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Questions about PCI lanes (x4 vs x8 x16).

bshugs@hotmail.combshugs@hotmail.com Posts: 176
in Technical Help (nuts n bolts)

I'm looking at my next build and I'm looking for some info and practical advice.  Currently I'm running an i7 (LGA 1150 socket) with a 1080 and 1060.  I'm trying to weight the cost/benefit of the three main PC paths:  AMD Threadripper, AMD Ryzen, and Intel i7 (1151 socket).  I like the extra RAM and PCIe lanes Threadripper provides, but the cost is pretty high.  The other two both offer 64GB of RAM at a lower cost but with fewer PCIe lanes.  I am a hobbiest, so the system has to work as a general-use/gaming PC also.  So, my two main questions regarding PCIe are:

What effect is there on iRay render performance if the card is running in x4 or x8 mode instead of the full x16?

Can mining rig equipment be used effectively for iRay renders?  Specifically, equipment that has one or more cards connecting through a PICe x1 slot in order to allow additional cards.  (Examples : Newegg.com, and Amazon.com )

Thanks for any help.

Comments

  • JamesJABJamesJAB Posts: 1,760

    In Iray the only thing PCI-e lanes are used for is transfering the scene into VRAM for rendering, and sending itteration updates out to the system. (1x PCI-e mode should work fine)
    The rendering process takes place entirely inside the video card, so yes as long as your mining rig is equipped with Nvidia GPUs (GTX 6XX or newer) with enough VRAM to fit the scene they should all help in the rendering job.

  • KitsumoKitsumo Posts: 1,216
    edited May 2019
    Windamyre said:

    What effect is there on iRay render performance if the card is running in x4 or x8 mode instead of the full x16?

    Not much. The render takes a second or two longer to start, but having an extra card more than makes up for it.

    https://www.daz3d.com/forums/discussion/175226/effects-of-pci-e-bandwidth-on-load-and-render-times

    Edit: I'm not sure what type of scene that guy was rendering to get 10-13 second slowdowns. Mine was barely more than a couple of seconds at most.

    Windamyre said:

    Can mining rig equipment be used effectively for iRay renders?  Specifically, equipment that has one or more cards connecting through a PICe x1 slot in order to allow additional cards.  (Examples : Newegg.com, and Amazon.com )

    Yes.

    Post edited by Kitsumo on
  • Da_green1977_aa156fc426Da_green1977_aa156fc426 Posts: 45
    edited May 2019

    So after reading this maybe I can, if I understand correct, swap my cards places?

    I put my rtx2080ti in my x16 slot and my gtx1080ti in my x4 slot. Problem is that the rtx card get really hot and clock down to around 1200Mhz. 

    The air ventilation is better around my x4 slot.

    BR // Daniel

    Post edited by Da_green1977_aa156fc426 on
  • kenshaw011267kenshaw011267 Posts: 3,805

    You need to increase airflow in your case. I recently picked up a 2070 and am running it with my old 1080ti. Both are running at standard boost speeds throughout renders.

    Check the fan curves for the GPU, CPU cooler and for the overall case, you'll need to go into the BIOS to set the CPU and case fan curves.

  • Da_green1977_aa156fc426Da_green1977_aa156fc426 Posts: 45

    Hello,

    Thanks,

    I will look at the possibility to increase the airflow,

    i have a small m-atx cube chassie and a m-atx motherboard. I think 2 more 120mm fan will fit in the chassi. 

     

    BR // Daniel

  • JamesJABJamesJAB Posts: 1,760
    edited May 2019
    Da_green1977_aa156fc426 said:

    Hello,

    Thanks,

    I will look at the possibility to increase the airflow,

    i have a small m-atx cube chassie and a m-atx motherboard. I think 2 more 120mm fan will fit in the chassi. 

     

    BR // Daniel

    For running 2x 250w graphics cards, I would reccomend getting a larger case, (and possibly a larger motherboard that has an extra slot between the 16x and 4x PCI-e slots)
    Also check your power supply because if either one of your GPUs (or both) are factory OC versions, they could easily be trying to use between 300 and 350W each.  This could be causing throttling issues if the PSU cant put out enough juice.

    In your current setup here are my recomendations :
    1. place the GTX 1080 ti into the 16x slot and have it run your display.
    2. place the RTX 2080 ti into the 4x slot for better airflow durring renders
    3. Go into your "Nvidia Control Panel" - "3D Settings" - "Configure Surround, PhysX" and set your PhysX processor to the RTX 2080 ti and check the box for "Dedicate to PhysX"
         This will lower the VRAM usage and set the GPU to 0% usage when not rendering. (this will also have a lowering effect on the GTX 1080 ti temperature outside of rendering)
    4. Set The RTX 2080 ti as the dForce device (More powerful and better air flow.)
    5. Remove the CPU checkmark from Iray devices for both "Photoreal" and "Interactive". (This will lower the overall temperature in your case.
    6. If there is room for more fans in your case add them, but make sure you are directing all of the airflow in one end and out the other.
     

