Vega 56 on Mojave Installation

Hey guys, just a quick doubt... i've got a very small and partial area on installer's display. Is this related to my Vega 56 somehow? My mobo (DX79SI) and my cpu (I7-3960X) don't have internal graphics, so i can't get video without my gpu. I've also tried to change Clover resolution (1360x768) using config.plist. But without success. Is this issue usual?
1.jpeg

Author: Fuhrer