jmke

In this in-depth article we take a look at the performance of the NVIDIA Geforce GTX 280 and ATI Radeon HD 4870 X2 when anti-aliasing is enabled. We test 8 different games at several different AA levels under Windows XP as well as under Windows Vista. How does performance scale when you go from XP to Vista, how much impact does enabling AA have? Read on to find out!

http://www.madshrimps.be/gotoartik.php?articID=869

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Kaotik

You forgot to mention that
...8xAA on ATI should be compared to 8xQAA on nV, not the 8xAA which is 4xMSAA based CSAA mode
...16xAA on ATI effectively turn the card into single chip card which can do 16xMSAA, since both chips render the same frame with different AA patterns
...16xAA on nV is 4xMSAA based CSAA mode and 16xQAA on nV is 8xMSAA based CSAA mode

So 16x and 8x comparisons in your graphs are far from being 'fair' or 'apples-to-apples', the 8xAA should have ATI 8xAA vs nV 8xQAA (8xQAA = 8xMSAA) and 16xAA shouldn't even exist since the GTX280 can't do 16xMSAA which is (practicly) what the HD4870X2 is doing by blending the same frame rendered twice with different AA patterns.

jmke

Thank you for your input. much appreciated; the 16xAA on the ATI does indeed split performance in two, really heavy hit on performance, but ultimate image quality.

While the performance on the two cards at different AA levels can be compared head to the head in the charts, their scaling going from XP to Vista was definitely my main focus.

I don't know if you were the same person who email me about this same issue, but I agree with you that NVIDIA and ATI each have their own approach to the AA levels defined in their control panel, making it less than straight-forward.

on the topic of AA levels, I was hard pressed to find major improvement on NVIDIA going from 4xAA to 16xQAA (through NV control panel); same goes for ATI where 4xAA or 8xAA did little to improve image quality visually, meaning that the to be able to spot the difference you'll have to do screenshot comparisons of static screens and use a zoom-loop in order to find them.

on the upside, we finally almost get free 4xAA under Vista with ATI which will be a key feature for full DX11 compliance if I remember correctly.

Again thank you for your input and the educative message!


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I received the following mail regarding Crysis performance with the HD 4870 X2 (and Crossfire)

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Kaotik

Nah, I'm not the same person, it was another Beyond3D user as far as I know who mailed you.

I just thought that those differences should be mentioned even though the comparison between Vista & XP was the main concern of the great article.

Regarding the 'free 4xAA' on HD4870X2 you mentioned, I think you're mixing it with the DX10.1 requirement of 4xAA, which has nothing to do with performance, just that you have to have the support for it (as far as I know, DX10.1 was the first DX ever to actually require support for specific AA mode)

jmke

I've added an addendum to the article regarding the difference in AA levels between ATI and NVIDIA

I thought DX10.1 (and DX11) allowed 4xAA without a performance hit, much like Assassin's Creed on the ATI cards before they released the patch

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Kaotik

Nope, there's no such thing as "free AA" really even though the performance drops are relatively small today. DX10.1 (or 11) changes nothing on these regards, 10.1 just introduced the requirement to have support for 4xMSAA to be 10.1 compliant, and allows access to the samples "better" (no idea how to better describe it really)
In case of Assassin's Creed, they took advantage of DX10.1 how they can access the AA samples later in the rendering too, with DX10 they had to do two rendering passes for some effects, one with and one without AA, while with DX10.1 they could just re-use the buffers from AA rendering pass, completely dropping out one rendering pass.