| From: Evan Leibovitch via talk <talk@gtalug.org> Thanks for the more complete information. What the exact brand and model of your Radeon RX 550? Are you sure that the HDMI port conforms to HDMI 2.x? Remember that I'm not an expert. Jose Dias' experiment seems worthwhile. | The left (HDMI) screen will (randomly to me) do one of a few things: | | 1. Go off (the monitor reports lost signal) and back on after about 1-2 | seconds. | | 2. Go off (no signal) for 3-4 seconds and then back on, briefly to flat | green or static and then normal. I would perhaps call that briefly blanking out. There is probably an accepted term for this but I don't of know one. I doubt that that symptom has anything to do with the compute power of the GPU. It "feels" more like the monitor has been unhappy with something about the signal itself. Some video cards have fewer clocks than outputs. Some outputs were required to share clocks. This could cause mysterious problems. I have no idea if that is the case here. Are you sure that HDMI is driving your left monitor at UltraHD resolution at 60Hz? | I've tried different cables, no difference. That would have been my first suggestion. I once had a mysterious problem fixed by a new HDMI cable. HDMI is complicated and made more so by papering over the complexity. As HDMI bandwiths increase, more marginal cables fail. Are any problems logged by the system about the time of these events? (The few times that I've tried to understand a Windows log have been very unpleasant and not at all useful.) Experiment: shut down the system, disconnect the right screen, and reboot. Does it flicker? Experiment: switch to mirroring (where each display shows the same thing). Does it flicker? Experiment: try running both monitors at a slower refresh rate. Does it flicker? Experiments: try running the monitors at a different refresh rates (if that's possible). Left slower than right. Also left faster than right. Experiments: try the same set of experiments, this time varying the resolution rather than the refresh rate.