Using two GPU video cards Does anyone know, how can I check if I am using my two video cards?

It seem Blender is using only one of them. I have checked both on the user preferences settings. But reading temperatures in GPU-Z it seems Blender is using only one of them.

The first card card is Titan X maxwel and the other is GtX1080 TI pascal.

Please give guidance, I bought this new 1080Ti to speed up the render but is not helping much.
The easiest way to tell if it's using both cards is if you see two tiles being processed simultaneously when rendering.  I have three cards processing this scene and you can clearly see the little orange corners on each of the tiles:



Also, I'm sure you already know this, but in addition to checking the User Preferences, make sure you have GPU rendering enabled in the Properties Pane: