AMD's Radeon HD 6970 & Radeon HD 6950: Paving The Future For AMD
by Ryan Smith on December 15, 2010 12:01 AM ESTCompute & Tessellation
Moving on from our look at gaming performance, we have our customary look at compute performance, bundled with a look at theoretical tessellation performance. This will give us our best chance to not only look at the theoretical aspects of AMD’s tessellation improvements, but to isolate shader performance to see whether AMD’s theoretical performance advantages and disadvantages from VLIW4 map out to real world scenarios.
Our first compute benchmark comes from Civilization V, which uses DirectCompute to decompress textures on the fly. Civ V includes a sub-benchmark that exclusively tests the speed of their texture decompression algorithm by repeatedly decompressing the textures required for one of the game’s leader scenes.
Civilization V’s compute shader benchmark has always benefitted NVIDIA, but that’s not the real story here. The real story is just how poorly the 6900 series does compared to the 5870. The 6970 barely does better than the 5850, meanwhile the 6950 is closest to NVIDIA’s GTX 460, the 768MB version. If what AMD says is true about the Cayman shader compiler needing some further optimization, then this is benchmark where that’s readily apparent. As an application of GPU computing, we’d expect the 6900 series to do at least somewhat better than the 5870, not notably worse.
Our second GPU compute benchmark is SmallLuxGPU, the GPU ray tracing branch of the open source LuxRender renderer. While it’s still in beta, SmallLuxGPU recently hit a milestone by implementing a complete ray tracing engine in OpenCL, allowing them to fully offload the process to the GPU. It’s this ray tracing engine we’re testing.
Unlike Civ 5, SmallLuxGPU’s performance is much closer to where things should be theoretically. Even with all of AMD’s shader changes both the 5870 and 6970 have a theoretical 2.7 TFLOPs of compute performance, and SmallLuxGPU backs up that number. The 5870 and 6970 are virtually tied, exactly where we’d expect our performance to be if everything is running under reasonably optimal conditions. Note that this means that the 6950 and 6970 both outperform the GTX 580 here, as SmallLuxGPU does a good job setting AMD’s drivers up to extract ILP out of the OpenCL kernel it uses.
Our final compute benchmark is Cyberlink’s MediaEspresso 6, the latest version of their GPU-accelerated video encoding suite. MediaEspresso 6 doesn’t currently utilize a common API, and instead has codepaths for both AMD’s APP and NVIDIA’s CUDA APIs, which gives us a chance to test each API with a common program bridging them. As we’ll see this doesn’t necessarily mean that MediaEspresso behaves similarly on both AMD and NVIDIA GPUs, but for MediaEspresso users it is what it is.
MediaEspresso 6 quickly gets CPU bottlenecked when paired with a faster GPU, leading to our clusters of results. For the 6900 series this mostly serves as a sanity check, proving that transcoding performance has not slipped even with AMD’s new architecture.
At the other end of the spectrum from GPU computing performance is GPU tessellation performance, used exclusively for graphical purposes. For the Radeon 6900 series, AMD significantly enhanced their tessellation by doubling up on tessellation units and the graphic engines they reside in, which can result in up to 3x the tessellation performance over the 5870. In order to analyze the performance of AMD’s enhanced tessellator, we’re using the Unigine Heaven benchmark and Microsoft’s DirectX 11 Detail Tessellation sample program to measure the tessellation performance of a few of our cards.
Since Heaven is a synthetic benchmark at the moment (the DX11 engine isn’t currently used in any games) we’re less concerned with performance relative to NVIDIA’s cards and more concerned with performance relative to the 5870. So with AMD’s tessellation improvements we see the 6970 shoot to life on this benchmark, coming in at nearly 50% faster than the 5870 at both moderate and extreme tessellation settings. This is actually on the low end of AMD’s theoretical tessellation performance improvements, but then even the geometrically overpowered GTX 580 doesn’t get such clear gains. But on that note while the 6970 does well at moderate tessellation levels, at extreme tessellation levels it still falls to the more potent GTX 400/500 series.
As for Microsoft’s DirectX 11 Detail Tessellation Sample program, a different story is going on. The 6970 once again shows significant gains over the 5870, but this time not against the 6870. With the 6870 implementing AMD’s tessellation factor optimized tessellator, most of the 6970’s improvements are already accounted for here. At the same time we can still easily see just how much of an advantage NVIDIA’s GTX 400/500 series still has in the theoretical tessellation department.
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henrikfm - Wednesday, December 15, 2010 - link
The right numbers for these cards considering the performance:6970 -> 5875
6950 -> 5855
flyck - Wednesday, December 15, 2010 - link
Anand also tested with 'outdated' drivers. It is ofcourse AMD fault to not supply the best drivers available at launch though. But anand used 10.10, Reviews that use 10.11 like HardOcp see that the 6950 performance equally or better than 570GTx!! and 6970 trades blows with 580GTX but is overall little slower (but faster than 570GTX).And now we have to wait for the 10.12 drivers which were meant to be for 69xx series.
flyck - Wednesday, December 15, 2010 - link
my bad anand tested with 10.11 :shame:10.12 don't seam to improve performance.
That said, Anand would it be possible to change your graphs?
Starting with the low quality and ending with the high quality? And also make the high quality chart for single cards only. Now it just isn't readable with SLI and crossfire numbers through it.
According to your results 6970 is > 570 and 6950~570 but only when everything turned on.. but one cannot deduct that with the current presentation.
Will Robinson - Wednesday, December 15, 2010 - link
$740 for HD6970 CrossfireX dominates GTX580 SLI costing over $1000.That's some serious ownage right there.
Good pricing on these new cards and solid numbers for power/heat and noise.
Seems like a good new series of cards from AMD.
prdola0 - Wednesday, December 15, 2010 - link
No, you're wrong. Re-read the graphs. GTX580 SLI wins most of the time.softdrinkviking - Wednesday, December 15, 2010 - link
By a small average amount, and for ~$250 extra.Once you get to that level, you're not really hurting for performance anyway, so for people who really just want to play games and aren't interested in having the "fastest card" just to have it, the 6970 is the best value.
Nfarce - Wednesday, December 15, 2010 - link
True. However AMD has just about always been about value over an all out direct card horsepower war with Nvidia. Some people are willing to spend for bragging rights.But I'm a little suspect on AT's figures with these cards. Two other tech sites (Toms Hardware and Guru3D) show the GTX 570 and 580 solidly beating the 6950 and 6970 respectively in the same games with similar PC builds.
IceDread - Friday, December 17, 2010 - link
You are wrong. HD 5970 in crossfire wins over gtx 580 sli. But anandtech did not test that.ypsylon - Wednesday, December 15, 2010 - link
A lot of people were anxious to see what AMD will bring to the market with 6950/6970. And once again not much. Some minor advantages (like 5FPS in handul of games) is nothing worth writing or screaming about. For now GTX580 is more expensive, but now with AMD unveiling new cards nVidia will get really serious about the price. That $500 price point won't live for long. I expecting at least 50$ off that in the next 4-6 weeks.GTX580 is best option today for someone who is interested in new VGA, if you do own right now 5850/5870/5970 (CF or not) don't even bother with 69[whatever].
duploxxx - Wednesday, December 15, 2010 - link
at that price point a 580 the best buy, get lost. The 580 is way over prized for the small performance increase it has above 570-6970 not to mentioning the additional power consumption. Don't see any reason at all to buy that card.Indeed no need to upgrade from a 58xx series but neither would be to move to a nv based card.