Fixing AMD's Poor AA Performance

Now that we have a new architecture from AMD with improved AA performance, it's time again to look at a comparison of all the different AA modes these cards offer. No new modes have been introduced since the R600 and G80 reviews, but AMD has completely rebuilt their ROPs with special attention to hardware based AA resolve. In R600, hardware resolve wasn't much faster than shader based resolve, but this time around, AA runs blazingly fast whether its on the dedicated resolve hardware or on the shader hardware (since their is so much more shader hardware now even shader based resolve gets a giant boost).

The first thing we will want to look at are the MSAA modes. These are the modes we absolutely recommend for use with AMD hardware as all their other filters essentially low-pass filter the entire image by blending in neighboring subpixels. In any case, the results are very impressive for RV770.

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The RV670 at 19x12 was limited in some way other than AA (it really couldn't keep up), but at 16x10 we can get a better idea of relative impact of AA. And clearly the RV770 quite improves fall off with increasing AA levels over the previous generation. One special thing to note is that the RV770 does fall off very gracefully to 8xAA. Since the RV670, G80 and GT200 all have sharp drops in performance when moving up from 4xAA to 8xAA, the RV770 really shines here. In fact, the few tests we did with 8xAA paints the 4870 in a much better light relative to the GTX 280. Remember from our earlier architecture discussion that Oblivion is the game where the GT200 had the largest performance advantage over RV770.

While 8xAA performance is all well and good, the image quality difference is just not enough for us to recommend enabling it over increasing resolution (or better yet, pixel density on LCD panels -- hello display makers). For those with panels that don't go over 1280x1024, it would be better to spend the extra money on a large panel than a $300 graphics card. The application where we see 8xAA making the most sense is on 50+ HDTVs used as computer monitors where the pixels are just plain huge. For the majority of desktop users though 4xAA is where it's at.

We did test the performance of all the other modes as well. NVIDIA's CSAA modes are quite good (they actually improve image quality rather than degrade it), but again, stay away from anything but AMD's "box" filtered AA.

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The RV770 actually shows a bigger performance hit from enabling their tent filters than RV670. This is likely because the filters are run on shader hardware in both cases while RV770 has faster hardware resolve that can be used for normal AA resolve. If RV670 resolves "box" filtered AA on the shader as well this would explain the flatter performance in that case. Even more so than the image quality question, the fact that they perform lower really should be the nail in the coffin for AMD's tent filter garbage.
One, er, Hub to Rule them All? AA Image Quality Comparison


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  • calumhm - Friday, September 11, 2009 - link

    i mean, ATI invented the unified pixel/shader architechture, or so i believe, and this generation they've got dx10.1 level hardware something like 7 months and counting before Nvidia have any.

    Also i once read an article about SLI and Crossfire, about how SLI has only one rendering type, scissors. (meaning the screen is divided in two) Whereas ATI have scissors, tiled, (so that the more demanding areas of the screen are better divided amongst the cards) and others.
    Also, you can combine any HD series ATI card with any HD series card! thats way better than having to say, buy another 7800 for SLI because just one isn't doing it anymore, even though the 9800 series are out. With CFire you could add a 4870 to your old 3870!

    Im currently with Nvidia (a 9600gt (found one for £60!)) but am frequently impressed by ATI.

    -IS- ATI the smart customer's choice?
  • billywigga - Friday, August 29, 2008 - link

    im pretty shore the 4870 is low profile ive been looking everywhere for a low profile graphics card and i think i foung a high ends one unlike the geforce 8400 and the 8600 those arenot very good and they dont look good either but where do i buy the 4870 Reply
  • Hrel - Thursday, August 21, 2008 - link

    Why has there been no article comparing the 8800GT to the 9800GT? Is it just a rebrand, are there noticeable performance differences. It's 9 series, I assume it has hybrid power, but I don't know. Anandtech, PLEASE! Do an article on this. Reply
  • billywigga - Friday, August 29, 2008 - link

    bang for the buck id get the 9800 because its newer also all the diffrence is it has more intagrated ram your saving a lot if you just get more ram to your computer. Reply
  • firewolfsm - Friday, August 01, 2008 - link

    I'm trying to do the same benchmark for Crysis for my 4850 as I have a similar system and a fresh vista install. Just wondering what kind of driver settings you used. Reply
  • spikeysting - Saturday, July 19, 2008 - link

    I just got it for $179 at Frys. Such a good deal. Reply
  • Yangorang - Tuesday, July 08, 2008 - link

    Anyone tried this mod?">
  • jALLAD - Friday, July 04, 2008 - link

    I would for sure go for the 4870. (I am a Quake Wars fan boy u see :P)
    But I was unsure how these would perform on Linux. Is the driver support reliable? Right now I use a 7950 NVIDIA and their support on Linux is almost shite. I was wondering whether its better or worse...

    Anyone ?
  • KriegenSchlagen - Monday, July 07, 2008 - link

    If you are a Quake Wars fan, aren't the scores higher in 3-4 GeForce SLI configs vs. Crossfire mode 4870? Reply
  • jALLAD - Wednesday, July 09, 2008 - link

    well I am looking forward to a single card setup. SLI or CF is beyond the reach of my pockets. :P


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