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Dual GPU render efficiency?

NamelessxPeasantNamelessxPeasant Posts: 11
in Technical Help (nuts n bolts)

Recently I got my self a rtx 3090, while enjoying the power of technology, since Iray support multi graphic cards render, I wonder should I put my old rtx 2060 on work too? since squeeze another card inside computer will make more heat problem, and also mean extra burden for power.

So how does dual GPU work in daz? will it double the render speed, or just a small boost? did it even worth a try?

Comments

  • GordigGordig Posts: 9,892

    Consult this thread for comparisons between different combinations of cards. Your particular combination may or may not already be represented.

  • fred9803fred9803 Posts: 1,562

    If you had two 3090s LOL you could sinc them with an RTX NVLINK Bridge and then you'd be really cooking with gas. Alternatively, seeing as your probably broke from buying just one of these overpriced beasts, you could dedicate the 2060 to your monitor and let the lone 3090 just do it's stuff with rendering. I was dead set on a 3090 until I threw in my job last year and now I'm watching my pennies very closely.

  • GordigGordig Posts: 9,892

    You should also be aware that Iray will only use a GPU if the entire scene fits onto the card. What this means for you is that if your scene uses less than 6GB (or 8GB, depending on whether your 2060 is a Super or not), then both cards will be utilized; if it's greater than 6/8GB but less than 24GB, only the 3090 will be used; and if it's greater than 24GB, neither card will be used.

  • StonemasonStonemason Posts: 1,177

    I'm running two 3090's and two TitanX's, the promos I do tend to take about a minute or two each,rendered at double the promo resolution.

    it does get really hot though,when batch rendering it seems to overheat after the 3rd or 4th render and the system shuts down.

  • fred9803fred9803 Posts: 1,562
    edited July 2021

    You'd probably need a liquid cooler setup on all those GPUs if you haven't got them. Something like these for the 3090s if they fit and of cause a CPU one too. And you're lucky NZ didn't get that hot over there like Oz.

    Post edited by fred9803 on
  • MattymanxMattymanx Posts: 6,898

    fred9803 said:

    If you had two 3090s LOL you could sinc them with an RTX NVLINK Bridge and then you'd be really cooking with gas.

    The way Iray works with multiple cards is that it loads the scene on each, renders and compiles all of them into a single image for you.   So Iray does not require the cards to be linked together and in fact, they have always recommend that you do not have SLI enabled when rendering.

    As for the bennefits to mutiple cards, if they are identical then you will see render times be cut in half, I have seen this myself with my 980TIs.  Not sure about 3 or 4 cards that are the same.  As for using different cards together, millage will vary.

  • MattymanxMattymanx Posts: 6,898
    edited July 2021

    Stonemason said:

    I'm running two 3090's and two TitanX's, the promos I do tend to take about a minute or two each,rendered at double the promo resolution.

    it does get really hot though,when batch rendering it seems to overheat after the 3rd or 4th render and the system shuts down.

    I would guess that all 4 cards are back-to-back and taking in heat from one another.  I had that problem when I first got my computer in 2016.  Thankfully I somehow killed the secondary PCI-E slot and was forced to move my second video card to the third slot.  Performance was not hindered and my temp on the primary card dropped from 83C down to 70C at full speed.

    Post edited by Mattymanx on
  • PerttiAPerttiA Posts: 10,014

    Mattymanx said:

    fred9803 said:

    If you had two 3090s LOL you could sinc them with an RTX NVLINK Bridge and then you'd be really cooking with gas.

    The way Iray works with multiple cards is that it loads the scene on each, renders and compiles all of them into a single image for you.   So Iray does not require the cards to be linked together and in fact, they have always recommend that you do not have SLI enabled when rendering.

    As for the bennefits to mutiple cards, if they are identical then you will see render times be cut in half, I have seen this myself with my 980TIs.  Not sure about 3 or 4 cards that are the same.  As for using different cards together, millage will vary.

    NVLINK is different from SLI, with NVLINK the VRAM on identical cards is shared (for textures), which would allow you to render larger scenes without dropping to CPU - Too bad they put the NVLINK connectors only on 3090 on the 30xx series. The 20xx series has it on 2080 and 2070 super.

  • NamelessxPeasantNamelessxPeasant Posts: 11

    Thanks! I guess I'll stick with single GPU for nowsmiley, don't want push my lovely card too hard.

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