I recently picked up an RX 580, and after a completely fresh system and driver install I continuously get 3-4 blackscreen/loss of signal problems after booting my pc. Ill boot my pc, the signal will cut in an out 3-4 times every time I start, and then after about two minutes it will properly recognize my monitor and I do not have further blackscreens/loss of signal (so far).
This also happens in a similar fashion while using my RX Vega 64, but it will only blackscreen once at startup, and then it may randomly occur while idling at desktop.
This has been an issue over multiple driver versions as far back as I can remember (version 17.xx). The combination of this RX 580 and 18.3.3 have been the worst offender and or best means of duplicating results.
I'm currently using an Acer xr342ck monitor over DP via a certified Amphenol DP cable. The problem happens whether or not I set the monitors DP version to 1.1 or 1.2. This has also been tested on other DP cables and the problem is no different. I have also tested over HDMI in the past and the issue was still there.
FOR CLARIFICATION: Only one card is being/was used at a time, and only a single card was physically inside the pc at any one time.
Constantly bumping into issues like this leaves a very sour taste in my mouth, especially when purchasing so much AMD equipment that at the same time is incredibly expensive. This issue has been around for a long time, and from personal testing, results, and just the general nature of the issue it seems to be directly related to software problems. Would be lovely to see this fixed and be able to use all of my hardware properly...
ASRock x299 OC Formula
Sapphire RX 580 8GB nitro+ / XFX RX Vega 64
Acer xr342ck (over DP)
EVGA 750w G2 PSU
W10 Home 64-bit
If you are running both the Vega64 and the RX580 at the same time, your PSU is probably way underpowered which could be causing the blackouts since the GPU card aren't getting proper power to them. You have a 750 watt PSU which is barely above minimum to run a RX Vega64 GPU card.
Here is the minimum PSU total system wattage you need for just one GPU card:
RX Vega 64 - 700 watt PSU
RX580 - 550 Watt PSU
To see if it is a PSU problem, Remove your RX Vega64 card from your computer and just use the RX580 and see if the blackouts continue or get better or worse or stays the same. Since the RX580 uses the least amount of power is why I suggested using that card first.