CPU or GPU in rendering?

nikijunpei81

Hi, my pc have a 11th Gen Intel(R) Core(TM) i5-11300H @ 3.10GHz   3.11 GHz, and a Windows  11 OS. Ma Graphic Card ia a Nvidia GeForce RTX  ti.

In render setting, by default, in advanced, i see that both CPU and GPU is selected. This is my new pc, and in the old pc i saw only the GPU selectable.

What i have to to: use only Nvidia, or both for iray rendering? I read on Rendeguide that both could be not always the good solution.

Thank you for your patience.

nakamuram002

I use both, with no problem.  What kind of Nvidia GeForce RTX ti do you have - 3060, 3070, 3080, or 3090?

Richard Haseltine

Try doing a few test renders with and without the CPU contributing, see how the times compare.

Matt_Brown

I found that GPU only works best on my rig. However, I do have CPU fallback enabled for when I max out the vRAM.

benniewoodell

I always have CPU turned off. When I leave it on, it seems like my renders are slower, and sometimes it falls to CPU from my GPU even though it shouldn't be doing that. When I click CPU off, those files render fully on the GPU. Not sure why that is, but that's been my experience so I never have it checked. 

nikijunpei81

Thank you for your response. I have a nvidia 3050. I tried with both, but it seems slower than the render i did with GPU only.

nonesuch00

nikijunpei81 said:

Thank you for your response. I have a nvidia 3050. I tried with both, but it seems slower than the render i did with GPU only.

I read about that situation about 6 months ago & your outcome is correct. The CPU is so slow that the GPU will finish before the CPU and your renders will take longer than GPU only.

rrward

I just put a 16-Core Skylake monster in my render rig (for non-DS reasons) and did some testing. Even that monster slows down GPU/CPU mixed renders. 

nakamuram002

Richard Haseltine said:

Try doing a few test renders with and without the CPU contributing, see how the times compare.

It doesn't seem to make much difference on my system - RTX 3070ti / Ryzen 5800x.  Maybe it is the complexity of the scenes that I render,  Mine are fairly simple, but I do use dForce Hair, both strand-based and "cloth".