My Experience with SL and SLI

SLI is a graphics card technology designed by Nvidia to allow multiple GPUs to be linked together to speed up graphics rendering, both with DirectX and OpenGL.

http://en.wikipedia.org/wiki/Scalable_Link_Interface

There are different configurations, but what I have tried out over the past week is two 8800GT cards with 512MB of ram in the SLI configuration using an Asus Striker II Formula motherboard and an e3110 Xeon processor. My testing was done windowed but maximized on a 1920x1200 display, using the latest Windlight release candidate. Settings were stock "Ultra", which is, everything on and 256m draw distance.

Aside from the specific motherboard and processor, this is a fairly standard configuration that many may be considering trying. Especially now that the price of the 8800 cards are dropping.

There is a definite lack of information on the internet about how well soemthing like this works with SL, so I thought I would at least offer my experience.

Don't bother.

I first tried it on Vista x64. I found that when I enabled SLI and configured an SL profile to use more than one GPU with Split Frame Rendering, frame rates dropped significantly and rendering actually broke. Alternate Frame Rendering on the other hand rendered perfectly well, but reduced frame rates by more than half. The SLI meter provided by the driver showed that there was no SLI boost at all.

At that point I looked around the internet and found one reference to using SLI Antialiasing instead. Briefly, this splits up antialiasing effort between the two graphics cards, but only one does the rest of the work rendering frames. Considering that AA is off in SL anyway, performance will be, at best, the same, but probably slower - but with a prettier Windlight experience.

This is when I discovered that Nvidia's Vista driver doesn't support SLI Antialiasing. So I installed XP, did the same tests as I did with Vista (same results), and tried SLI Antialiasing. I found that with 8x, frame rates were basically the same, but with anything more, frame rates dropped of noticeably.

So, if you want faster graphics for other applications and games, SLI might still be a good choice. If you're thinking of building, or upgrading a machine for a better SL experience, I would suggest sticking with one (perhaps more expensive) graphics card.

As an aside: people have commented in the past about how laggy the cartel hangout is. I have noticed that my frame rates drop considerably there, and I suspect it's the build itself. There are lot of textures!

I've had this experience too. SLI can be fantastic, for programs that are made to use it, but SL is not one of those programs.

Wow, how opportune is this thread. I just got an 8800GT and an SLI-capable motherboard, and was pondering the question of whether, down the road, I would get another GT. (Incidently, I'm very happy with the GT ... great price/performance point for SL).

Thanks for publishing your legwork, Love & Yumi!
.

I just thought I'd throw in my experience with SL and SLI as well and I have to say I completely agree with the original poster on the matter. I had no increase in performance at all running SL in SLI mode, if anything I may have had a small decrease in performance. This was running Windows XP with a pair of 256mb 7600GT video cards. Considering the extra heat generated, power requirements and the increased fan noise, I couldn't wait to pull that second card out after testing.

Since then I have upgraded to a single 320mb 8800GTS and am very happy with the performance of that card.

Thats what I'm running too! And I love it!

Would've gotten 512mb but they werent in my price range at the time.

Still, SLI & SL is not likely to be any improvement. Most software that can use SLI is written to take advantage of it. SL, as Yummi said, is not.

I'm running SLI with 2 8600's now i will tell you yes i went the cheapy route to run sli on my pc but for good reason. 95% of the games out there, including alot of the newer ones, DO NOT take advantage of the SLI technology. Now this isn't to say well it doesn't take SLI but it takes Radeons version of the dual video technology (drawing a blank on the name atm). Because from what i have seen almost no programs run it. Is it bad to have SLI? I highly doubt it. Does it help? To be completely honest, I haven't a freaking clue. I actually plan on running some tests with having my pc run SLI and not run SLI. Using multiple programs (obviously ones that do not utilize the SLI configuration). Who knows, maybe it makes the FPS better. If I have a chance this weekend to run tests to see if it makes any kind of difference in any case or form I will post the results either here or on a seperate post.

I predict a long post on the virtues of SLI used with SL.

Interesting info, I'm planning my next PC, and was thinking of headingt that path of SLI, , now maybe I will just go for a bigger memory 8800, or the latest, is a 9600 isn't it?

There are a number of games and applications that take advantage of SLI and others that are soon going to have more SLI support. Most work with SLI turned on anyway.

To really take advantage of SLI one needs a quad core processor.

Fraps seems to have an issue with SLI in some games, requiring switching to one GPU.

Chiman, the ATI version is called Crossfire.

Radeon simply got the word out about Crossfire to the game industry in a faster way. (Either that or the game industry realizes that the ATI cards can use all the help they can get!)

SLI restored my virginity

I just got a new system with a quadcore processor and a single 512MB 8800GT card, and it screams! I'm really happy with SL's performance with this setup, and I can't imagine SLI making it any better - I think bandwidth is a bigger bottleneck than the machine at this point.

This configuration has really come down in price now so no reason not to go that route and not bother with SLI, unless you play other games that support it (which I don't).

Why do you say that? Anecdotal evidence suggests that quad procs are pretty well useless for gaming at the moment.

I was and still am considering a new machine and this post had definitely convinced me that I DO NOT, need SLI!

I only subscribe to SL! So one good high end Nvidia card will definitely do for my requirements!

Thanks for the information.

