SLI / CrossFire FAQs

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Hello and welcome to the forums mate :)

Can you use SLI on a CrossFire board or can you use CrossFire on a SLI board ?
Well , in general , the answer is NO. But it's said that if you hack the drivers , you can use SLI on a CrossFire board or CrossFire on a SLI board.
Caution:There is no guarantee that if you hack the drivers then you use SLI on a CrossFire Motherboard or CrossFire on a SLI board, so do it at your own risk!
 


thx mate, do u know someone that did it ? site's mates?

thx :hello:
 
Just wanted to add a couple links supporting the usefulness of SLI at low res in rare cases like Crysis. You have to look at the 9800GX2 which is basically SLI G92 in a dual PCB single PCI-e slot fashion.

Crysis very high:

1280x1024 4xaa/16xaf
http://www.digit-life.com/articles2/digest3d/0408/itogi-video-cr3-wxp-aaa-1280-pcie.html

Notice the spanking the GX2 does to a single G92 like the 8800GTS 512MB. 30 fps vs 18 fps. No single GPU hits 19 fps in this one.

1280x1024 very high no aa/af
http://www.digit-life.com/articles2/digest3d/0408/itogi-video-cr3-wxp-1280-pcie.html

Even without fsaa/af, it's still 35 fps vs 22 fps showing the playable difference of SLI even at 12x10 no fsaa.


Now going down to 1024x768 with aa, there is still a big difference. 37 fps vs 25 fps:
http://www.digit-life.com/articles2/digest3d/0408/itogi-video-cr3-wxp-aaa-1024-pcie.html

And at a puny 1024x768 no fsaa, it's 38 fps vs 27 fps average.
http://www.digit-life.com/articles2/digest3d/0408/itogi-video-cr3-wxp-1024-pcie.html

There's proof right there that SLI doesn't need high resolution to scale properly. It just needs GPU demanding settings at whatever the resolution.

Anyway, you will notice that the 9800GX2 leads alot of their low res gaming tests. But in most games the single GPU's still do well enough. If you don't hit a CPU limitation, SLI can scale well at low res, whether or not you need dual gpu's to be playable is a different story. But Without question Crysis very high warrants SLI at any resolution as a single GPU struggles.

This goes along with why I think 9600GT or 8800GT SLI is a good option for people to consider over a single GPU of equal pricing. More often than not 9600GT SLI will beat a single 9800GTX, and sometimes it's a crushing. And to be honest, SLI and driver support have matured alot. It would be the rare game where it would lose because of SLI issues, and most of the time those games a single midrange 9600GT or 8800GT will be plenty anyway. It could be a new game needs a patch or driver support for sli to work properly or scale properly. But TWIMTBP usually makes that a top priority for NV to save face. Not saying there aren't good reasons to consider a single GPU vs SLI (there are), but just there are also good reasons to consider certain SLI midrange solutions over a top single gpu. The introduction of the 9600GT and low 8800GT prices have made them excellent SLI options.

 
Thanks alot Paul :) as usuall your information is great and usefull
Yes the drivers have changed alot and i have mentioned that too and also i have talked about the games that are GPU-limited and benefit from SLI even at low resolutions.
Thanks again mate :) i aprreciate it :)
 
:) No problem.

I saw you made the changes and then just saw those Digit-life very high crysis tests this morning and I thought they were worth getting into this thread for some hard data to back up the changes. These were the best low res, very high Crysis benchies I have seen.

Anyway, for anyone considering a high end GPU like a 9800GTX vs. SLI 9600GT. For $250-300 right now (USA anyway), Save money and buy a 8800GTS G92, or go SLI 9600GT or SLI 8800GT. Obviously exact price for everyone (around the globe) varies, so recommendations would change.
Check each game here: http://www.firingsquad.com/hardware/nvidia_geforce_9800_gtx_performance_preview/page4.asp
 
Thanks Paul, Edited again :)
The reason i didn't post those links in the first page is that although they are true and right but i want to write more rather than posting links and as i said i have talked about SLI in low resolutions too.
 
I know this might sound ridiculous after reading this very informative info. about SLI /crossfire. Well I still have something ask which I didn't quite get. I have a sli main board with a Nvidia chip set, running an ATI X1600XT (crossfire card). Now the question is, Can I use another ATI X1600XT (Cross fire or non Crossfire card) to make a SLI? And thanks to you Mazier for this post. I have indeed learned alot what I didn't know before.
 

The short answer is no. The long answer is that it is or at least was possible with hacked drivers on the some hardware. I'd say go with the short answer as the chances of the long one working for you are likely nil. :)
 
Thanks alot Paul for your help :)

To Jeanmarie:
I have talked about it in the first page:
Can you use SLI on a CrossFire board or can you use CrossFire on a SLI board ?
Well , in general , the answer is NO. But it's said that if you hack the drivers , you can use SLI on a CrossFire board or CrossFire on a SLI board.
Caution:There is no guarantee that if you hack the drivers then you use SLI on a CrossFire Motherboard or CrossFire on a SLI board, so do it at your own risk!

