AMD Radeon HD 7870 GHz Edition & Radeon HD 7850 Review: Rounding Out Southern Islands
by Ryan Smith on March 5, 2012 12:01 AM ESTCompute Performance
Moving on from our look at gaming performance, we have our customary look at compute performance. With GCN AMD significantly overhauled their architecture in order to improve compute performance, as their long-run initiatives rely on GPU compute performance becoming far more important than it is today.
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. Note that this is a DX11 DirectCompute benchmark.
The Civ V compute shader benchmark once again shows off just how much the compute shader performance of the 7800 series has improved relative to the 6900 series, with both 7800 cards coming in well, well ahead of any previous generation AMD cards. Compared to NVIDIA’s lineup the 7800 series does fairly well for itself too, although not quite as well as the commanding lead the 7900 series took.
Our next benchmark is SmallLuxGPU, the GPU ray tracing branch of the open source LuxRender renderer. We’re now using a development build from the version 2.0 branch, and we’ve moved on to a more complex scene that hopefully will provide a greater challenge to our GPUs.
SmallLuxGPU continues to showcase the 7800 series’ improvements over past AMD architectures, and while it’s not the same kind of massive leap we saw with CivV, it’s still enough to bring the 7850 up to near the performance of the 6970, and pushing the 7870 well beyond that. The only real competition here for AMD is AMD.
For our next benchmark we’re looking at AESEncryptDecrypt, an OpenCL AES encryption routine that AES encrypts/decrypts an 8K x 8K pixel square image file. The results of this benchmark are the average time to encrypt the image over a number of iterations of the AES cypher.
On the one hand, the 7870 gets quite close to the 7950 here in our AESEncryptDecrypt benchmark, in spite of the latter’s higher number of shaders. On the other hand, it’s still not enough to dethrone the GTX 570; the only NVIDIA cards the 7800 series can beat start at the GTX 560 Ti.
Finally, our last benchmark is once again looking at compute shader performance, this time through the Fluid simulation sample in the DirectX SDK. This program simulates the motion and interactions of a 16k particle fluid using a compute shader, with a choice of several different algorithms. In this case we’re using an (O)n^2 nearest neighbor method that is optimized by using shared memory to cache data.
In our final compute test the 7800 series once again makes a run at the top, with both cards rising past the GTX 570, although they can’t quite match the GTX 580. In an interesting turn of events the 7870 ends up being some 6% faster than the 7950, in spite of the fact that in a compute benchmark the 7950 should have a solid lead. This just goes to show that core clockspeeds do matter, and that adding more shaders alone can’t conquer all benchmarks.
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Kaboose - Monday, March 5, 2012 - link
7870, beats GTX 570 and is about even with the GTX 580, uses 150watts less power at load, is quieter, is cooler, and has idle power draw > 23watts less. How is this a disappointment? The only disappointment i see is the price which is the result of no competition from Nvidia.Kiste - Monday, March 5, 2012 - link
A new generation of GPUs used to give us a whole hell of a lot more performance at any given price point. The current AMD stuff does not and that is a disappointment.Case in point: you even have to talk these things up by basically saying "oh, well, at least they draw less power".
Kaboose - Monday, March 5, 2012 - link
dropping power consumption by over 50% is something of a gimmick? Dropping load temps by 14c compared to the GTX 570 is not significant? 14c is a fairly large degree of deference, this gives higher room for overclocking as well as a cooler system overall. When Nvidia releases Kepler and we have both companies with 28nm then we can (hopefully) see some competition in price. In my opinion the 7870 at $325 would be a great card right now. Once Kepler is out $285-300 I think would be nice. I agree it is over priced right now however.If Nvidia releases Kepler and gives us a LOT more performance over last generation then I will concede that the 7xxx series is a failure. However from the way AMD is behaving it doesn't appear Kepler is going to do much in terms of raw performance either.
Kiste - Monday, March 5, 2012 - link
While reducing power consumption might not be a gimmick, it is the result of the new process node and thus in itself not particularly impressive, especially when you more or less keep the performance the same as with the previous generation.I'm still not impressed, sorry. Price/performance plain and simply sucks ass with these cards, barely beating the stuff that's on the market right now in that regard.
And even with the high-end SI cards there's barely much of a performance boost compared to what's already been on the market for months.
Sure, less power draw is nice. I won't complain about it but if a brand new generation of GPUs comes out and I am not even one little bit compelled to upgrade from my aging, heavily overclocked GTX570, then something is cleary wrong here.
Exodite - Monday, March 5, 2012 - link
We'll just have to wait and see what Nvidia provides when they finally decide to put competition on the market, won't we?I'd happily agree to finding the 7900-series not as high-performing as I'd like, and the 7700-series too expensive.
From the reviews I've read so far the 7800-series, the 7850 especially, is pretty much the perfect card ATM.
Low power, low noise, cool, 2GB VRAM and runs between a 560 Ti and 570 in performance.
It's definitely the card I'd recommend to anyone at this point, especially given the fact that we'll see better coolers than AMDs atrocities once we get release versions.
Iketh - Monday, March 5, 2012 - link
You must live in a cold climate. You're happy with a heavily overclocked 570?? I live in FL, and that card increases my power bill $30-$70 each month over my 6870 during 3 of the 4 seasons, and I'm talking from experience. Do you have any idea how hard an A/C has to work in a small 2 bedroom house to counter the blast of heat from an overclocked gaming rig??If you live in a hot climate, test it for yourself.
You don't compare just the power draw of the cards themselves....
Kiste - Monday, March 5, 2012 - link
I'm not quite sure if you're actually expecting a serious answer to that kind of hyperbolic drivel.Jamahl - Monday, March 5, 2012 - link
You really don't get it do you? These cards REALLY DO heat up rooms. Where do you think the heat goes? Ever heard of the law of conservation of energy?londiste - Monday, March 5, 2012 - link
oh damn, i need to get two of those, maybe they'll reduce my heating bill at winter :)Kiste - Monday, March 5, 2012 - link
Spelling "really do" in capital letter doesn't make it any more less ridiculous a statement.My whole PC (GPU, OCed CPU, 4 HDDS) draws slightly more than 300W under typical gaming loads. You can't "heat up a room" with that, much less with just the GPU.