Any reliable and comprehensive GPU/CPU cycles rendering study OK, I'm a 10 year+ user and about to upgrade GPU. Having tested my previous builds I know the following:


the CPU can bottleneck the GPU rendering at some point If I Overclock my CPU my gtx970s gets a slight boost and if I underclock it the GPUs dont even throttle to maximum frequency.
I know each gpu needs a single thread while rendering, at least that process is single threaded.


However I have no idea what the CPU does exactly and how much a certain GPU power is bottlenecked by a certain CPU power. It would be nice to have a study that relates CPUs to GPU power, at least in terms of modern CPU frequency and teraflops.

Anyone done something similar or thinking about it?

Thanks
I don't think the GPU power is bottlenecked by CPU in any way. You either render using CPU or GPU. If you're using a CPU you need to set the tile size to some small number like 16 x 16 or 20 x 20 so that each CPU thread will be responsible for one of these tiles and the process becomes more efficient this way. When using a GPU for rendering you need to set the tile size to a higher number such as 224 x 224 and so on so that you can benefit from using a GPU.

Blender OpenData might give you some ideas on what GPUs/CPUs are better for rendering.