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.
Facebook
Twitter
RSS
173 Comments
View All Comments
Exodite - Tuesday, March 6, 2012 - link
I have absolutely no problem with that.The apt comparison would be the 7900 series though, and those only really fail on price.
Which will likely change if Nvidia brings something competitive to the high end with Kepler.
Lets face it, until the current consoles die in a fire and/or display makers see fit to bring sensibly priced >1080p panels to the desktop there's really no need for more performance in the desktop space.
SlyNine - Monday, March 5, 2012 - link
The fact the things are sitting still.I'm running a 5870 which is basically 75% the performance of a 7970, and I paid 379 for the 5870. Which is also 75% of the cost of a 7970. The price of a 7970 is basically the exact same price structure as the 2 1/2 year old 5870, So we are stuck where we were in 2009, yay.
This is NOT how the computer world is supposed to work, and as big geek, I don't like it.
morfinx - Monday, March 5, 2012 - link
75% performance of 7970 would mean that it's 33% faster than a 5870. And that's just not accurate. I have a 5870 as well, so I was paying a lot of attention on how much faster the 7970 is in various reviews. Everything I've read indicates that it's anywhere from 70-110% faster at 2560x1600 resolution (I run 3600x1920, so likely even even more of a difference). That's not even even considering the massive overclocking headroom of the 7970 vs barely any OC headroom of the 5870. Overclocked, a 7970 is easily twice as fast as a 5870.Alpert - Tuesday, March 6, 2012 - link
The 6950 retailed for $299 and the 6970 retailed for $369 when they were released. 10-25% performance increase for every new series of cards is what to expect. Now we can clearly see these card perform better then the 6950/6970, hell a 7850 overclocks to what a GTX580 is capable of.The value of what was a $600 GTX580 card more then a year ago, The value of a $499 GTX580 today, you get a $300 7850.
The price you pay for performance is always going down just not in big steps.
Logsdonb - Monday, March 5, 2012 - link
These should be excellent cards for crossfire solutions, especially when combined with the new PCI 3.0 bus system. They represent significant improvements in heat, power, and noise at their performance levels. I think these would work well in small form factor gaming PCs, especially when combined with the upcoming Ivy Bridge CPUs, which max out at 77 watts. I don't want a loud, space heater that sucks down massive power for a computer. I have also noticed that cooler systems tend to last longer and have few problems. I feel confident that the prices will come down once the competition from Nvidia comes out next month.I am thinking that we are approaching a really nice time to upgrade if you like balanced systems that deliver excellent gaming performance in reasonable portable packages that wont disturb your personal environment with excess heat and noise. I intend on waiting for Ivy bridge and Kepler before pulling the trigger, but I am eagerly awaiting upgrading evertyhing.
claysm - Monday, March 5, 2012 - link
The price point on the 7xxx series cards seems to be a little too high at the moment, the only advantage they have is that that do outperform the GTX 5xx series cards in a number of ways (power consumption, performance, temps). The biggest problem with the 7xxx series is that they just don't perform that much higher at each price point than AMD's current 6xxx series cards. Why get a 7770 when you can, for the same money and MUCH more performance, get a 6870? The prices will drop when Kepler rolls around I'm sure, but for now, a little too high, given that most of the increases at each price point don't come in the realm of performance.CeriseCogburn - Thursday, March 8, 2012 - link
AMD has been listening to their little screaming fans who wailed that electric usage and core temps are all the rage....So now the amd fans need to PAY UP SOME $$$ for the nice electric consumption and core temp reduction... let's face it - they have told us all for years now those two things alone are well worth a purchase decision, PERIOD.
I guess it's time for them to dig down deep since their Master has responded with everything they declared of utmost importance.
What's wrong AMD fans ?
BrightCandle - Monday, March 5, 2012 - link
I would love to see Anandtech start to look into the stutter/inconsistent frame problems with these modern graphics card reviews. The techreport has been doing a good job in blowing the lid on the problem, but you guys should be able to start to apply pressure to AMD/NVidia to improve the situation. The minimum average is not the worst it can be, the worst frame time is what you need to worry about. Averages over a second just aren't accurate enough.loeakaodas - Monday, March 5, 2012 - link
These look like great performing cards that need a $50~$100 price drop & hopefully nVidia's new offering will force AMD to compete like they did with the legendary 4800 & 5800 series. I was hoping for a sensible upgrade path from my 2x5850's but it doesn't look like that exists yet, at least not at these price points. I'm better off of putting that money towards a large SSD upgrade, otherwise this midrange 2.5 year old system doesn't really beg for an upgrade.ET - Monday, March 5, 2012 - link
The OC 7850 beats everything hands down at the 2560x1600 resolution, which doesn't look right considering the rest of the benchmarks.Also, on the Skyrim benchmark page the writeup has "GPUs GPUs" on it.