AMD's Radeon HD 5870: Bringing About the Next Generation Of GPUs
by Ryan Smith on September 23, 2009 9:00 AM EST- Posted in
- GPUs
AA Image Quality & Performance
With HL2 unsuitable for use in assessing image quality, we will be using Crysis: Warhead for the task. Warhead has a great deal of foliage in parts of the game which creates an immense amount of aliasing, and along with the geometry of local objects forms a good test for anti-aliasing quality. Look in particular at the leaves both to the left and through the windshield, along with aliasing along the frame, windows, and mirror of the vehicle. We’d also like to note that since AMD’s SSAA modes do not work in DX10, this is done in DX9 mode instead.
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AMD Radeon HD 5870
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AMD Radeon HD 4870
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NVIDIA GTX 280
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| No AA | ||
| 2X MSAA | ||
| 4X MSAA | ||
| 8X MSAA | ||
| 2X MSAA +AAA | 2X MSAA +AAA | 2X MSAA + SSTr |
| 4X MSAA +AAA | 4X MSAA +AAA | 4X MSAA + SSTr |
| 8X MSAA +AAA | 8X MSAA +AAA | 8X MSAA + SSTr |
| 2X SSAA | ||
| 4X SSAA | ||
| 8X SSAA |
From an image quality perspective, very little has changed for AMD compared to the 4890. With MSAA and AAA modes enabled the quality is virtually identical. And while things are not identical when flipping between vendors (for whatever reason the sky brightness differs), the resulting image quality is still basically the same.
For AMD, the downside to this IQ test is that SSAA fails to break away from MSAA + AAA. We’ve previously established that SSAA is a superior (albeit brute force) method of anti-aliasing, but we have been unable to find any scene in any game that succinctly proves it. Shader aliasing should be the biggest difference, but in practice we can’t find any such aliasing in a DX9 game that would be obvious. Nor is Crysis Warhead benefitting from the extra texture sampling here.
From our testing, we’re left with the impression that for a MSAA + AAA (or MSAA + SSTr for NVIDIA) is just as good as SSAA for all practical purposes. Much as with the anisotropic filtering situation we know through technological proof that there is better method, but it just isn’t making a noticeable difference here. If nothing else this is good from a performance standpoint, as MSAA + AAA is not nearly as hard on performance as outright SSAA is. Perhaps SSAA is better suited for older games, particularly those locked at lower resolutions?
For our performance data, we have two cases. We will first look at HL2 on only the 5870, which we ran before realizing the quality problem with Source-engine games. We believe that the performance data is still correct in spite of the visual bug, and while we’re not going to use it as our only data, we will use it as an example of AA performance in an older title.
As a testament to the rendering power of the 5870, even at 2560x1600 and 8x SSAA, we still get a just-playable framerate on HL2. To put things in perspective, with 8x SSAA the game is being rendered at approximately 32MP, well over the size of even the largest possible single-card Eyefinity display.
Our second, larger performance test is Crysis: Warhead. Here we are testing the game on DX9 mode again at a resolution of 1920x1200. Since this is a look at the impact of AA on various architectures, we will limit this test to the 5870, the GTX 280, and the Radeon HD 4890. Our interest here is in performance relative to no anti-aliasing, and whether different architectures lose the same amount of performance or not.
Starting with the 5870, moving from 0x AA to 4x MSAA only incurs a 20% drop in performance, while 8x MSAA increases that drop to 35%, or 80% of the 4x MSAA performance. Interestingly, in spite of the heavy foliage in the scene, Adaptive AA has virtually no performance hit over regular MSAA, coming in at virtually the same results. SSAA is of course the big loser here, quickly dropping to unplayable levels. As we discussed earlier, the quality of SSAA is no better than MSAA + AAA here.
Moving on, we have the 4890. While the overall performance is lower, interestingly enough the drop in performance from MSAA is not quite as much, at only 17% for 4x MSAA and 25% for 8x MSAA. This makes the performance of 8x MSAA relative to 4x MSAA 92%. Once again the performance hit from enabling AAA is miniscule, at roughly 1 FPS.
Finally we have the GTX 280. The drop in performance here is in line with that of the 5870; 20% for 4x MSAA, 36% for 8x MSAA, with 8x MSAA offering 80% of the performance. Even enabling supersample transparency AA only knocks off 1 FPS, just like AAA under the 5870.
What this leaves us with are very curious results. On a percentage basis the 5870 is no better than the GTX 280, which isn’t an irrational thing to see, but it does worse than the 4890. At this point we don’t have a good explanation for the difference; perhaps it’s a product of early drivers or the early BIOS? It’s something that we’ll need to investigate at a later date.
Wrapping things up, as we discussed earlier AMD has been pitching the idea of better 8x MSAA performance in the 5870 compared to the 4800 series due to the extra cache. Although from a practical perspective we’re not sold on the idea that 8x MSAA is a big enough improvement to justify any performance hit, we can put to rest the idea that the 5870 is any better at 8x MSAA than prior cards. At least in Crysis: Warhead, we’re not seeing it.
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Zool - Sunday, September 27, 2009 - link
The speed of the on chip cache just shows that the external memory bandwith in curent gpus is only to get the data to gpu or recieve the final data from gpu. The raw processing hapenns on chip with those 10 times faster sram cache or else the raw teraflops would vanish.JarredWalton - Sunday, September 27, 2009 - link
If SD had any reading comprehension or understanding of tech, he would realize that what I am saying is:1) Memory bandwidth didn't double - it went up by just 23%
2) Look at the results and performance increased by far more than 23%
3) Ergo, the 4890 is not bandwidth limited in most cases, and there was no need to double the bandwidth.
