AMD Radeon HD 7870 GHz Edition & Radeon HD 7850 Review: Rounding Out Southern Islands
by Ryan Smith on March 5, 2012 12:01 AM ESTFurther Image Quality Improvements: SSAA LOD Bias and MLAA 2.0
The Southern Islands launch has been a bit atypical in that AMD has been continuing to introduce new AA features well after the hardware itself has shipped. The first major update to the 7900 series drivers brought with it super sample anti-aliasing (SSAA) support for DX10+, and starting with the Catalyst 12.3 beta later this month AMD is turning their eye towards further improvements for both SSAA and Morphological AA (MLAA).
On the SSAA side of things, since Catalyst 9.11 AMD has implemented an automatic negative Level Of Detail (LOD) bias in their drivers that gets triggered when using SSAA. As SSAA oversamples every aspect of a scene – including textures – it can filter out high frequency details in the process. By using a negative LOD bias, you can in turn cause the renderer to use higher resolution textures closer to the viewer, which is how AMD combats this effect.
With AMD’s initial release of DX10+ SSAA support for the 7900 series they enabled SSAA DX10+ games, but they did not completely port over every aspect of their DX9 SSAA implementation. In this case while there was a negative LOD bias for DX9 there was no such bias in place for DX10+. Starting with Catalyst 12.3 AMD’s drivers have a similar negative LOD bias for DX10+ SSAA, which will bring it fully on par with their DX9 SSAA implementation.
As far as performance and image quality goes, the impact to both is generally minimal. The negative LOD bias slightly increases the use of higher resolution textures, and thereby increases the amount of texels to be fetched, but in our tests the performance difference was non-existent. For that matter in our tests image quality didn’t significantly change due to the LOD bias. It definitely makes textures a bit sharper, but it’s a very subtle effect.
Original uncropped screenshots
| 4x SSAA | 4x SSAA w/LOD Bias |
Moving on, AMD’s other AA change is to Morphological AA, their post-process pseudo-AA method. AMD first introduced MLAA back in 2010 with the 6800 series, and while they were breaking ground in the PC space with a post-process AA filter, game developers quickly took the initiative 2011 to implement post-process AA directly into their games, which allowed it to be applied before HUD elements were drawn and avoiding the blurring of those elements.
Since then AMD has been working on refining their MLAA implementation, which will be replacing MLAA 1.0 and is being launched as MLAA 2.0. In short, MLAA 2.0 is supposed to be faster and have better image quality than MLAA 1.0, reflecting the very rapid pace of development for post-process AA over the last year and a half.
As far as performance goes the performance claims are definitely true. We ran a quick selection of our benchmarks with MLAA 1.0 and MLAA 2.0, and the performance difference between the two is staggering at times. Whereas MLAA 1.0 had a significant (20%+) performance hit in all 3 games we tested, MLAA 2.0 has virtually no performance hit (<5%) in 2 of the 3 games we tested, and in the 3rd game (Portal 2) the performance hit is still reduced by some. This largely reflects the advancements we’ve seen with games that implement their own post-process AA methods, which is that post-process AA is nearly free in most games.
| Radeon HD 7970 MLAA Performance | |||||
| 4x MSAA | 4x MSAA + MLAA 1.0 | 4x MSAA + MLAA 2.0 | |||
| Crysis: Warhead | 54.7 |
43.5 |
53.2 | ||
| DiRT 3 | 85.9 | 49.5 | 78.5 | ||
| Portal 2 | 113.1 | 88.3 | 92 | ||
As for image quality, that’s not quite as straightforward. Since MLAA does not have access to any depth data and operates solely on the rendered image, it’s effectively a smart blur filter. Consequently like any post-process AA method there is a need to balance the blurring of aliased edges with the unintentional burring of textures and other objects, so quality is largely a product of how much burring you’re willing to put up for any given amount of de-aliasing. In other words, it’s largely subjective.
Original uncropped screenshots
| Batman AC #1 | Batman AC #2 | Crysis: Warhead | Portal 2 | |
| MLAA 1.0 | Old MLAA | Old MLAA | Old MLAA | Old MLAA |
| MLAA 2.0 | New MLAA | New MLAA | New MLAA | New MLAA |
From our tests, the one thing that MLAA 2.0 is clearly better at is identifying HUD elements in order to avoid blurring them – Portal 2 in particular showcases this well. Otherwise it’s a tossup; overall MLAA 2.0 appears to be less overbearing, but looking at Portal 2 again it ends up leaving aliasing that MLAA 1.0 resolved. Again this is purely subjective, but MLAA 2.0 appears to cause less image blurring at a cost of less de-aliasing of obvious aliasing artifacts. Whether that’s an improvement or not is left as an exercise to the reader.