    Post edited by JamesJAB on
  • bshugs@hotmail.combshugs@hotmail.com Posts: 176

    Wow.  Thank you to everyone who responded.  I had done a search of the forums for information, but managed to miss links above.

    I think I will be passing on Threadripper for the foreseeable future.  Though the thing is a beast, the cost savings would allow me to look into more GPU power.

  • Da_green1977_aa156fc426Da_green1977_aa156fc426 Posts: 45
    JamesJAB said:
    Da_green1977_aa156fc426 said:

    Hello,

    Thanks,

    I will look at the possibility to increase the airflow,

    i have a small m-atx cube chassie and a m-atx motherboard. I think 2 more 120mm fan will fit in the chassi. 

     

    BR // Daniel

    For running 2x 250w graphics cards, I would reccomend getting a larger case, (and possibly a larger motherboard that has an extra slot between the 16x and 4x PCI-e slots)
    Also check your power supply because if either one of your GPUs (or both) are factory OC versions, they could easily be trying to use between 300 and 350W each.  This could be causing throttling issues if the PSU cant put out enough juice.

    In your current setup here are my recomendations :
    1. place the GTX 1080 ti into the 16x slot and have it run your display.
    2. place the RTX 2080 ti into the 4x slot for better airflow durring renders
    3. Go into your "Nvidia Control Panel" - "3D Settings" - "Configure Surround, PhysX" and set your PhysX processor to the RTX 2080 ti and check the box for "Dedicate to PhysX"
         This will lower the VRAM usage and set the GPU to 0% usage when not rendering. (this will also have a lowering effect on the GTX 1080 ti temperature outside of rendering)
    4. Set The RTX 2080 ti as the dForce device (More powerful and better air flow.)
    5. Remove the CPU checkmark from Iray devices for both "Photoreal" and "Interactive". (This will lower the overall temperature in your case.
    6. If there is room for more fans in your case add them, but make sure you are directing all of the airflow in one end and out the other.
     

    Thanks for the nice recomendations, i will try to follow them as soon as i have time.

    my psu are at 850w with an i5 8400.

    BR // Daniel

  • Saxa -- SDSaxa -- SD Posts: 872
    JamesJAB said:
    1. place the GTX 1080 ti into the 16x slot and have it run your display.

    2. place the RTX 2080 ti into the 4x slot for better airflow durring renders

    Do you know how it works with the nvidia drivers in this setup? 

    Asking because Nvidia has 2 different versions to download:  (1) RTX Gen vs (2) Previous Gens.

    Might try your suggestion for putting the RTX2080Ti in a lower PCI slot.  But also wondering how that affects alternative uses, like gaming?

  • JamesJABJamesJAB Posts: 1,760
    Saxa -- SD said:
    JamesJAB said:
    1. place the GTX 1080 ti into the 16x slot and have it run your display.

    2. place the RTX 2080 ti into the 4x slot for better airflow durring renders

    Do you know how it works with the nvidia drivers in this setup? 

    Asking because Nvidia has 2 different versions to download:  (1) RTX Gen vs (2) Previous Gens.

    Might try your suggestion for putting the RTX2080Ti in a lower PCI slot.  But also wondering how that affects alternative uses, like gaming?

    If you will be using the computer for gaming, you will want the RTX 2080 ti in the PCI-e 16x slot and the monitor plugged into it.
    You can still set the GTX 1080 ti as a dedicated PhysX card so that it will not be making extra heat inside your computer while gaming unless the game is on the following list. (https://en.wikipedia.org/wiki/List_of_games_with_hardware-accelerated_PhysX_support)

  • Saxa -- SDSaxa -- SD Posts: 872

    Thanks!  Kinda guessed that was the case.  But ya never know with some surprising tricks out there for some things. 

     

  • kenshaw011267kenshaw011267 Posts: 3,805

    You definitely shouldn't be running dual GPU's in a mATX rig. There's just not enough of everything in one of those.

  • PadonePadone Posts: 3,796
    edited May 2019
    Windamyre said:

    Can mining rig equipment be used effectively for iRay renders?  Specifically, equipment that has one or more cards connecting through a PICe x1 slot in order to allow additional cards.

    Just one note that doesn't appear to be discussed before. If you also like to use other render engines other than iray, such as cycles or octane, then pcie lanes do matter for out of core rendering. That is, out of core requires 8x or 16x pcie to render fast. For "standard" rendering a mining rig with risers will do fine since the cards are feeded before rendering.

     

    Post edited by Padone on
  • Da_green1977_aa156fc426Da_green1977_aa156fc426 Posts: 45

    Hello,

    I did install a extra fan (120mm) and swap the two gpu cards. Now everything seems fine. Did a test render 3000*2500 for a hour and both cards was around 75C.

    BR// Daniel

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