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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ET - Monday, March 5, 2012 - link
I agree it's kind of disappointing. Even a 5750 was a good improvement over a 3870, and here there's nothing approaching this kind of performance benefit over the 5870 from these. Though I think part of it is that the 5870 still holds up well in many games, as these benchmarks show.Kjella - Monday, March 5, 2012 - link
I don't think it's that terrible... the 7870 fits pretty much the exact same power envelope as the 5850 and is starting to be a pretty solid performance upgrade. Yes it's a $350 card but inflation adjusted the $279 (pre-hike) 5850 is nearing $300 in 2012 dollars. A good deal and a good cooler (the reference cooler on the 5850 works, but is hardly quiet) and they may get a sale. Just waiting for Ivy Bridge, if nVidia hasn't shown a stunning Kepler by then I think the 7870 is it.Death666Angel - Tuesday, March 6, 2012 - link
Average increase of 40% in performance and you are comparing a high-end graphics card to a mid-range graphics card.DominionSeraph - Monday, March 5, 2012 - link
So, AMD discontinued the $250 6950 and $350 6970 to give us... a $250 6950 and $350 6970.Not exactly impressed.
Looks like it will be up to Nvidia to save us, just as they saved us from the price-gouged 5000 series with aggressive release price of the GTX 460 with price drops on the GTX 470. (That one action set the pricing scheme throughout the 6000/500 series)
CloudFire - Monday, March 5, 2012 - link
I'm not upgrading this cycle but I do wish to see Kepler out sooner to drive down prices. This is business and AMD has a few months of no competition so they are going to do all they can to reap massive profits.Nvidia isn't going to save you, they would do the same thing if they were in AMD's position. Remember nearly 5 years back with the 8800GTX going for 500+ for over a year? Yea......
DominionSeraph - Tuesday, March 6, 2012 - link
A halo product with no competition is beside the point. We're talking about the 7800 series which sits right in a range where there are competing products, and AMD is pricing it to suck you dry.The fact is that the 7000 series is not undercutting the 500 series the way Nvidia undercut the 5000 series. A $250 7850 vs a $270 + free Batman Arkham City GTX 560 Ti 448 Cores is about equal price/performance (maybe a tad in the favor of Nvidia). Contrast this to the GTX 460 being released at $200 when the 5770 was $180. The GTX 460 blew the doors off the 5770 and instantly said the appropriate price for that card is ~$130. A few months later we were seeing $110 5770's and $150 GTX 460's, and that's where we've been at ever since.
AMD refuses to aggressively compete with Nvidia. They simply slot their products into Nvidia's pricing structure. So prices only change when Nvidia drops theirs and AMD is forced to follow. This means that we, the consumers, are dependent on Nvidia to save us, because AMD sure as hell won't.
Exodite - Tuesday, March 6, 2012 - link
Not really a valid point of comparison though.Looking through several reviews of the 7800-series the 7850 lies closer to a 570 than a 560 Ti most of the time, while offering more and better in every possible category.
Sure, the 7850 isn't on the market yet but assuming the ~250 USD pricing holds true I couldn't possibly recommend a 560 Ti, or even 448 core version, over the 7850 with a straight face.
It could still be cheaper, sure, but it's nowhere near the pricing disaster the 7900 and 7700 series are.
To my mind the 7800 series were the ones to wait for.
Granted, with a 6950 myself I won't be upgrading until the 8k-series at the earliest. Unless Kepler turns out truly amazing, and brings triple display functionality on a single card.
tipoo - Monday, March 5, 2012 - link
If I recall Nvidia hasn't really under-priced AMD in recent memory, they've always tried x more performance sold for >x price.ET - Monday, March 5, 2012 - link
"AMD discontinued the $250 6950 and $350 6970 to give us... a $250 6950 and $350 6970."When you put it this way, it's quite a likeable upgrade actually. Slight boost in performance, lower power and better thermals, upgraded features, all for the same price. What's not to like?
chizow - Monday, March 5, 2012 - link
What's not to like is it took them 16 months to put out a greener refresh sidegrade.