2x GTX 980 nvidia / motherboard SLI

anneghostghost

Hi,

I have just purchased a new pc with 1x GTX 980 to use daz3d iray. My motherboard doesn't support SLI though but I would like to purchase another GTX 980. Is there a way to use both nvidia's maybe if they run at x8? or would be a better option to buy a single card like TITAN X in future and replace the gtx 980?

my motherboard :

- 1 x slot PCI Express x16, running x16 (PCIEX16) 
- 1 x slot PCI Express x16, running x4 (PCIEX4) 
- 2 slots PCI Express x1 

 

mjc1016

Iray doesn't use SLI, so it doesn't matter if they motherboard supports it.

And while slower, for rendering having 2 'half speed'  instead of 2 'full speed' slots (8 vs 16) isn't as critical as it is for gaming.  It isn't THAT much slower (a couple of seconds on a multi-minute render).  Large complex operations that spend a lot of time in a 'static' state don't benefit much from faster bus speeds.

anneghostghost

mjc1016 said:

Iray doesn't use SLI, so it doesn't matter if they motherboard supports it.

And while slower, for rendering having 2 'half speed'  instead of 2 'full speed' slots (8 vs 16) isn't as critical as it is for gaming.  It isn't THAT much slower (a couple of seconds on a multi-minute render).  Large complex operations that spend a lot of time in a 'static' state don't benefit much from faster bus speeds.

Really? oh I didn't know iray doesn't use SLI, thank you!

mjc1016

Yeah, Nvidia even says to disable SLI when using Iray. 

Silver Dolphin

MJC is correct what is more important is Cuda cores and Video ram the more core the faster the render. The more Video memory the larger the scene you can render. If you only have 4 gig of video ram do compositing (Render in parts and then layer them together in PS or GIMP)

oomu

I confirm too: no need for SLI. You can even use three or more GPU with mostly linear improvement in rendering time. Bus speed (x16, x8..) does not matter that much for iray rendering.

 

What you want is Video memory, for each GPU. The more you have, the more you will be able to render very complex scenes.

two 980 ( 2 x 2048 cores) should be better than one titan X (3072 cores,  but titan X is sold with 12GB of vram... it's quite enough for mostly whatever you would do in DAZ)

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I don't know if you can mix one 980 and one Titan X without instability and random crash. Nvidia advises to only use exactly same cards. But two cards from same generation should work in theory.