Hi,
I have seen the strange effect a few times here during my tests - if I use 2x2080ti/1080ti/2950x than the render time (45min) is slower than if I use the three GPU only (41min) (V-Ray for Rhino). I suppose so the full used CPU cause that the GPU get less data and are slower. Is this a known issue?
Best-
Micha
Maybe one reason for the slower hybrid mode was that my CPU got to much heat by the GPUs and CPU speed was throttled. I applied new thermal paste and the temps are better now. I short test shows me 8min:18s vs. 7min:27s (GPU vs. Hybrid). So, the hybrid mode is a little bit faster now.
New interior test
CPU 2950x 10min
3xGPU 3min
Hybrid 3:40min
CPU temperature below 80°C
Any ideas why the Hybrid mode cause a slow down?
interesting about this issue, do you finally know what happened?
which are the 3 cards you use?
2x2080ti + 1x1080ti
Here you find some more tests and latest conclusions. This topic is accidentally moved to the gallery section.
So far I understand if the CPU is working in GPU mode emulation than it is not very effective and much slower than a good high end card. Also the power of the CPU is wasted for rendering, instead to use for feeding the three much more powerful GPU. But if you own weak GPU power and a good CPU than the hybrid mode could be useful to get GPU rendering running faster.
Maybe get dual CPU setup then? 
what a dream…
I suppose to use a CPU in GPU mode is wasting power and it’s better to use high end CPUs in CPU mode. 
its a pity, hybrid could be the definnitive way if uses cpu power, with a 2950x and 2080ti toghether…
Micha, do you have a special configuration using different cards in the same machine (2080 ti + gtx 1080 ti and 1050)?, any problem mixing different architectures? any driver recommended for that?
can you explain me how you have installed this differents cards
(i have a 2950x too + titan x pascal thinikng about put 2x2080ti + my titan )
I didn’t any special. Only downloaded the recommended driver and installed. No problems, anything works very good together.
Does Chaos group list recommended drivers and keep it updated? I’ve been having issues and this might be part of the fix.
You can look for the driver version here on the top of this side: