http://amfeltec.com/products/gpu-oriented-cluster/
I'm looking at ways to expand my number of GPUs, for GPU rendering (Octane and RT).
I have run out of space in my WS case but don't want to re-build from scratch, hence this approach to extending the hardware seems logical. Another positive, is that no extra software licenses are needed.
It appears that in theory you can run four clusters (each with four GPUs) and have sixteen GPUs on one system! I'd probably just go for one cluster of four GPUs, in addition the existing GPU (running monitors) that is plugged directly into the WS mobo.
What do you think?