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Question about 16x/8x SLI and rendering/gaming

SnowSultanSnowSultan Posts: 3,773
in The Commons

I'm considering a motherboard that has two 16x PCI video card slots, but someone commented that you need at least an Intel i7-5830K to be able to run both cards in SLI at 16x. I have two questions about this:

- Is that guy right? Can you not run two cards in SLI at 16x if you have an i7-5820K?

- Is there any real difference in rendering speed, Iray live-previewing, or gaming if one card runs at 16x and the other at 8x? I read some articles that said there is virtually no difference in gaming performance, but they were quite old and high end cards like the 980ti and the Titan were not available at the time. I have not found anything regarding this and rendering except a discussion in an Octane forum that said they didn't seem to notice much difference.

Thanks in advance for any advice.

Comments

  • mjc1016mjc1016 Posts: 15,001

    Well, since Iray doesn't 'do' SLI, anything dealing with SLI doesn't apply.

    Iray will use any/all cards that it can, without needing SLI.  Also since for the most part, what is going to and happening on the card during a render is not 'moving' (even animation frames), there won't be much, if any noticeable speed changes without SLI.   For a game, each frame is a fraction of a second...for a render, it is several seconds to hours.

  • SnowSultanSnowSultan Posts: 3,773

    You're right, I blanked out and forgot that Iray doesn't take advantage of SLI. Been very forgetful lately, I'm having to make notes to remember a lot of the 3D stuff I do these days. I'm still a little curious about needing the 5830 to use 16x/16x for gaming SLI because it's $300 more than the 5820, but I highly doubt it's worth it.

  • mjc1016mjc1016 Posts: 15,001
    SnowSultan said:

    You're right, I blanked out and forgot that Iray doesn't take advantage of SLI. Been very forgetful lately, I'm having to make notes to remember a lot of the 3D stuff I do these days. I'm still a little curious about needing the 5830 to use 16x/16x for gaming SLI because it's $300 more than the 5820, but I highly doubt it's worth it.

    I haven't been paying much attention to the I7 requirements/features so I can't say for sure.

  • prixatprixat Posts: 1,616
    edited January 2016
    SnowSultan said:

    You're right, I blanked out and forgot that Iray doesn't take advantage of SLI. Been very forgetful lately, I'm having to make notes to remember a lot of the 3D stuff I do these days. I'm still a little curious about needing the 5830 to use 16x/16x for gaming SLI because it's $300 more than the 5820, but I highly doubt it's worth it.

    He must be talking about the overall number of PCIe lanes on each chip.

    The 5820 is a cut down model with 28 lanes. The rest of the X99 family have the full 40 lanes. 

    On the 5820, the cards will balance down to 8x/8x. In practice, 8x is more than enough for a GPU, (actually I don't know of anything that uses the huge capacities of 16x. Maybe professional sound cards get close.)

    The real limit is maximum number of GPUs: Three (8x/8x/8x) on the 5820 and four (8x/8x/8x/8x) on the rest.
    ...for our purposes, you can only put three TitanX cards on the 5820! frown

    Post edited by prixat on
  • SnowSultanSnowSultan Posts: 3,773

    That is what he mentioned, the PCIe lanes. Thanks for confirming all of that.  :)   He did say that two cards would run in 16x/8x though. 

    Haha, I don't think I have to worry about needing (much less being able to afford) more than three video cards of any kind any time soon.   :D

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