TLDR: Two of my three 4k60 monitors are experiencing occasional flickering, but only in Windows
I have a lot of screen real estate, 3 monoprice 4k60 monitors and one monoprice 1080p pen tablet. All of these are hooked up through a Vega56, with the three 4k60 monitors being hooked up through display port and the 1080 pen tablet actually going to a passive selection box so I can switch to my OSVR when I’m down for some VR gaming. All of it works fine in Linux, but in Windows 10 (1803, 1809, or 1909), with many versions of the AMD driver for the Vega56 tested, two of the 4k screens will flicker off briefly before coming back on about once every half hour. They do not flicker off at the same time, only one or the the other, though I have no reason to think there’s any reason it couldn’t happen to both at the same time. The two that experience the flicker are a different model from the 3rd. Unfortunately I can’t easily get to the product pages of either to provide more information, but the most obvious relevant differences would be that the two that are experiencing the problem both support FreeSync and HDR (albeit the HDR support is trash, and I’ve never bothered to get FreeSync Running) it doesn’t appear that FreeSync being enabled/disabled has any effect on the issue. Changing what port things are connected to or what cable each is using also doesn’t appear to help matters. My current guess is that getting some very shielded cables might help, but I’ve also already gone down that rabbit hole once, and given it works fine in Linux that doesn’t make tons of sense.
Coppied from the Radeon Settings window
4K monitors with issuses:
Horizontal Timing Total - 4400
Horizontal Timing Display - 3840
Horizontal Timing Front Porch - 176
Horizontal Timing Sync Width - 88
Vertical Timing Total - 2250
Vertical Timing Display - 2160
Vertical Timing Front Porch - 8
Vertical Timing Sync Width - 10
Horizontal Timing Polarity - Positive
Vertical Timing Polarity - Positive
Interlaced/Progressive - Progressive
G.Pixel Clock (KHz) - 593400
G.Refresh Rate (Hz) - 59.9394
HDMI Link Status Monitoring - Disabled
Current Link Settings - 5.4 Gbps x 4
RGB 4:4:4 8bpc
4k monitor that works fine
Horizontal Timing Total - 4000
Horizontal Timing Display - 3840
Horizontal Timing Front Porch - 48
Horizontal Timing Sync Width - 32
Vertical Timing Total - 2222
Vertical Timing Display - 2160
Vertical Timing Front Porch - 3
Vertical Timing Sync Width - 5
Horizontal Timing Polarity - Positive
Vertical Timing Polarity - Positive
Interlaced/Progressive - Progressive
G.Pixel Clock (KHz) - 533280
G.Refresh Rate (Hz) - 60
HDMI Link Status Monitoring - Disabled
Current Link Settings - 5.4 Gbps x 4
RGB 4:4:4 8bpc
I can provide any additional info requested using Linux (Arch) or Windows.