AMD Radeon HD 7970 Review: 28nm And Graphics Core Next, Together As One
by Ryan Smith on December 22, 2011 12:00 AM EST- Posted in
- GPUs
- AMD
- Radeon
- ATI
- Radeon HD 7000
Theoreticals & Tessellation
From a rendering perspective one of the most interesting things AMD did with Tahiti was what they didn’t do: they didn’t add more ROPs, they didn’t add more geometry engines. And yet based on our game performance they’ve clearly improved on their performance in those situations by making more efficient use of the hardware they do have.
So we wanted to take a quick look at synthetic performance to see what these tools had to say about AMD’s changes. We’ve included the numbers for every other GPU in our lineup as a reference point, but we would strongly suggest against reading into them too much. AMD versus AMD is sometimes relevant to real world performance; AMD versus NVIDIA rarely is.
We’ll start with 3DMark Vantage and its color fill test. This is basically a ROP test that attempts to have a GPU’s ROPs blend as many pixels as it can. Theoretically AMD can do 32 color operations per clock on Tahiti, which at 925MHz for 7970 means the theoretical limit is 29.6Gpix/sec; not that any architecture is ever that efficient. In practice 7970 hits 13.33Gpix/sec, which is still well short of the theoretical maximum, but pay close attention to 7970’s performance relative to 6970. Even with the same number of ROPs and a similar theoretical performance limit (29.6 vs 28.16), 7970 is pushing 51% more pixels than 6970 is.
In designing Tahiti AMD said that they didn’t need more ROPs they just needed more efficient ROPs, and it looks like they’ve delivered on this. It’s not clear whether this is the limit for efficiency or if AMD can squeeze more out of their ROPs in future designs, but this definitely helps to prove that there’s more to graphics rendering than a large number of functional units.
Our other 3DMark synthetic benchmark is the 3DMark Vantage Texture Blend test, which measures how quickly a GPU can blend multiple FP16 textures. This is more synthetic than most tests because FP16 textures aren’t widely used, but it’s a consistent benchmark.
The theoretical performance improvement from 6970 to 7970 is 40% - 33% more texture units operating at a 5% higher clockspeed. In practice the 7970 exceeds that improvement by increasing texture performance by 46%, meaning the 7970 has benefitted from more than the increase in texture units. Most likely the new cache architecture has further improved the efficiency of the texture units, although the 3DMark texture set is not particularly large.
Moving on, we also wanted to take a look at tessellation. AMD did not increase the theoretical geometry performance of Tahiti as compared to Cayman – both top out at 2 triangles per clock – but AMD has put a lot of effort into improving the efficiency of Tahiti’s geometry units as we’ve seen reflected in our game benchmarks.
Our first tessellation benchmark is the traditional Detail Tessellation sample program from the DirectX SDK. Here we’re looking at tessellation performance as a product of the framerate, testing at tessellation factors 7 (normal) and 15 (max). Traditionally this is a test that has been rather balanced at normal tessellation levels, while NVIDIA cards with their superior geometry throughput have been the top performers at maximum tessellation levels. So it’s all the more interesting when we’ve seen the tables turned; the 7970 is merely competitive with the GTX 580 at normal tessellation levels, but now it’s ahead of the GTX 580 by 24%. More significantly however the 7970 is ahead of the 6970 by 57%.
Our second tessellation benchmark is Unigine Heaven, a benchmark that straddles the line between a synthetic benchmark and a real-world benchmark, as the engine is licensed but no notable DX11 games have been produced using it yet. In any case the Heaven benchmark is notable for its heavy use of tessellation, which means it’s largely a proxy test for tessellation performance.
As with the Detail Tessellation sample program, Heaven shows significant gains for the 7970 versus the 6970, with the 7970 leading by 56%. Meanwhile it leads the GTX 580 by 27%, which is actually slightly better than what we saw under the more “pure” Detail Tessellation sample. Between these two benchmarks it’s clear that AMD’s tessellation efficiency improvements are quite real, and that with Tahiti AMD can deliver much better tessellation performance than Cayman even at virtually the same theoretical triangle throughput rate.
Of course one has to wonder what NVIDIA will have in store for Kepler next year. Their current Fermi design seems to scale well with additional geometry units, but if Tahiti is anything to go by, there’s a great deal to be gained just by focusing on efficiency. NVIDIA has prided themselves on their geometry performance since before GF100 even shipped, so it will be interesting if they have anything in store to hold on to that distinction.
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Ananke - Thursday, December 22, 2011 - link
"The 7970 leads the 5870 by 50-60% here and in a number of other games"...and as I see it also carries 500-600% of price premium over the 5870.Meh, this is so so priced for a FireGL card, but very badly placed for a consumer market. Regardless, CUDA is getting more open meanwhile. AMD is still several generations/years behind in the HPC market and marketing a product above the NVidia price targets will not help AMD to make it popular.
