Cannot enable SLI?

[Nevakonaza]

Hey guys,

Have 2 GTX 970s on a Z77X-UD3H motherboard.

• GPU 1 - Galax GTX 970 EXOC Black Edition
• GPU 2 - KFA2 GTX 970 EXOC infin8 Black edition

Both have 4GB of Vram,They're essentially the same card on the outside just rebranded Galax-KFA2 .

Im having an issue enabling SLI,The option to enable it is greyed out,i have connected 2x hard pcb sli bridges to the card

Now ive looked on GPUZ and both cards have different BIOS numbers,which i expected as they're slightly different clocked cards i think,Do you guys think it could be a BIOS issue?
where do i even find the latest bios for these cards as i see no option on both of their websites to download the latest bios?

Of course im going to try reseating the cards,reseating the sli bridges,try only one sli bridge,check mobo bios is latest etc,but going to have to do that tomorrow now,just wondering if any of you guys had any more ideas or experienced this before.

cheers.

 

[Rroff]

Do you have the cards in the right PCI-e x16 slots - most of those boards only support SLI using 2 of the slots and often not the two slots you'd think/most convenient also if you are using additional PCI-e devices sometimes that can knock it out.

 

[stooeh]

Well SLI requires minimum PCIE X8 slots so I would make sure the slots you are using are at least that. Also could be a 970 specific issue where certain 970s won't SLI with other non identical ones.

 

[Rroff]

From the manual it looks like the first (nearest CPU) and 2nd full size slots on that board are the x16 and x8 and the last one x4 - but I'd assume from the layout/spacing OP is probably using 1st and 2nd anyhow.

 

[Dempsey22]

I remember reading before that certain combinations of 970s won't SLI at all. I don't know if it was fixed with driver or bios updates though.

 

[Quartz]

Im having an issue enabling SLI,The option to enable it is greyed out,i have connected 2x hard pcb sli bridges to the card

You should only have one SLI bridge installed.

 

[andicole0]

There should not be a problem with different 970's. Do they both show up in device manager? You may have a power issue as 650W is really the minimum for your setup. It might not be able to supply the necessary current for both GPU's.
You only need one SLI bridge even though the cards have two edge connectors, that is for potential tri-sli and connecting to a 3rd card.
Andi.

 

[Radox-0]

I remember reading before that certain combinations of 970s won't SLI at all. I don't know if it was fixed with driver or bios updates though.

Was with certain EVGA models AFAIK: https://www.evga.com/support/faq/afmviewfaq.aspx?faqid=59534

Was done at bios level and not chnaged, but was not an issue for other manufacture models I believe. I think EVGA went down a weird restriction route for only there 970's for some reason.

 

[stooeh]

There should not be a problem with different 970's.

Certainly shouldn't be but there was an issue as mentioned above. It did affect other 970s but afaik only EVGA acknowledged it (presumably because they had it affecting people with only EVGA cards). I couldn't get SLI to work with a Inno3d 970 and neither a Galax nor Palit 970 though they all worked with the same brand card fine. For me it manifested in requesting that an SLI bridge be connected even though it was present. There was some hack that connects SLI over PCIE bus only and that worked...

 

[Nevakonaza]

Thanks for all replies folks,Well its wierd i taken off one SLI connector as i had both connected,then after i restarted and windows downloaded an update and installed it,Now i can enable SLI.

Single 970

SLI 970

3D MARK Single

3D MARK SLI

 

[Quartz]

Well its wierd i taken off one SLI connector

I'm glad my answer fixed it for you but it's not weird at all: the second SLI connector is for when you are using 3 way or 4 way SLI.

 

[andicole0]

I'm glad my answer fixed it for you but it's not weird at all: the second SLI connector is for when you are using 3 way or 4 way SLI.

Odd though as Nvidia say the second bridge will do nothing and won't upset the function. In fact some people have used 2 for aesthetic reasons. OP did also download an update?!
Andi.

 

[Nevakonaza]

I'm glad my answer fixed it for you but it's not weird at all: the second SLI connector is for when you are using 3 way or 4 way SLI.

Well removing the second sli bridge and restarting the pc seems to have triggered windows to download an update then bam,option to enable SLI was there

Just wondering,in games is it only able to make use of 4GB of vram or both the 4gb combined so 8GB?..because i noticed in GTA V it shows using just over 4gb of vram of 8 available?

 

[andicole0]

SLI will only use the memory available on one card but duplicates it on the other. I think Crossfire uses both together but I could be wrong there.
Andi.

 

[Shiari]

SLI will only use the memory available on one card but duplicates it on the other. I think Crossfire uses both together but I could be wrong there.
Andi.

No, you're wrong there. Each card (in either SLI or CF) needs a copy of everything in its own VRAM, in SLI and CF you only have as much VRAM available as the card with the lowest amount of VRAM has. If you had a 4GB and 8GB card together, you'd effectively have 4GB of VRAM.

 

[andicole0]

No, you're wrong there. Each card (in either SLI or CF) needs a copy of everything in its own VRAM, in SLI and CF you only have as much VRAM available as the card with the lowest amount of VRAM has. If you had a 4GB and 8GB card together, you'd effectively have 4GB of VRAM.

So not completely wrong! In fact correct as far as the 970's are concerned
Andi.

 

[Smffy]

So not completely wrong! In fact correct as far as the 970's are concerned
Andi.

Key thing for OP to note though isn’t it, adding another 970 won’t suddenly render your settings better on newer titles where you effectively still have 4GB VRAM...