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Your opinion on 2 x 980Ti versus 4 x 970

TinjawTinjaw Posts: 50
in Technical Help (nuts n bolts)

I am thinking about spending my tax refund on a new 3D workstation. I was wondering which configuration would be better for rendering. Should I buy two Nvidia 980Ti cards or four Nvidia 970 cards?

Comments

  • nicsttnicstt Posts: 11,715
    Tinjaw said:

    I am thinking about spending my tax refund on a new 3D workstation. I was wondering which configuration would be better for rendering. Should I buy two Nvidia 980Ti cards or four Nvidia 970 cards?

    Neither; wait for pascal.

  • Richard HaseltineRichard Haseltine Posts: 100,833

    How big are your scenes? Each card uses only its own RAM, so the two 980Tis woulkd handle larger scenes than the four 970s. Though if you can wait it may be worth doing as nicstt says - on the other hand, there's always something better in the offing.

  • TinjawTinjaw Posts: 50

    Hmm. A Google search says that Pascal cards are probably going to be out by April. With the increase in performance, it might just be the best option. Then again 980s and 970s should drop in price in anticipation of Pascal's release.

    Good point on the per card RAM limitation.

  • TinjawTinjaw Posts: 50
    Richard Haseltine said:

    How big are your scenes? Each card uses only its own RAM, so the two 980Tis woulkd handle larger scenes than the four 970s.

    You got me thinking. I've only ever looked at what GPU-Z says when I have a scene loaded. What is the best way to determine the size of a scene?

  • fastbike1fastbike1 Posts: 4,077

    As far as I know, something like gpu-z is the only way.

  • JCThomasJCThomas Posts: 254

    The two 980 tis will also give you room to add up to two more in the same system. Which ever you end up going with, you should get the reference cooler. The custom coolers from most video card manufacturers dump hot air into the case, whereas the reference cooler exhaust air out the back. Two 980 tis with custom cooling and 4 or 5 PCIE slots between them will be fine, but that would limit the upgrade down the road. 4 custom-cooled 970s (such as ASUS Strix or EVGA ACX) will cook each other.  If you have side exhaust fans on your case, then this point would be less valid but I've found that side intake with reference coolers yields better temps than side exhaust with custom cooling.

    The same things will probably hold true for Pascal when they come out.

  • bueller1998_df4ca4b697bueller1998_df4ca4b697 Posts: 161

    Why couldn't someone have posted this when I asked for card advice over the holidays, lol? I just installed my Titan Z yesterday. Had no idea we were in for that big of a drop so soon.

    BTW With a Z and my 970 I am still having some 2 hour renders. Some renders are going 10-30 minutes. But HDRI backgrounds, 3 lights with 3 characters, mirrors are taking quite a while. Been using the setup less than 24 hours, and about 8 rendering hours, so hopefully will cut some of that time down. RIght now I am just seeing what it will do.

    That being said, the IRAY light bouncing can be irritating.

  • mjc1016mjc1016 Posts: 15,001
    bueller1998_df4ca4b697 said:

    BTW With a Z and my 970 I am still having some 2 hour renders. Some renders are going 10-30 minutes. But HDRI backgrounds, 3 lights with 3 characters, mirrors are taking quite a while.

    Are you sure you haven't dropped to CPU mode?

    You can eat up a lot of video card memory with huge bacdrops.  Yeah, a Z has a lot of memory, but it is still a 'hard limit'. Especially if it is the only card in the system, because you are needing some of its memory for running the monitor/desktop, too.

    Mirrors will increase render times all by themselves.

  • bueller1998_df4ca4b697bueller1998_df4ca4b697 Posts: 161
    edited January 2016

    Is there a way to tell when you have exceeded the card's memory and dropped to CPU mode? All boxes are checked in render settings.

    Z seems to show as two 6-mb cards and then I have my 4mb 970. I doubt I am exceeding the memory with these 3 character scenes. I contacted tech support and the limits on a 4mb scene are 4 characters, 4 hairs, clothes, and a scene. Of course there are some variances but tech support said G3 was what they based it on roughly. The Titan Z appears to be 2 6mb cards and I have 4 mb card and I really doubt I am exceending any in the particular test scenes I'm trying.

    That being said, I have had the card home 24 hours at this point, so I haven't had much time to mess with it. 

    But I have a feeling with the infinite light bouncing of IRAY, I am going to have to mitigate my light and hair and glossy stuff even with a Titan Z and a 970.

    So I'm testing and posting as a warning, but again, I'm a day into it, with work and sleep taking up 2/3 of that.

    Please let me know if you can tell when the renders convert back into CPU mode due to scene memory overload.

    Post edited by bueller1998_df4ca4b697 on
  • mjc1016mjc1016 Posts: 15,001

    The 970 will drop out when 4 GB is reached (probably a bit sooner, if that is what your monitor is hooked up to).  The Z will drop at 6 GB.

    Now depending on the size of your HDR backdrop you could be hitting 4 GB with just 3 figures.  Iray uses 3 bytes/pixels for image files and a large HDR can eat up a few hundred MBs. That scene size from support also assumes leaving Iray's texture compression at default values and/or 'average' 4K texture maps for the characters, also without many HD morphs or other high subdivision usage.

    GPU-Z is one of the tools often recommended for monitoring memory consumption.  You can also check the log file (Help > Troubleshooting > View Log).

     

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