Having say so, I am using ATI cards for gaming for several years already, and I am very pleased with their IQ and performance. I have always pre-purchased my ATI cards... What I am missing though is teh promised and never materialized consumer level software that can utilize its calculation ability, aka CyberLink and other video transcoders. If it was not for the naughty Nvidia power draw in the 5th series, I would've gone green to have CUDA. Hence, considering SO MUCH MONEY, I am waiting at least 6 months from now to see what the prices will be for the both new contenders in next GPU architectures :).
Dangerous_Dave - Thursday, December 22, 2011 - link
Seems like AMD can't do anything right these days. Bulldozer was designed for a world that doesn't exist, and now we have this new GPU stinking up the place. I'm sorry but @28nm you have double the transistors per area compared with @40nm, yet the performance is only 30% better for a chip that is virtually the same size! It should be at least twice as far ahead of the 6970 as that, even on immature drivers. As it stands, AMD @ 28nm is only just ahead of Nvidia @ 40nm as far as minimums go (the only thing that matters).I shudder to think how badly AMD is going to get destroyed when Nvidia release their 28nm GPU.
Finally - Friday, December 23, 2011 - link
I shudder to think how badly one Nvidia fanboy's ego is going to get scratched if team red released a better GPU and his favourite team has nothing to offer.Oh... they did?
CeriseCogburn - Thursday, March 8, 2012 - link
We have to let amd "go first" now since they have been so on the brink of bankruptcy collapse for so long that they've had to sell off most of their assets... and refinance by AbuDhabi oil money...I think it's nice our laws and global economy puts pressure on the big winners to not utterly crush the underdogs...
Really, if amd makes another fail it might be the last one before collapse and "restructuring" and frankly not many of us want to see that...
They already made the "last move" a dying company does and slashed with the ax at their people...
If the amd fans didn't constantly demand they be given a few dollars off all the time, amd might not be failing - I mean think about it - a near constant loss, because the excessive demand for price vs perf vs the enemy is all the radeon fans claim to care about.
It would be better for us all if the radeon fans dropped the constant $ complaints and just manned up and supported AMD as real fans, with their pocketbooks... instead of driving their favorite toward bankruptcy and cooked books filled with red ink...
Dangerous_Dave - Thursday, December 22, 2011 - link
On reflection this card is even worse than my initial analysis. For 3.4billion transistors AMD could have done no research at all and simply integrated two 6870s onto a single die (a la 5870 vs 4870) and ramped up the clock speed to somewhere over 1Ghz (since 28nm would have easily allowed that). This would have produced performance similar to a 6990, and far in excess of the 7970.Instead we've done a lot of research and spent 4.1billion transistors creating a card that is far worse than a 6990!
That's the value of AMD's creative thinking.
cknobman - Thursday, December 22, 2011 - link
The sad part is your likely too stupid to realize just how idiotic your post sounds.They introduced a new architecture that facilitates much better compute performance as well as giving more gaming performance.
Did you read the article and look at the compute benchmarks or did you just flip through the game benchmark pages and look at numbers without reading?
Zingam - Thursday, December 22, 2011 - link
Or maybe you just don't realize that they've added another 2 billion transistors for minimal graphics performance increase over the previous generation.That's almost as if you buy a new generation BMW that has instead 300 hp, 600hp but is not able to drag a bigger trailer.
The only benefit for you would be that you can brag that you've just got the most expensive and useless car available.
Finally - Friday, December 23, 2011 - link
Rule 1A:The frequency of a car pseudoanalogy to explain a technical concept increases with thread length. This will make many people chuckle, as computer people are rarely knowledgeable about vehicular mechanics.
cknobman - Friday, December 23, 2011 - link
Holy sh!t are you not reading and understanding the article and posts here??????????The extra transistors and new architecture were to increase COMPUTE PERFORMANCE as well as graphics.
Think bigger picture here dude not just games. Think of fusion and how general computing and graphics computing will merge into one.
This architecture is much bigger than just being a graphics card for games.
This is AMD's fermi except they did it about 100x better than Nvidia keeping power in check and still having amazing performance.
Plus your looking at probably beta drivers (heck maybe alpha) so there could very will be another 10+% increase in performance once this thing hit retail shelves and gets some driver improvements.
CeriseCogburn - Thursday, March 8, 2012 - link
I see. So when nvidia did it, it was abandoning gamers for 6 months of ripping away and gnawing plus... but now, since it's amd, amd has done it 100X better... and no abandonment...Wow.
I love hypocrisy in it's full raw and massive form - it's an absolute wonder to behold.