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Secondary GPU not detected

Luciel
Level 7
Hi Guys,

Mobo: Maximus V Formula

So I have 2 GTX 560 Ti which work fine in SLI on this mobo.

Recently however I took them out and installed a 580 (just 1), the why is not important, what´s important is that when I add a second card for physics (I´ve tried 4 cards I know work in either the second or third pci-e ports) they are not detected in the BIOS or in Windows.

So out of curiosity I take the 580 out, put my 560 ti SLI back in and works fine, I know all cards work fine, I know the PCI ports work fine, so I´m a bit lost here, am I missing something? Why doesn´t this work?

Thanks.
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14 REPLIES 14

HiVizMan
Level 40
Once you put the second card in do you do a nVidea driver install? And is the card picked up in the nVid control panel?
To help us help you - please provide as much information about your system and the problem as possible.

Myk_SilentShado
Level 15
Boot up in SLI Mode, get into Windows, disable SLI. Power down, remove the 2nd 560 and insert the 580. Boot up and hopefully get a successful POST and boot 🙂

Luciel
Level 7
HiVizman & Myk Silentshadow,

Before removing the 2 560 ti I uninstalled nvidia drivers, shut down the pc, take them out put the 580 and the secondary gpu in (also tried later on just the 580), boot up windows, installed nvidia drivers and only the 580 is detected (bios only sees the card on pci-e 1 as well, doesn´t see the other card). If I uninstall the drivers yet again, take out the cards, put the 2 560 ti in, they are both detected. I even tried these 560 ti as secondary cards, knowing first hand they worked, but same result, nada.

PS: Just to be clear that not booting/post has never been the issue, just the fact of the mobo not detecting the secondary cards when not using 2 of the same.

PS2: Just tried flashing BIOS, no difference.
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HiVizMan
Level 40
And this is the case in the nVidia control panel too?
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Luciel
Level 7
That is correct.
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HiVizMan
Level 40
That is simple confounding.

Two cards are seen in SLi.

But swap out the top 560 for the 580 and the second card is not seen.

I have no logical answer as to what is going on or why. I have attempted to duplicate this on my test bench with three cards and I had not problems.

How many power connectors are needed in total for the sli configuration and the 580 plus 560 set up.

Could it be that a power cable is not working when you have the 580 connected? And yes I know I am clutching straws here.
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Luciel
Level 7
Well, the GTX 560 Ti requires 2x6 pin each, the 580 requires 1x8+1x6pin. I´ve tried swapping them round, no joy.

This is far the weirdest issue I´ve ever had with hardware, just has no logical answer o.O
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HiVizMan
Level 40
I agree odd.

I seem to recall about a year ago now, someone had a similar issue with physics card not being picked up (not quite the same as your issue mind you) but it was a simple fix, in his case he was putting the SLi bridge on both of the videocards, the main one and card which he wanted to have as a physix card.

Are you able to get any two cards picked up by the bios or GPUz regardless of what order you put them in?
To help us help you - please provide as much information about your system and the problem as possible.

Luciel
Level 7
No SLI bridge here between non equal cards 😕

When it´s both of the 560, yes, no issue, when it´s any other combination of cards, no.

Remember the BIOS doesn´t even see a second card in the GPU section (where it reports what ports are occupied and at what speeds they run.

The weirder thing is that even if the bios doesn´t detect it, it will run the first card at 8x when there´s another one in so I imagine it must know at some level there´s a card there or it wouldn´t split the bandwith.

I really don´t want to have to RMA this, I´ve gone through 3 asus RMAs in the last year with different computers, just not a happy bunny right now V_V
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