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Iray render with CPU and GPU .. is CPU worth it?

Sparkie ShockSparkie Shock Posts: 96
in Daz Studio Discussion

I have a PC system for rendering DAZ iray stuff that has a spec of:

i7 4790 (4 core) 3.4ghz

32 gigs of DDR 3 ram at 1333mhz

And a Titan X (2nd gen with 12 gigs vram and 3072 cuda cores.

 

Usually I render with both CPU and GPU ticked but tonight I decided to see how fast it would render with only the GPU.

typically the scenes I render are fine to 10,000 iterations, which take roughly 3 hours and 30 mins. Lots of light sources, emissive properties and depth of field (stuff that slows down render).

wirh the CPU turned off it seems that in 3 hours and 45 mins It could do 12,300 iterations. So it would seem that the CPU actually hampers rendering if you have an nvidia card that can handle the scene. I'm guessing with CPU enabled for render it makes giving priority to the CPU?

I was just wondering if anyone else had found this if you have a high end graphics card.

I absolutely recommend the Titan X for rendering. I have two of those now, first one I bought new, the second I got from a guy on Craigslist for s lot less than I paid new. ($1700 for new, $680 second hand). There is a newer version of Titan X being released now so if you're waiting for the right moment .. get yourself a Titan X (pascal version).

Anyways, curious to know if anyone else has found the CPU to slow things down during iray render?

 

Comments

  • MattymanxMattymanx Posts: 6,955

    I did a test scene that took 50min on the CPU alone and only 3 min on my 980TIs.  The CPU is not going to add enough of a speed boost.  Might as well leave it out.  I find I can still work in other programs a bit while iray renders if I leave teh CPU out.

  • Sparkie ShockSparkie Shock Posts: 96

    Yes it's odd. One would expect the CPU to add some help to the render. But my findings is that it actually slows it down a little. Obviously this is all dependent on your system spec, graphics card and the scene one is rendering. But for my spec and the kind of work I'm doing it's definitely an advsntshe to leave the CPU out of this.

    At least I'll be able to watch a DVD while my renders bake ????

  • DustRiderDustRider Posts: 2,800

    Tour findings are correct. On most systems using both CPU and GPU will slow rendeing down a bit.

  • TheKDTheKD Posts: 2,703

    Can confirm, CPU slows me down, although my CPU is only i5 2500(not 2500k lol). Maybe if you have a nice newer CPU it would be worth it.

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