Dmdally

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May 14, 2012
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Hey I just had a quick question about AMD Graphics Cards and SLI connection. I have an ASUS Maximus V Gene mobo that supports SLI connection, and also has two 3.0x16 PCIe slots.t. I want to get a ASUS Radeon HD 7850 so I can take advantage of the two 3.0x16 PCIe's, but as I add more monitors I would like to get another HD 7850. Even though these graphics cards are AMD would I still be able to use a SLI cable to connect the two Graphics Cards. If I cant use the SLI then how can I connect them?
 
You will need to use a Crossfire cable and run the cards in Crossfire mode. SLI is proprietary to Nvidia cards and the connector cables are different.

For me, the SLI cable came with my motherboard accessories, but I hear that Crossfire cables also commonly come bundled with your video card.
 

Dmdally

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does the mobo have to specifically support Crossfire because as far as I know mine only supports SLI which is weird because it has two 3.0x16 PCI-e Slots but Nvidia doesn't really make Cards using that kind of PCIe slot.
 

Yes, it does need to support Crossfire, but I would be shocked if it supported SLI and not Crossfire. In fact, I don't think a board like that exists.

You are in luck, according to the on-line documentation, your board supports Crossfire.
http://www.asus.com/Motherboards/Intel_Socket_1155/Maximus_V_GENE/

Now you just have to hope that AMD does a better job on their Crossfire driver support and you will be good to go.
http://www.hardocp.com/article/2012/01/17/amd_crossfirex_drivers_opportunity_lost
 

Dmdally

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Yeah thats what surprised me, the mobo is a ASUS Maximus V Gene and it has 3.0 PCIe slots but comes with a SLI cable. someone told me that a PCIe 3.0 is backwards compatible with a PCIe 2.0. Is this true?
 
Those driver problems were with the 7900 cards when bot Eyefinity and Crossfire were in use at the same time, I don't know if the 7800 cards share the same problems right now and to be honest, I don't think so. Also, that link is four months old. It's problems have been resolved (actually, they were fixed more than two months ago).
 

randomkid

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It is normal for motherboard suppliers to include SLI or CF cable in their bundle. Graphics cards also normally have a CF bridge (for AMD) or SLI bridge (for nVidia) although not always. But motherboard provided bridges are better because the length is sure to fit the PCIe gap.
If you still want to go for CF & your motherboard does not provide the CF bridge, just check if the graphics card you are buying have the CF bridge in the bundle that is long enough to fit your motherboard PCIe slots gap.

 

Dmdally

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Yeah IK the other one was on a slightly different subject and the only reason I asked on the other thread is because I thought that the other guy could give me a quick answer. sry bout that, I probably should have just left it on this thread, I was just really confused about the whole concept but thanks to you guys I get it now.