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Rendering Speed - GPU vs GPU + CPU

tkztkz Posts: 149
in The Commons

I recently upgraded my 960 to a 1080 ti... and I have a i7 6700k (currently not OC'd for the summer heat...) with 32GB of 2800 Ram on OSX.

I am working on a set of about 250 renders... and recently stopped using the combo of CPU + GPU as my evo 212 gets too loud... I was quite suprirsed that removing the CPU didn't slow down the renders that much...

Out of curiousity, I did some more tests...  on a render that takes 26 mins with just the gpu, adding the CPU only shaved about 1.5-2 minutes off the render time...

Is this normal? 

(Air flow in the case is pretty solid... GPU stays 10C below it's throttle speed @ 74C, and CPU isn't even hitting 60C with the OC off.)

Thanks!

Tom

Comments

  • JamesJABJamesJAB Posts: 1,766

    Yes, Iray is designed for Nvidia GPU rendering.  CPUs are not designed to do that kind of number crunching.
    So, yes with very fast GPUs, adding the CPU in is a negligable boost, and on some systems it actualy slows down the render.

  • tkztkz Posts: 149

    Thank you for confirming James...

    I was somewhat aware of that... but didn't realize that a 6700k was that weak in compairson. 

    I think my perception must have been distorted by using a 960 with much lower quality settings.... 

     

  • Leonides02Leonides02 Posts: 1,379

    CPU isn't worth it at all, especially if you're using your computer for other things.

  • MattymanxMattymanx Posts: 6,996

    My hardware is very close to the OPs but a windows PC instead.  I did a test last year when I got the new system.  What took my CPU 1 hour by itself, took my dual 980TIs 3 min.  So there is no point in including the CPU, you gain nothing.

     

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