SLI Primary/Secondary card problems

[voda528491]

I have two GTX 760's running in SLI together and am having a weird issue. I have a Gigabyte Windforce 3x OC 760, and a Zotaz reference 760. Both are the 2gb version, and both are bios modded, and I've made all the settings the same. I bought the zotac card off ebay for $50, because it was overheating. I replaced all the thermal paste, and that fixed the overheating issue. Then I discovered that it wouldn't output video. So I just put my Gigabyte one on the top slot to make it the primary card, and gave it the display cable. Recently, I found that my Zotac card is actually the primary card, and I have less performance because of this, as the Gigabyte card is the stronger card. The Zotac card shows all the signs of being primary, it has raised voltage, raised temperature, at load and idle, raised load, and raised power draw over the other, and yet it's on a lower pci slot. I've heard that the top card is always the master card, but that doesn't seem to be the case. I swapped the cards, and then nothing displays. I have a MSI 990FXA Gaming motherboard. What's the problem with my cards, and how can I make the Gigabyte card, on the top slot, the primary card?

 

[10tacle]

I had this issue when running two EVGA GTX 970s, one a reference cooler design, the other an ACX 2.0+ cooler design. Both were factory overclocked, but the ACX card was a little faster yet it was added as the second GPU. I had to delete the Nvidia drivers and move the ACX card to the first slot, then download the drivers to get that ACX card assigned as the first GPU. Then I shut down, added the second GPU, and it showed up as the second card. But I wound up selling that second reference GPU and got another ACX GPU.

Also note that even though Nvidia says all GPUs of the same type are SLI capable, that is not always the case. Especially with EVGA who use custom BIOSs between different models of the same GPU. My reference and ACX EVGA 970s were not supposed to work in SLI, but they did. However, the scaling was horrible (50% or less). Adding a second GPU of the exact same model put that scaling more in line to 80% or so.

 

[voda528491]

I had this issue when running two EVGA GTX 970s, one a reference cooler design, the other an ACX 2.0+ cooler design. Both were factory overclocked, but the ACX card was a little faster yet it was added as the second GPU. I had to delete the Nvidia drivers and move the ACX card to the first slot, then download the drivers to get that ACX card assigned as the first GPU. Then I shut down, added the second GPU, and it showed up as the second card. But I wound up selling that second reference GPU and got another ACX GPU.

Also note that even though Nvidia says all GPUs of the same type are SLI capable, that is not always the case. Especially with EVGA who use custom BIOSs between different models of the same GPU. My reference and ACX EVGA 970s were not supposed to work in SLI, but they did. However, the scaling was horrible (50% or less). Adding a second GPU of the exact same model put that scaling more in line to 80% or so.

So if I remove the Zotac card, reinstall the drivers, and then reinstall the Zotac card, it should work?

 

[10tacle]

So if I remove the Zotac card, reinstall the drivers, and then reinstall the Zotac card, it should work?

If you want your Gigabyte card as your primary card, put that in the first slot and take out the Zotac. Then download the latest drivers with only that Gigabyte GPU in the first slot. Then add the Zotac card in the second slot and the drivers should pick that up in SLI and assign it as the second GPU.

That's the way it worked for me anyway.

 

[voda528491]

So if I remove the Zotac card, reinstall the drivers, and then reinstall the Zotac card, it should work?

If you want your Gigabyte card as your primary card, put that in the first slot and take out the Zotac. Then download the latest drivers with only that Gigabyte GPU in the first slot. Then add the Zotac card in the second slot and the drivers should pick that up in SLI and assign it as the second GPU.

That's the way it worked for me anyway.

It worked! Thanks!

 

[10tacle]

Cool! My pain of dealing with it made your life easier....glad I could share my experience!