My experience is just the opposite, Love. I don't run SLI very often since I use dual monitors, but when I do enable it, my FPS in SL boosts a good 30%. That's HUGE.

I run SL with all settings turned on and maxed, 512 draw, and with 16XQ anti-aliasing.

My system is very different from yours, though. Here the relevant specs:

Windows XP Media Center 2002 SP2
Intel QX6700 Core2 Extreme (quad) 2.66 GHz
EVGA 680i SLI Motherboard
(2) EVGA nVidia 8800GTX 768MB
(2) Eizo Flexscan S2411W 24" 1920x1200

The three most significant differences, obviously, are the OS, the CPU, and the GPU's. There are distinct dissimilarities between the 8800GT and the 8800GTX, and there's a world of difference between the dual core workstation CPU you have, and the gaming-intended quad core CPU I have. Also, SLI under Vista has always been problematic. It wasn't even an option until relatively recently. I realize you repeated your tests with XP, so maybe that issue is moot, but still, I think it's important to emphasize it.

I don't know for certain specifically what factor(s) make or break the SLI experience with SL. But I do know that reported results tend to vary drastically from machine to machine.

Heh, I'm done with Vista. I had high hopes for it, but it's a big pile of rubbish. Not just for SLI either.

I was trying to figure out where my bottleneck is. My cores seem to average out to about 25% utilization (which is not even a thread running constantly), so it's not the CPU. I've turned down the graphics settings to see the frame rate change very little, so I kinda think my problem isn't the graphics rendering either. Something else is holding it back, but I can't imagine what. I suspect that it's nothing as simple as a black box approach to work it out, and probably some understanding of the implementation of the client is required.

I should point out that when I was reading the FPS, I waited until everything was loaded (as much as possible anyway - the client is always refetching textures over and over for some odd reason). But I did wait until the network bandwidth meter settled down.

It is very odd. It's unfortunate that there isn't a GPU framerate test built into the client, since FPS is dramatically affected by location, direction you're facing, and of course, your settings. I would be curious to see how your setup compares to mine.

I don't seem to be having the problems some people have with Vista, but I will say there is no reason to go Vista over XP-SP2. If you have the option, stay XP. It needs much less memory for the same performance.

My opinion only. YMMV

Ok so I kinda thumbed thru the responses since last night, Quad Core actually has no significant basis when dealing with SLI or Crossfire (thanks for that btw) Quad core is simply for better processing, running multiple applications at the same time and running high process programs. Be it server usage or high end programs that would suck the life out of your pc. Quad core was designed to split the work load a little better. I'm running the top of the line AMD processor which is a Dual Core, wether it would run better under a quad core I couldn't tell you off the bat, I do know someone that has a quad core and could pretty easily find out by running graphics tests on both machines, more then likely, I would put money down that the quad core would run only slightly better then a Dual core with the same amount of processing power (gig).

"The Intel Core 2 Extreme Quad-Core processor is a multitasking monster, so users can do more in less time. Significant improvements in system responsiveness are possible because certain tasks can be off-loaded to specific cores. Users can now take on several tasks at once, such as rendering a video, playing a game, or working on basic productivity software, because additional processor resources are free to handle other tasks."

Thats a quote off of tigerdirect specifically talking about the WX9650. It won't hinder the SLI but it certainly won't help it. The programs will run better thats no doubt. But it won't make the SLI run better or faster, the video is split into 2 parts. Your graphics end, and your CPU end. So yes it may seem better from pc to pc, but thats only because the response time may be better on a higher or more core cpu.

Ok I'm sure some of you are either saying he's full of it or haven't a freaking clue what I'm talking about. Think about it this way. The CPU is your brain, the SLI is your eyes, the better the eyes the better the picture right? The more powerful the brain the better it can interpret the information. Does this mean Quad is better then Dual? WELL DUH! Was SLI designed for quad? I highly doubt it. If it was I wouldn't be sitting here right now on this machine typing to you. I would have bugs and glitches out the butt.

* Intel® or AMD® compatible motherboard
* At least 512MB system RAM
* PCI Express® compliant motherboard
* A minimum 300W system power supply
* 50MB of available hard disk space
* CD-ROM or DVD-ROM drive
* Microsoft® Windows® 2000, XP or Vista
* VGA or DVI-I compatible monitor

thats the minimal system requirements for the SLI cards, be it 1 or 2. If this was designed for quad it would say at least dual core but suggested quad for optimal performance. But enough rambling about quads and duals. I will say the "lag" on the graphics end has been solved since i built this machine. Granted my old machine was about 5 years old lol. SLI I feel is a great inovation, which some of you may or may not know they do have boards that utilize 3 video cards instead of just 2 or 1. Will this be something thats huge soon? Probably. Does alot use it now? No. Crysis doesn't utilize it, COD4 does not, TONS of games that are concidered to be "high end gaming" do not utilize the use of SLI. But again as I said before its not exactly clear if it improves even if the SLI is not utilized. Personally, I can't see how it hurts anything if its not used, aside from teh fact that the investment is what 150-800 bucks per card, which personally i think it a bit steep if its barely ever being used. As I said before i'll play with some things, turn the sli on and off and run programs that don't use SLI and see if it makes any difference. More then likely it won't do a damn thing different but just to put the mind at ease I think it will be worth the effort and few hours of work to finally put misconceptions to rest or verify possibilties.