<div dir="ltr"><div dir="ltr"><br></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Sun, Apr 4, 2021 at 10:26 AM D. Hugh Redelmeier via talk <<a href="mailto:talk@gtalug.org">talk@gtalug.org</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">| From: Evan Leibovitch via talk <<a href="mailto:talk@gtalug.org" target="_blank">talk@gtalug.org</a>><br>
<br>
Thanks for the more complete information.<br>
<br>
What the exact brand and model of your Radeon RX 550? Are you sure<br>
that the HDMI port conforms to HDMI 2.x?<br>
<br>
Remember that I'm not an expert.<br>
<br>
Jose Dias' experiment seems worthwhile.<br>
<br>
| The left (HDMI) screen will (randomly to me) do one of a few things:<br>
| <br>
| 1. Go off (the monitor reports lost signal) and back on after about 1-2<br>
| seconds.<br>
| <br>
| 2. Go off (no signal) for 3-4 seconds and then back on, briefly to flat<br>
| green or static and then normal.<br>
<br>
I would perhaps call that briefly blanking out. There is probably an<br>
accepted term for this but I don't of know one.<br></blockquote><div><br></div><div>Screen blanking is a feature of dpms, could try turning it off for the monitor.</div><div> <br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<br>
I doubt that that symptom has anything to do with the compute power of<br>
the GPU. It "feels" more like the monitor has been unhappy with<br>
something about the signal itself.<br></blockquote><div><br></div><div>I ran into similar problems with a dual monitor setting up IOMMU / Vt-d on intel. Blanking</div><div>the primary boot screen and no display on the other on boot up.</div><div><br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<br>
Some video cards have fewer clocks than outputs. Some outputs were<br>
required to share clocks. This could cause mysterious problems. I<br>
have no idea if that is the case here.<br>
<br>
Are you sure that HDMI is driving your left monitor at UltraHD<br>
resolution at 60Hz?<br>
<br>
| I've tried different cables, no difference.<br>
<br>
That would have been my first suggestion. I once had a mysterious<br>
problem fixed by a new HDMI cable. HDMI is complicated and made more<br>
so by papering over the complexity. As HDMI bandwiths increase, more<br>
marginal cables fail.<br>
<br>
Are any problems logged by the system about the time of these events?<br>
(The few times that I've tried to understand a Windows log have been<br>
very unpleasant and not at all useful.)<br>
<br>
Experiment: shut down the system, disconnect the right screen, and<br>
reboot. Does it flicker?<br>
<br>
Experiment: switch to mirroring (where each display shows the same<br>
thing). Does it flicker?<br>
<br>
Experiment: try running both monitors at a slower refresh rate.<br>
Does it flicker?<br>
<br>
Experiments: try running the monitors at a different refresh rates (if<br>
that's possible). Left slower than right. Also left faster than<br>
right.<br>
<br>
Experiments: try the same set of experiments, this time varying the<br>
resolution rather than the refresh rate.<br>
---<br>
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</blockquote></div><br clear="all"><br>-- <br><div dir="ltr" class="gmail_signature"><div dir="ltr"><div><div dir="ltr"><div>Russell<br></div></div></div></div></div></div>