GPU question - prolly a schoolboy howler...

[Burgess AK]

When in render settings I tick the box that says 'use all GPUs' and it doesn't seem to affect render times... sigh
Should this affect render times?

apologies if this is 'carbon' error

[bepeg4d]

Hi Burgess AK,
from your signature, it seems that you are working with 2x GTX 1080.
What are your settings in Devices panel?
Do you mind to share some screenshots?
ciao beppe

[Burgess AK]

Thanks Beppe, don't ask why I can't take an actual screenshot

[bepeg4d]

Hi Burgess AK,
the photo is more than enough, thanks
It seems that you are already working with all your GPUs active.
If you disable one of them, maybe the one connected to the monitor, then you can use the "Use all GPUs" option in Render Settings to have both GPUs rendering while in Picture Viewer/Render Queue, and you use only one GPU in Live View.
Note that you should leave enabled the “Use for tonemap" option, unless the PCI bus works at 1x, and activate the Priority for the GPU connected to the monitor.
ciao beppe

[Burgess AK]

Thanks for the reply Beppe

I apologise in advance for being a bit slow with this stuff.

My background is that I come from 25 years of Mac, I just recently got a PC because I wanted Octane and Mac were dragging their heels with GPU so I have a Mac set up for physical render and a PC for Octane.
Honestly, just the adaptation to PC has been a pretty big learning curve so please excuse my stupidity.


If you disable one of them, maybe the one connected to the monitor, then you can use the "Use all GPUs" option in Render Settings to have both GPUs rendering while in Picture Viewer/Render Queue, and you use only one GPU in Live View.
How do I go about doing this, a step by step would be a great help


Note that you should leave enabled the “Use for tonemap" option, unless the PCI bus works at 1x, and activate the Priority for the GPU connected to the monitor.
Ok I get the 'tonemap' thing, but I don't know what the PCI bus stuff or how to do this either. Again, a step by step would be a great help

apologies again...

[bepeg4d]

Hi Burgess AK,
I have made almost the same steps some years ago, with the exception that I still render also with my Mac, so I can understand your sense of confusion
If you want to temporarily disable one GPU, simply untick the first checkbox just before the name.
About PCI bus speed, if your GTX is connected directly, enable the Use for tonemap, if it is connected with special cable/riser, probably you have to untick this option, but I’m quite sure that you need to leave the option active with your setup.
ciao beppe

[Burgess AK]

Hi Beppe,

I ran this by the guys that did my PC build and waiting to hear from them how they rigged up the GPU cards, please hold

[Burgess AK]

did a bit of reading too, looks like my GPU's are "tethered" together, a gaming sort of set up.
I believe this is incorrect for optimum Octane perf?

Thanks again

[FrankPooleFloating]

Just disable SLI in NVidia Control Panel.

[Burgess AK]

Hit it, thanks Beppe