I've got a Sapphire Pulse Radeon RX 590. I try to connect it via DisplayPort with my DELL monitor. But every 5 to 60 seconds I have got a blackout on the display. It's really only the display, as the content in a game or just desktop activities is going on. Also the menu of the display disappears, so it is like resyncing. Same for both DP outputs. With HDMI no trouble, but less accurate pictures (e.g. only 8 bit color depth).
Newest drivers installed, factory settings restored and played with the output parameters, without success.
Some further tests:
=> Dell P2415Qb with two different cable @ RX 590 DP => blackouts
=> Dell P2415Qb with two different cable @ RX 590 HDMI (only 30 Hz) => no blackouts
=> Dell P2415Qb @ R7 250 PD => no blackouts
=> Dell U2515b with two different cable PD@ RX 590 => no blackouts
Could it be, that the RX 590 with DisplayPort 1.4 causes trouble and the R7 250 with DP 1.2 doesn't? Any way to set the RX 590 to DP 1.2?