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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shadowteam - Wednesday, June 25, 2008 - link
Did you know these chips can do up to 125C? 90C is so common for ATI cards, I haven't had one since 2005 that didn't blow me hair dry. Your NV card was just a bad chip I suppose. Why do you think NV or ATI would spend a billion dollars in research work, then let its product burn away due to some crappy cooling? They won't give you more cooling than you actually need. It's the same very cards that go to places like Abu-Dhabi, where room temps. easily hit 50C+.soloman02 - Wednesday, June 25, 2008 - link
Sorry, but no human would survive a temp of 50C.http://en.wikipedia.org/wiki/Thermoregulation#Hot">http://en.wikipedia.org/wiki/Thermoregulation#Hot
In fact the highest temp a human has survived was recorded by the Guinness book of world records as: 46.5C (115.7F). Keep in mind that was the internal temp of the guy. The temp on that day was 32.2C (90F).
http://www.powells.com/biblio?show=0553587129&...">http://www.powells.com/biblio?show=0553587129&...
http://www.time.com/time/magazine/article/0,9171,9...">http://www.time.com/time/magazine/article/0,9171,9...
If it is 50C in those rooms, the people inside are dead or dying.
The cards are probably fine. All it takes is to search google to back up your figures (or to disprove them like I just did).
shadowteam - Wednesday, June 25, 2008 - link
You're just a dumb pissed off loser. There's a big difference in internal human temperature to its surroundings. In places like Sahara, temperatures routinely hit 45C, and max out @ 55C. But does that mean people living there just die? No they don't, because they drink a lot of water, which helps their bodies get rid of excess heat so to keep their internals at normal temperature (32C). You didn't have this knowledge to share so you decided to Google it instead, and make fool out of yourself. Here, let me break it down for you,You said: "Keep in mind that was the internal temp of the guy"
Exactly, the guy was sick, and when you're sick, your body temperature rises, in which case 46C is the limit of survival. I suggest you take Bio-chemistry in college to learn more about human body, which is another 4 years before you finish school.
Ilmarin - Wednesday, June 25, 2008 - link
I'm not talking about chips failing altogether... just stability issues, similar to what you experience from over-zealous overclocking. Lots of people have encountered artifacting/crashes with stock-cooled cards over the years. If these are just 'bad chips' that are experiencing stability issues at high temps, then there are a lot of them getting through quality control. Of course NV and ATI do enough to make most people happy... but many of us have good reason to be nervous about temperature. I think they can and should do better. Dual slot exhaust coolers should be mandatory for the enthusiast/performance cards, with full fan control capability. Often it's up to the partners to get that right, and often it doesn't happen for at least a couple of months.shadowteam - Wednesday, June 25, 2008 - link
I think it's more profitable for board partners to just roll out a stock card rather than go through the trouble of investing time/money into performance cooling. What I've seen thus far, and it's quite apparent, that newer companies tend to go exotic cooling to get themselves heard. Once they're in the game, it's back to stock cooling. For example, Palit and ECS came up with nice coolers for its 9600s. Remember Leadtek from past years? They don't even do custom coolers any more. ASUS, Powercolor, Gigabyte, Sapphire etc just find it easier to throw in a 3rd party cooler from ZM, TT TR, and call it a day.DerekWilson - Wednesday, June 25, 2008 - link
you know we actually received an updated bios for a certain vendors 4850 that speeds the fan up a bit and should reduce heat ...i suspect a lot of vendors will start adjusting their fan tables actually ...
shadowteam - Wednesday, June 25, 2008 - link
I think this reply was meant for the guy right above me. I'm all for stock cooling :).ImmortalZ - Wednesday, June 25, 2008 - link
"Quake Wars once again shows the 4870 outperforming the GTX 280, but this time it offers essentially the same performance as the GTX 280 - but at half the price. "You mean the 260 in the first instance?
No text in The Witcher page. I assume this is intentional.
Also, I've heard on the web that the 48xx series has dual-link only on one of it's DVI ports. Is this true?
Oh and another thing - why is the post comment page titled "Untitled Page"? :P
rahat5810 - Wednesday, June 25, 2008 - link
Nice cards and nice article. But I would like to point out that there are some mistakes in the article, nothing fatal though. Like, not mentioning 4870 in the list of cards, writing 280 instead of 260, clicking on the picture to enlarge not working for some of the figures.feelingshorter - Wednesday, June 25, 2008 - link
AMD almost has a perfect card but the fact that the 4870 idles at 46.1 more watts than the 260 means the card will heat up people's room. At load, the difference of 16.1 watts more for the 4870 is forgivable.If its possible to overclock a card using software (without going into BIOS screen), then why isn't it possible to underclock a card also using software when the card's full potential isn't being used? I'd really be interested in knowing the answer, or maybe someone just hasn't asked the question?
I hardly care about Crysis, its more a matter of will it run Starcraft II with 600 units on the map without overheating. Why doesn't anandtech also test how hot the 4870 runs? Although the 4850 numbers aren't pretty at all, the 4870 is a dual slot cooler and might give better numbers right? I only want to know because, like a lot of readers, i have doubts as to whether a card like the 4850 can run super hot and not die within 1+ years of hardcore gaming.