Remember this slide?

The "Scalable design" block we already know about, that's RV770 - we reviewed it last month. The 150W TDP $300 part is the Radeon HD 4870, and the 110W $200 part is the Radeon HD 4850, the two cards that have caused NVIDIA quite a bit of pain already. The smaller $100 part has a name, and a release date, neither of which we can talk about at this point, but it's coming.

Today however, is about the 250W, $500 multi-GPU solution - internally known as R700. Hot on the heels of the Radeon HD 4800 series launch, AMD shipped out ten R700 cards worldwide, attempting to capitalize on the success of the 4800 and showcase the strength of AMD's small-GPU strategy.

We're assuming that AMD will call the R700 based cards the Radeon HD 4870 X2, and based on the chart above we're expecting them to retail above $500 (possibly $549?). Today's article is merely a preview as R700s won't be officially launched for at least another month, but AMD wanted to unveil a bit of what it's cooking.


ATI R700 ATI Radeon HD 4870 ATI Radeon HD 4850 ATI Radeon HD 3870
Stream Processors 800 x 2 800 800 320
Texture Units 40 x 2 40 40 16
ROPs 16 x 2 16 16 16
Core Clock 750MHz 750MHz 625MHz 775MHz+
Memory Clock 900MHz (3600MHz data rate) GDDR5 900MHz (3600MHz data rate) GDDR5 993MHz (1986MHz data rate) GDDR3 1125MHz (2250MHz data rate) GDDR3
Memory Bus Width 256-bit x 2 256-bit 256-bit 256-bit
Frame Buffer 1GB x 2 512MB 512MB 512MB
Transistor Count 956M x 2 956M 956M 666M
Manufacturing Process TSMC 55nm TSMC 55nm TSMC 55nm TSMC 55nm
Price Point > $500 $299 $199 $199

The R700 board is literally made up of two RV770s with a PCI Express switch connecting the two. The clock speeds are identical to the Radeon HD 4870, and memory size per GPU has been doubled to 1GB, which could help in hi res cases with AA enabled. In other words, R700 should perform very much like a pair of 4870s in CrossFire. Or should it?

Building a Better CrossFire

When AMD began talking about no longer building high end hardware using single monolithic GPUs a few weeks back, we let them know that improving CrossFire support would be incredibly important going forward. AMD told us that they are putting a lot into that but also that they have some exciting technology up their sleeves with R700 to help out as well. Unfortunately, we haven't gotten as much detailed information on how it works, but the new technology is GPU to GPU communication.

Until now, CrossFire has done zero GPU to GPU or framebuffer to framebuffer communication. As with the first iteration, each card fully renders the parts of the screen for which it is responsible (be it a whole frame in AFR, the top or bottom half of a screen, or alternating tiles). These results are sent to a combiner where the digital signals are merged and output to the screen. This is the only communication that takes place in CrossFire at the moment. R700 will change that by allowing GPUs to communicate.


RV770 has a CrossFire X Sideport...we assume that the two RV770s on a single R700 board somehow connect Sideports and make fast. AMD hasn't told us how yet.

It is not clear how extensive this communication will be, what information will be shared, or how much bandwidth requirements are increased because of this feature. And while it is a step in the right direction, the holy grail of single-card multi-GPU solutions will be a shared framebuffer. Currently both GPUs need a copy of all textures, geometry, etc., and this is a huge waste of resources. While the R700 has 2GB of RAM on board, it will still be limited in many of the same ways a 1GB RV770 would be as each GPU only has access to half the RAM on the card. Of course, since we don't have a 1GB RV770 yet, this card could show some advantages over the single 4870 regardless of CrossFire.

Regardless of where we want (and need) to see multi-GPU technology get to, R700 is the first part to follow AMD's official change in strategy, and as such it will be very important to establish their place in the market and will need to prove to gamers that they are taking the high end seriously. It's great that single-card multi-GPU solutions are capable of providing high end performance, but when spending the amount of money required to put a high end part in your system, people expect compatibility, reliability, and consistent performance. We can't really talk about how well they pull that off with prerelease hardware and prerelease drivers, but we can't emphasize the importance of this enough. We will certainly be putting the screws to it when the hardware does eventually make it out into the wild.

UPDATE: Our initial publication of this article indicated a 2x 512MB framebuffer for a total of 1GB on board. We have since learned that the R700 we tested has 2GB of RAM total for 2x 1GB framebuffers. This has affected some of our analysis and conclusion. We do apologize for any confusion this may have caused.

