The Radeon HD 4850 & 4870: AMD Wins at $199 and $299
by Anand Lal Shimpi & Derek Wilson on June 25, 2008 12:00 AM EST- Posted in
- GPUs
Fixing AMD's Poor AA Performance
Now that we have a new architecture from AMD with improved AA performance, it's time again to look at a comparison of all the different AA modes these cards offer. No new modes have been introduced since the R600 and G80 reviews, but AMD has completely rebuilt their ROPs with special attention to hardware based AA resolve. In R600, hardware resolve wasn't much faster than shader based resolve, but this time around, AA runs blazingly fast whether its on the dedicated resolve hardware or on the shader hardware (since their is so much more shader hardware now even shader based resolve gets a giant boost).
The first thing we will want to look at are the MSAA modes. These are the modes we absolutely recommend for use with AMD hardware as all their other filters essentially low-pass filter the entire image by blending in neighboring subpixels. In any case, the results are very impressive for RV770.
The RV670 at 19x12 was limited in some way other than AA (it really couldn't keep up), but at 16x10 we can get a better idea of relative impact of AA. And clearly the RV770 quite improves fall off with increasing AA levels over the previous generation. One special thing to note is that the RV770 does fall off very gracefully to 8xAA. Since the RV670, G80 and GT200 all have sharp drops in performance when moving up from 4xAA to 8xAA, the RV770 really shines here. In fact, the few tests we did with 8xAA paints the 4870 in a much better light relative to the GTX 280. Remember from our earlier architecture discussion that Oblivion is the game where the GT200 had the largest performance advantage over RV770.
While 8xAA performance is all well and good, the image quality difference is just not enough for us to recommend enabling it over increasing resolution (or better yet, pixel density on LCD panels -- hello display makers). For those with panels that don't go over 1280x1024, it would be better to spend the extra money on a large panel than a $300 graphics card. The application where we see 8xAA making the most sense is on 50+ HDTVs used as computer monitors where the pixels are just plain huge. For the majority of desktop users though 4xAA is where it's at.
We did test the performance of all the other modes as well. NVIDIA's CSAA modes are quite good (they actually improve image quality rather than degrade it), but again, stay away from anything but AMD's "box" filtered AA.
The RV770 actually shows a bigger performance hit from enabling their tent filters than RV670. This is likely because the filters are run on shader hardware in both cases while RV770 has faster hardware resolve that can be used for normal AA resolve. If RV670 resolves "box" filtered AA on the shader as well this would explain the flatter performance in that case. Even more so than the image quality question, the fact that they perform lower really should be the nail in the coffin for AMD's tent filter garbage.
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Final Destination II - Wednesday, June 25, 2008 - link
http://www.techpowerup.com/reviews/Powercolor/HD_4...">http://www.techpowerup.com/reviews/Powercolor/HD_4...Look! Compare the Powercolor vs. the MSI.
Somehow MSI seems to have done a better job with 4dB less.
Final Destination II - Wednesday, June 25, 2008 - link
Try ASUS, 7°C cooler.Justin Case - Wednesday, June 25, 2008 - link
I thought it was only Johan, and it was sort of understandable since he's not a native English speaker, but it seems most Anandtech writers don't know the difference between "its" and "it's"."It's" means "it is" or "it has" (just as "he's" or "she's"). When you're talking about something that belongs to something else, you use "its" (or "his" / "her").
In a sentence such as "RV770 in all it's [sic] glory.", you're clearly not saying "in all it is glory" or "in all it has glory"; you sare saying "in all the glory that belongs to it". So you should use "its", not "it's".
Even if you can't understand the difference (which seems pretty straightforward, but for some reason confuses some people), modern grammar checkers will pick this up 9 times out of 10.
CyberHawk - Thursday, June 26, 2008 - link
I am not a native English speaker, but I am well aware of the difference. I am also sure that reviewers are also ... it's just that - with all this text, we can forgive them, can't we?I have a bachelor of computer science, studying for higher degree, but: I look at the technical side of the article, so I don't even notice the errors :D (although I can tell the difference I simply don't see it while reading)
CyberHawk - Thursday, June 26, 2008 - link
Oh, I forgot: maybe I'm just being too enthusiastic ;)JarredWalton - Wednesday, June 25, 2008 - link
More likely is that with a 10000 word article and four lengthy GPU reviews in two weeks, errors slipped into the text. I know at one point I noticed Derek says "their" instead of "there" as well, and I can assure you that he knows the difference. I know I use Word's grammar checker, but I'm not sure Derek even uses Word sometimes. :)araczynski - Wednesday, June 25, 2008 - link
of the 4850's, slickdeals has posted a sale, between rebate and coupon off...$150 each. can't beat that bang/$ by anything from nvidia.first ati cards that will ever be in my computers since i've started with the voodoo/riva tnt :)
Denithor - Wednesday, June 25, 2008 - link
Page 15: first reference to "GTX 280" should be "GTX 260" instead.Page 19: I think you meant "type" not "time" in this paragraph.
natty1 - Wednesday, June 25, 2008 - link
This review is flawed. It shows greater than 100% scaling for Crossfire 4870 in Call of Duty 4. Why don't they just give us the raw numbers for both single and dual cards in the same scenario? Why use a method that will artificially inflate the Crossfire results?Denithor - Wednesday, June 25, 2008 - link
If you read the comments before yours, you'd see the answer.Experimental error and/or improved scaling for each card versus a single card. Read the earlier comment for more details.