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Galidou - Monday, March 5, 2012 - link
Yep, this must be the best price/performance ratio the 7xxx series has to offer yet but still nothing worth of buying unless you got a 3 years old plus video card...7870 priced at 300$ I wouldn't mind changing my 6850 crossfire for one of those considering the wattage and temperature of my actual setup. I was considering a gtx580 as they can be found on ebay for around 400$ used but this 7870 is around the same in every game I play at the resolution I play them. Plus the 2gb memory and cheaper price tag for a new one...
But I'll still wait for the price to drop or switch to kepler if price/performance is amazing... Heard it should be but it's all speculation on something that's not out yet...
chizow - Tuesday, March 6, 2012 - link
Only took 4th product launch from AMD for you to see what I was saying was true, but better late than never. ;)But yeah the real value right now is the last-gen parts going EOL and selling for extremely low prices. The 6950/6970s are mostly dried up in the channel, but there were GTX 480s for $219 last week, up next on the chopping block should be the 560Ti448/570/580 for great prices ahead of Kepler's launch.
Galidou - Tuesday, March 6, 2012 - link
I never said that you were totally wrong, I was only saying that it's not the worst thing that's ever happened in computer's history, while you were making a freaking case of it because I spoke against Nvidia...And you still can't name even an older radeon card in your short list of cheap video cards to get... At 130$ and 160$ for a radeon 6850 and 6870 respectively you still get ALOT for what you pay for. Radeon 6870 isn't far from gtx 560ti. Why mentioning it when you're being paid by the green goblin, they would stop sending your fanboy checks I guess, just teasing :P
There's one thing extraordinary about this gen, the size plus wattage used for THAT kind of performance... is quite amazing, it should just be priced accordingly to it's die size and it would be dirt cheap LOL... but no bang for your bucks here...while in this segment of the market where you usually ''get it all'' about price/performance ratio. Lower the price of 50$ for every 7xxx video card and it will be ALOT better.
BPB - Monday, March 5, 2012 - link
If nothing else I gotta believe that the new nVidia cards will force a quick price adjustment from AMD. I think we'll see the AMD cards drop $25 to $50 when the nvidia cards come out.CeriseCogburn - Friday, March 9, 2012 - link
After running blackbox 2.3 and wenning to the Turkish site I find something very interesting on Kepler:" Nvidia 's next-generation family of Kepler frequencies, dynamic graphics cards needed to improve their own work. Rumor has officially been confirmed as yet have the ability to dynamically overclock Kepler cards will leave a strong impact in the markets."
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LOL - Dynamic Overclocking of Kepler similar to Intel turbo... very nice Nvidia...
http://translate.google.com/translate?hl=en&sl...
mak360 - Monday, March 5, 2012 - link
"but $199 for a GTX 560 Ti is going to be hard to pass up while it lasts" I see you have to get a boot in there to AMD when possible. lolMost of the games are nvidia optimized where the 7850 loses one or two to the 560ti old tech.
AMD`s been quite merciful to nvidia in regards to price points, when nvidia brings it on and the same happens (cards slot in without a challenge to AMD) I call shady business between the two or they don`t want to compete with each other, which is understandable i guess..
Or maybe people need to forget the past and move on with "oh how nice and cheap prices were"
sofreshsoclean2 - Monday, March 5, 2012 - link
smoking card, faster than the 6970, fast as a gtx580 in a lot of those test but 150 smackeroos cheaper It is very close 7950 as well, finally a super fast card that is not 500 bucks. amazing card!! and nice review.thanks
Devoteicon - Monday, March 5, 2012 - link
Upgrade my overclocked 5850 for one of these? Thanks but no thanks.geniusloci - Monday, March 5, 2012 - link
I'm going to be getting one or the other. I'll have to decide if the 7870 is worth the additional cash or not. They will most assuredly drop in price once Nvidia launches its product. Having come from a 560Ti this will feel something like a side grade in performance, but having found out how much better ATIs cards do 2D and video I simply can't return to the blurry mess which is Nvidia right now.Kiste - Monday, March 5, 2012 - link
So it's 2012 and AMD gives us two cards that do little more than match the GTX 570 and 580 in price/performance.Southern Island has been a huge disappointment so far.