Eyefinity

Somewhere around 2006 - 2007 ATI was working on the overall specifications for what would eventually turn into the RV870 GPU. These GPUs are designed by combining the views of ATI's engineers with the demands of the developers, end-users and OEMs. In the case of Eyefinity, the initial demand came directly from the OEMs.

ATI was working on the mobile version of its RV870 architecture and realized that it had a number of DisplayPort (DP) outputs at the request of OEMs. The OEMs wanted up to six DP outputs from the GPU, but with only two active at a time. The six came from two for internal panel use (if an OEM wanted to do a dual-monitor notebook, which has happened since), two for external outputs (one DP and one DVI/VGA/HDMI for example), and two for passing through to a docking station. Again, only two had to be active at once so the GPU only had six sets of DP lanes but the display engines to drive two simultaneously.

ATI looked at the effort required to enable all six outputs at the same time and made it so, thus the RV870 GPU can output to a maximum of six displays at the same time. Not all cards support this as you first need to have the requisite number of display outputs on the card itself. The standard Radeon HD 5870 can drive three outputs simultaneously: any combination of the DVI and HDMI ports for up to 2 monitors, and a DisplayPort output independent of DVI/HDMI. Later this year you'll see a version of the card with six mini-DisplayPort outputs for driving six monitors.

It's not just hardware, there's a software component as well. The Radeon HD 5000 series driver allows you to combine all of these display outputs into one single large surface, visible to Windows and your games as a single display with tremendous resolution.

I set up a group of three Dell 24" displays (U2410s). This isn't exactly what Eyefinity was designed for since each display costs $600, but the point is that you could group three $200 1920 x 1080 panels together and potentially have a more immersive gaming experience (for less money) than a single 30" panel.

For our Eyefinity tests I chose to use every single type of output on the card, that's one DVI, one HDMI and one DisplayPort:

With all three outputs connected, Windows defaults to cloning the display across all monitors. Going into ATI's Catalyst Control Center lets you configure your Eyefinity groups:

With three displays connected I could create a single 1x3 or 3x1 arrangement of displays. I also had the ability to rotate the displays first so they were in portrait mode.

You can create smaller groups, although the ability to do so disappeared after I created my first Eyefinity setup (even after deleting it and trying to recreate it). Once you've selected the type of Eyefinity display you'd like to create, the driver will make a guess as to the arrangement of your panels.

If it guessed correctly, just click Yes and you're good to go. Otherwise ATI has a handy way of determining the location of your monitors:

With the software side taken care of, you now have a Single Large Surface as ATI likes to call it. The display appears as one contiguous panel with a ridiculous resolution to the OS and all applications/games:


Three 24" panels in a row give us 5760 x 1200

The screenshot above should clue you into the first problem with an Eyefinity setup: aspect ratio. While the Windows desktop simply expands to provide you with more screen real estate, some games may not increase how much you can see - they may just stretch the viewport to fill all of the horizontal resolution. The resolution is correctly listed in Batman Arkham Asylum, but the aspect ratio is not (5760:1200 !~ 16:9). In these situations my Eyefinity setup made me feel downright sick; the weird stretching of characters as they moved towards the outer edges of my vision left me feeling ill.


Dispite Oblivion's support for ultra wide aspect ratio gaming, by default the game stretches to occupy all horizontal resolution

Other games have their own quirks. Resident Evil 5 correctly identified the resolution but appeared to maintain a 16:9 aspect ratio without stretching. In other words, while my display was only 1200 pixels high, the game rendered as if it were 3240 pixels high and only fit what it could onto my screens. This resulted in unusable menus and a game that wasn't actually playable once you got into it.

Games with pre-rendered cutscenes generally don't mesh well with Eyefinity either. In fact, anything that's not rendered on the fly tends to only occupy the middle portion of the screens. Game menus are a perfect example of this:

There are other issues with Eyefinity that go beyond just properly taking advantage of the resolution. While the three-monitor setup pictured above is great for games, it's not ideal in Windows. You'd want your main screen to be the one in the center, however since it's a single large display your start menu would actually appear on the leftmost panel. The same applies to games that have a HUD located in the lower left or lower right corners of the display. In Oblivion your health, magic and endurance bars all appear in the lower left, which in the case above means that the far left corner of the left panel is where you have to look for your vitals. Given that each panel is nearly two feet wide, that's a pretty far distance to look.

The biggest issue that everyone worried about was bezel thickness hurting the experience. To be honest, bezel thickness was only an issue for me when I oriented the monitors in portrait mode. Sitting close to an array of wide enough panels, the bezel thickness isn't that big of a deal. Which brings me to the next point: immersion.

The game that sold me on Eyefinity was actually one that I don't play: World of Warcraft. The game handled the ultra wide resolution perfectly, it didn't stretch any content, it just expanded my viewport. With the left and right displays tilted inwards slightly, WoW was more immersive. It's not so much that I could see what was going on around me, but that whenever I moved forward I I had the game world in more of my peripheral vision than I usually do. Running through a field felt more like running through a field, since there was more field in my vision. It's the only example where I actually felt like this was the first step towards the holy grail of creating the Holodeck. The effect was pretty impressive, although costly given that I only really attained it in a single game.

Before using Eyefinity for myself I thought I would hate the bezel thickness of the Dell U2410 monitors and I felt that the experience wouldn't be any more engaging. I was wrong on both counts, but I was also wrong to assume that all games would just work perfectly. Out of the four that I tried, only WoW worked flawlessly - the rest either had issues rendering at the unusually wide resolution or simply stretched the content and didn't give me as much additional viewspace to really make the feature useful. Will this all change given that in six months ATI's entire graphics lineup will support three displays? I'd say that's more than likely. The last company to attempt something similar was Matrox and it unfortunately didn't have the graphics horsepower to back it up.

The Radeon HD 5870 itself is fast enough to render many games at 5760 x 1200 even at full detail settings. I managed 48 fps in World of Warcraft and a staggering 66 fps in Batman Arkham Asylum without AA enabled. It's absolutely playable.

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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. Reply
  • 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.
    Reply
  • 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.
    ---
    Not like there isn't an argument, because you don't understand tech.
    Reply
  • 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.
    Reply
  • 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. Reply
  • 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 ;)
    Reply
  • 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! ;-) Reply
  • 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 ;)
    Reply
  • 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.
    Reply
  • 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
    Reply

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