High CPU usage on 390.25 ubuntu 16.04 kernel 4.13 Openbox GTX 970 with Displayport only connection

Good day!
Come across to the following situation. I have Gigabyte GTX 970 with 2 DVI, 1 HDMI and 3 DP connectors
When I connect my monitor with HDMI or DVI-HDMI connector works fine, but when I connect my HDMI monitor with DP-HDMI have 60-70% CPU load on Xorg. Only DP. Also I found when I connect DVI-HDMI I don’t have audio in my monitor. Maybe is there some way to enable audio on DVI connectors?
This situation happens even without any application loaded.
Thanx in advance