesselation? Is it just a driver thing? can someone explain this to me?
a c 363 U Graphics card
January 31, 2011 3:30:53 AM

To the best of my knowledge DX11 requires specific hardware on the GPU. That's why a DX9 or DX10 card cannot do DX11 effects.
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a c 166 U Graphics card
January 31, 2011 5:16:56 AM

Shading is only one component of how a graphics engine works. It's quite complicated.

Even older tesselation hardware isn't compatible with the new tesselation method in DX11.

It should be noted that you need more than an HD5870 to use DX11 practically because DX9/DX10 settings look better at playable frame rates. Metro 2033 is a slideshow on my high-end system with DX11 but looks and runs great without it.

Having said that, I'd never recommend a non-DX11 card to anyone getting a new card but if you have a great non-DX11 setup then DX11 alone is no reason to upgrade.

Further reading:
http://en.wikipedia.org/wiki/Shader

http://www.pcper.com/article.php?aid=858 (good read, even if you don't understand everything. you won't.)

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a b U Graphics card
January 31, 2011 5:37:28 AM

The shaders may be the same, but everything else has changed. What usually happens with old hardware is that they could be programmed to run new things, but they'd probably end up 2x slower.
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a c 172 U Graphics card
January 31, 2011 5:38:34 AM

ah, i get it, although dx11 cards have similar universal shaders of dx10 cards, they are still missing a fixed function tesselation unit among other fixed function units. I suppose it would be possible to do tesselation on an older card given the correct programming, but it would be slow. I remember back in the day ATI had that Truform which is basically the same thing, but not part of DX/openGL There was a big performance hit running Return to Castle Wolfenstein with truform turned on on my old radeon 8500, but when i got a 9800xt it worked well and looked great.
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a c 172 U Graphics card
January 31, 2011 6:48:33 PM

Best answer selected by iam2thecrowe.
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a c 272 U Graphics card
January 31, 2011 7:26:45 PM

This topic has been closed by Mousemonkey
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