Help me when i load up games, it only uses my APU's Vega Mobile GFX, but its not using my Vega 6 iGPU how do i fix it?
The GPU in the APU is the iGPU. The "i" means "integrated". You can post your full system specs to be sure, but I'm going to guess you do not have a discrete (i.e. not part of the CPU) GPU at all.