Would more bandwidth help performance? Almost certainly, as the 5870 is such a high performance part that unlike the 4890 it could use more. Similarly, the 4870X2 has 50% more bandwidth than the 5870, but it's never 50% faster in our tests, so again it's obviously not bandwidth limited.
Was it that hard to understand? Nope, unless you are trying to pretend I put an ATI bias on everything I say. You're trying to start arguments again where there was none.
SiliconDoc - Sunday, September 27, 2009 - link
The 4800 data rate ram is faster vs former 3600 - hence bus width is running FASTER - so your simple conclusions are wrong.When we overlcock the 5870's ram, we get framerate increase - it increases the bandwidth, and up go the numbers.
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Not like there isn't an argument, because you don't understand tech.
JarredWalton - Sunday, September 27, 2009 - link
The bus is indeed faster -- 4800 effective vs. 3900 on the 4890 or 3600 on the 4870. What's "wrong about my simple conclusions"? You're not wrong, but you're not 100% right if you suggest bandwidth is the only bottleneck.Naturally, as most games are at least partially bandwidth limited, if you overclock 10% you increase performance. The question is, does it increase linearly by 10%? Rarely, just as if you overclock the core 10% you usually don't get 10% boost. If you do get a 1-for-1 increase with overclocking, it indicates you are solely bottlenecked by that aspect of performance.
So my conclusions still stand: the 5870 is more bandwidth limited than 4890, but it is not completely bandwidth limited. Improving the caches will also help the GPU deal with less bandwidth, just as it does on CPUs. As fast as Bloomfield may be with triple-channel DDR3-1066 (25.6GB/s), the CPU can process far more data than RAM could hope to provide. Would a wider/faster bus help the 5870? Yup. Would it be a win-win scenario in terms of cost vs. performance? Apparently ATI didn't think so, and given how quickly sales numbers taper off above $300 for GPUs, I'm inclined to agree.
I'd also wager we're a lot more CPU limited on 5870 than many other GPUs, particularly with CrossFire setups. I wouldn't even look at 5870 CrossFire unless you're running a high-end/overclocked Core i7 or Phenom II (i.e. over ~3.4GHz).
And FWIW: Does any of this mean NVIDIA can't go a different route? Nope. GT300 can use 512-bit interfaces with GDDR5, and they can be faster than 5870. They'll probably cost more if that's the case, but then it's still up to the consumers to decide how much they're willing to spend.
silverblue - Saturday, September 26, 2009 - link
I suppose if we end up seeing a 512-bit card then it'll make for a very interesting comparison with the 5870. With equal clocks during testing, we'd have a far better idea, though I'd expect to see far more RAM on a 512-bit card which may serve to skew the figures and muddy the waters, so to speak.Voo - Friday, September 25, 2009 - link
Hey Jarred I know that's neither the right place nor the right person to ask, but do we get some kind of "Ignore this person" button with the site revamp Anand talked about some months ago?I think I'd prefer this feature about almost everything - even an edit button ;)
JarredWalton - Friday, September 25, 2009 - link
I'll ask and find out. I know that the comments are supposed to receive a nice overhaul, but more than that...? Of course, if you ignore his posts on this (and the responses), you'd only have about five comments! ;-)Voo - Saturday, September 26, 2009 - link
Great!Yep it'd be rather short, but I'd rather have 10 interesting comments than 1000 COMMENTS WRITTEN IN CAPS!!11 with dubious content ;)
SiliconDoc - Wednesday, September 30, 2009 - link
I put it in caps so you could easily avoid them, I was thinking of you and your "problems".I guess since you "knew this wasn't the right time or place" but went ahead anyway, you've got "lot's of problems".
Let me know when you have posted an "interesting comment" with no "dubios nature" to it.
I suspect I'll be waiting years.
MODEL3 - Friday, September 25, 2009 - link
Hi Ryan,Nice new info in your review.
The day you posted your review, i wrote in the forums that according to my perception there are other reasons except bandwidth limitations and driver maturity, that the 850MHz 5870 hasn't doubled its performance in relation with a 850MHz 4890.
Usually when a GPU has 2X the specs of another GPU the performance gain is 2X (of cource i am not talking about games with engines that are CPU limited or engines that seems to scale badly or are poor coded for example)
There are many examples in the past that we had 2X performance gain with 2X the specs. (not in all the games, but in many games)
From the tests that i saw in your review and from my understanding of the AMD slides, i think there are 2 more reasons that 5870 performs like that.
The day of your review i wrote to the forums the additional reasons that i think the 5870 performs like that, but nobody replied me.
I wrote that probably 5870 has:
1.Geometry/vertex performance issues (in the sense that it cannot generate 2X geometry in relation with 4890) (my main assumption)
or/and
2.Geometry/vertex shading performance issues (in the sense that the geometry shader [GS] cannot shade vertex with 2X speed in relation with 4890)(another possible assumption)
I guess there are synthetic benchmarks that have tests like that (pure geometry speed, and pure geometry/vertex shader speed, in addition with the classic pixel shader speed tests) so someone can see if my assumption is true.
If you have the time and you think that this is possible and you feel like it is worth your time, can you check my hypothesis please?
Thanks very much,
MODel3