And by the way, i am glad you liked it and find it useful
 
Thank you both, Paul and Maziar for take the time to answer my question and clear my doubts😉 and drivers is not my cup of tea since I got no idea of doing it; like I would have taking the risk cos I still will end up with cards I don't want anymore. Thanks again...
 
BTW Maziar, thank you for your dedication to not only update but also follow up peoples ?'s on this FAQ. Like Cleeve's FAQ, it takes dedication to maintain. Much kudos to both of you.
 
Thanks alot mate :) this FAQ would never be good if some guys like you,emp,nuke,4745454b,GreatApe.... wouldn't have helped me with it.
I myself want to update this FAQ with all new technology and other things.

Thanks again for helping me in this thread(and in this forum too) i appreciate it :)
 
I read the article, and several others and have a couple questions/comments. I'm looking at picking up a new high end system soon and the SLI/Crossfire issue came up for me so I've been researching it while shopping for the system.

First the "proprietary" hardware architecture raises a frown from me from both manufacturers. I'm not much into the old system of "my way" -- MicroChannel flopped with that versus the more open EISA standard, which was slower, at that generation and other such attempts at proprietary hardware have flopped over time due to folks getting annoyed about it but, if a "standard" is to be born, it often starts in such a way so it's something I can live with...

One thing that struck me about this all of this: How the 2 technologies seem to run. with respect to "operating" and "deployment/maintenance" If you find errors in this, please let me know.

SLI uses a recognition model similar to the old Voodoo 2 model of drivers that recognize the software "image" for multiple cards to function for a software package. If the drivers don't recognize it, the video config drops back to a 'default' behavior of 1 card and simply skips all the fancy multi-card stuff so, for most "non-supporting" software, you gain nothing from having 2 cards.

That old "Voodoo" model was hel". Every time any of your games or apps were updated, the "image" changed so the card would stop working in dual mode until you updated the drivers. With modern day update services, this shouldn't be a big issue -- it can automate the checking 'in the background' -- but is that going to be from NVidia or from each app manufacturer? (as in any software supporting the system will have to submit app image information to NVidia and NVidia will release the driver updates "when they get to it" or what not... Then you have the "fragmentation" potential as you have 20 different games and apps that get patched differently so each goes out to update the drivers or a consolidated update done daily or what not (meaning you lose "multi-card support" until drivers are updated at times...) See where I'm going with "image" and "drivers"? A LOT of potential changes to your "drivers" if this is still the model being proposed -- just picture a "bad update" where NOTHING recognizes 2 cards or the like...

Crossfire is more transparent to the users. It tries to work with whatever is being sent to the video card. It doesn't require custom drivers to be updated for the cards to recognize the "supporting software" versus the cards trying to render whatever is to be displayed on the screen as best as it is able to. It also only uses the "single card" fall back as a "last resort" after trying to render it with multiple cards based upon "advanced" user configurable settings in the drivers.

Now -- this I gleaned from a few different articles and the issues don't seem covered very well but... As you can see, if one is putting the load on companies to release driver updates with every patch from "hundreds" of application companies while the other is transparent... I think I know which one I'll be more comfortable choosing. That transparency is something I kind of like versus a potentially "busy system" as it keeps updating drivers...

Again, if you have any info on this maintenance "use" side of the 2 technologies, I'd appreciate it. I really don't have much on it beyond references to how SLI decides to "fall back to default mode" and how the Crossfire has configuration options on how multiple cards should handle video output "by default"...
 
That issue you said, if its only with Voodoo then the problem is with Voodoo but if happend in other system manufacturer then its the Nvidia's fault.

Also i will edit this FAQ with new informations about SLI/CrossFire
 
Just wonder do PC games that support multi-gpu configuration (SLI or Crossfire) really experience better Visual Graphics then PC games using single graphics card. Looking for anyone that can give me real world experience answer in this area.
 
I think it would be nice to have a bit about multiple monitors as well.

1) You have 2 or three monitors and two GTX 260s or 3870 X2s . Lets say your middle monitor is 30" and the side monitors are 20-24". Let's also say you have three 20" full screen.

What are the possibilities for gaming? For gaming, will the side monitors be disabled and both cards will power the single monitor? Will all three monitors remain active with the primary monitor getting a boost from the second card? Can all three monitors be used in any game without a solution such as TripleHead2Go?

2) What about dual monitor support? How do these multi card solutions work with them?

I've been told that ATI supports triple monitors by allowing the side monitors to be disabled automatically, whereas Nvidia makes it a pain.

I don't know any of these answers, but sure would like to know. I think it would be a great addition to your fantastic FAQ.
 
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