A promotional video from RenderStream, providers of multi-GPU systems for rendering and science, does a great job of also promoting OctaneRender on multiple GPU’s.

octanerender demonstration running on a RenderStream VDACTr8 with 8 GTX 580 GPUs. In this video we demonstrate the rapid visual feedback one can expect when using an 8 GPU system in a detailed interior scene. We also show how well octanerender perfroms when scaling from 1-8 GPUs.

via octanerender running on a RenderStream VDACTr8 with 8 GTX 580 GPUs – YouTube.