The Card
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  • David Brown - Monday, April 06, 2009 - link

    Well if you say so, but I am not sure most people would agree...I mean if you really think about it.
    ----------------------------------------
    David Brown
    http://mymmoshop.com/buy/age-of-conan-us/gold/inde...">http://mymmoshop.com/buy/age-of-conan-us/gold/inde...
    Reply
  • granulated - Wednesday, July 23, 2008 - link

    If the charts are all correct then I'm quite astonished that the bizarre results haveb't been highlighted.


    4870 @19x12=73.7fps
    4870CF@19x12=99.8fps


    4870 @25x16=43.9fps
    4870CF@25x16=30.4fps


    plus loads of other bizarre results
    Reply
  • paradoxnighthawk - Friday, July 18, 2008 - link

    I've been an ATi fan since I built my first PC with a 9600 256MB card. I have to say AMD has now proven it can handle the legacy of ATi. I haven't bought a new graphics card for myself since the X1900XT (been waiting for something like this to happen), and in just a short time I will be getting the 4870X2.

    A $500 to be card seems to dominate and combination of alternatives (even more expensive ones) in most applications. If nothing else, this will drive down the price-gauging of nVidia's new GTXs, and make the life of enthusiasts and gamers alike, much more interesting. Regardless, go AMD, bring the competition.

    Afterthought: If only AMD put this much brilliance into their Phenom X3 processors. I think the X3 idea has a lot of potential, just needs some more TLC.
    Reply
  • ilkhan - Thursday, July 17, 2008 - link

    You know what Id really like to see in these reviews?
    Instead of nVidia GeForce / AMD Radeon being repeated in each chart, use the street MSRP for that GPU.

    Then I could get everything I need on one graphic, crysis performance vs the price.

    We KNOW they are going to destroy everything else, so please stop bothering.
    Reply
  • jameswalker - Wednesday, July 16, 2008 - link

    I have 3 ati 4870x2 on an asus workstation motherboard with 4 intel qx9850, i'm going for the 3d mark world record, using linux. Because it is the only operating system that well utilize all 4 cpu's and my 3 video cards. It is water cooled by liquid nitrogen. Reply
  • vailr - Wednesday, July 16, 2008 - link

    Will this 4870 x2 card be commercially available in time for Leo Laporte's "Ultimate Game Machine"?
    Anand had phoned in, to talk on the UGM show:
    http://twitlive.tv/">http://twitlive.tv/
    on July 4 and had offered design tips for the UGM that's being assembled for a late August giveaway. The motherboard/video card selected (then: July 4) was an nVidia 780 motherboard coupled with SLI'ed: two water cooled 9800 GX2 cards:
    http://www.bfgtech.com/bfge98512gtxh2ocwe.aspx">http://www.bfgtech.com/bfge98512gtxh2ocwe.aspx
    Will a water cooled 4870 x2 card be available by mid-August?
    Reply
  • pattycake0147 - Monday, July 14, 2008 - link

    Excellent preview you guys always do a great job on your articles. Is there any news as to when the 790GX chipset is going to be released? Reply
  • dragonbif - Monday, July 14, 2008 - link

    I found a posting of the 1GB version of 4870
    http://www.powercolor.com/Global/products_features...">http://www.powercolor.com/Global/products_features...

    Also I do beleve that the card AnandTech tested is a 2GB 4870x2.
    Reply
  • thewanderer666 - Monday, July 14, 2008 - link

    Anand, I really enjoy your site, but please, get rid of Derek Wilson, not only does he fail miserably at showing that he really knows how to bench video cards (like when he tried to prove how his methodology is better than HardOCP) but he makes huge mistakes in judgement.

    First off, how come he doesn't answer the simple question of how is it possible that you guys, the most respected HW site got an X2 with only 1GB in RAM...many posts talk about this yet he has not even tried to reply. Second, his take on the performance results is simply flawed. If he had read the specs of the X2 as the rest of the sites and noted that the card had 2GB of RAM, the GRID results could have been easily explained by the additional frame buffer memory (1gb vs. 512mb) instead of coming with outlandish remarks about how there are internal aspects of the card that push the performance considerably above a regular crossfire setup.

    As I tell you I really like your site and I respect all of those who write here, but seriously for such a professional site such as yours it's really sad that you have a person like Mr. Wilson in your staff. I hope this is taken as constructive critisism and not as bashing...I'm a long time reader of your site and I have no intention of having anythg different in my mind than helping this site become even better.
    Reply
  • thewanderer666 - Monday, July 14, 2008 - link

    I did see the corrections were made regarding the huge mistakes in the original preview, so kudos for fixing them. Still I stand by my statements about the person in question...this kind of annoying mistakes are becoming more and more common on this site (on the graphics department). Knowing the Anand's professionalism these kind of noob mistakes (how about contacting AMD/ATI and asking them why the results might be so different) should not be allowed. Reply

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