http://www.pcgamer.com/amds-new-vega-drivers-give-multi-gpu-support/

Good luck finding a single Radeon RX Vega graphics card in stock at a fair price, let alone two. But if you do happen to snag a couple of Vega cards, you now can configured them in Crossfire with AMD's latest Crimson ReLive driver release.

AMD's Radeon Software Crimson ReLive Edition 17.9.2 release introduces 2-way multi-GPU support for Radeon RX Vega cards, along with a multi-GPU profile for Project Cars 2, which released today.