SLI Problems

[laseragna]

Got a second GTX 970 today and I cannot get SLI to work at all. Originally I put the new card in the 3rd PCI slot on my motherboard(which it designated in the manual). Both cards were detected but when I opened up the Nvidia control panel I could not enable SLI. They are bridged correctly. I have tried uninstalling the driver and then reinstalling it(although I'm not sure if it really reinstalled or it just "redetected" the driver or something since after a reboot the screen flickered and GeForce Experience showed up in the taskbar and had my last driver installed after a bit. I might retry that).

 

Specs are:

ASRock Z97M OC Formula

i5 4460

2x Zotac GTX 970(the "base" models, they have the same PIN and SKU since I've read that Zotac cards can be picky, I did buy my first 970 about 10 months ago, so hopefully they're not different revisions or something)

Thermaltake 650w Smart Series

Seagate 1TB SSHD

WD 2TB Blue

8 GB memory

 

I tried switching the cards around and that caused my old card, which was now in the third slot, to not be detected. Although the new card did work by itself just fine. I think I'll be ordering a replacement bridge just in case it is that just to cover that base. Any way this is possibly from the power supply? I've used the online calculators and I should have 50-80 watts to spare from the recommended power rating. Is there anything else I'm missing to help troubleshoot this?

[-rascal-]

SLI has a software limitation where the PCI-E slots are required to be at least X8 electrically.

 

Your very last PCI-E X16 slot is X16 in physical size, BUT it is only X4 electrically.

You need to use the first and second yellow-coloured PCI-E X16 slots, or else SLI will not work.

 

 

Also, make sure you connect all your display(s) to the primary card -- e.g. the top graphics card.

[laseragna]

That is the one I'm using. I should have clarified this better but I'm using the 3rd PCI slot which is the second PCI-E slot on the motherboard. Sorry if that isn't the most common way to refer to it, but it was just how the manual had worded it. I noticed that the manual said that the speeds needed to be 8x on both slots with SLI instead of 16x with a single card. Would it do it automatically or is there a setting in the BIOS/UEFI that can change that? I had a look and I could only find a way to change the speed by generation and I didn't know how that really worked as far as generation goes. Right now that setting is set to auto. Thanks for your help.

[-rascal-]

That is the one I'm using. I should have clarified this better but I'm using the 3rd PCI slot which is the second PCI-E slot on the motherboard. Sorry if that isn't the most common way to refer to it, but it was just how the manual had worded it. I noticed that the manual said that the speeds needed to be 8x on both slots with SLI instead of 16x with a single card. Would it do it automatically or is there a setting in the BIOS/UEFI that can change that? I had a look and I could only find a way to change the speed by generation and I didn't know how that really worked as far as generation goes. Right now that setting is set to auto. Thanks for your help.

 

Oh okay, that is correct then.

 

The motherboard BIOS should automatically make the necessary changes tot eh PCI-E slots when multiple graphics cards are installed, but it doesn't hurt to make sure.

 

My next BIG question. How many PCI-E 6/8 pin power connections do each of your GTX 970's need?

If I am looking at the right Power Supply, your Thermaltake unit only has two PCI-E 6+2 pin power connections.

 

If your GTX 970's has two PCI-E 6 pin connectors on it, it is mandatory to have all two connected.

Not none, and not one. Both.

[laseragna]

Each card needs two 6-pin power connectors. I'm using two molex to PCI-E power adapters(came with the graphics card) for the second card. Each adapter needs two molex power connectors to power it, which takes up all four of my molex connectors from my PSU.

[laseragna]

Just inspected my motherboard more closely and noticed these contacts(?) sticking out of the second card's slot. Maybe this is the culprit? I like to think I handle things pretty lightly but I'm not quite sure how this happened, I haven't used this slot at all before today. I looked at the graphics cards and both of them appear completely damage free as far as the contacts go.