Intermittent Monitor Blanking

tl;dr: Using a better-rated HDMI switcher improved the situation

For the past… maybe six months to a year one of the monitors I have has been ‘blanking’. That is, it will display properly most of the time, but intermittently go blank for around three seconds before the display reappearing. Strangely, the behaviour only occurred:

  • under Windows, not Linux
  • when using an HDMI switcher

For whatever reason, the issue got much worse in the last couple of weeks, where instead of happening once every five to sixty minutes (or sometimes not at all), it was happening back-to-back, several times per minute with an intolerable frequency. The situation was untenable.

I wondered about interference from other nearby cables, but adjusting them didn’t make any discernable difference. The monitor was running at 59Hz, but stepping it up to 60Hz made no difference either (and Windows 10 set it back to 59Hz). If anything, increasing the frequency may have made the problem worse.

So I figured the issue was the cheap HDMI switcher that I have. I don’t quite recall the circumstances of buying it (never a good sign), but it would have been cheap and therefore unlikely to be rated for 2560x1440x60Hz. After replacing the switcher with one with was rated for ? 2560x1440x60Hz, the issue seems to have mostly resolved- there was *one blank, but I think I can tolerate that.

For anyone else having a similar problem, allquixotic had the following to suggest for potential causes:

Periodic blanking could be: loose cable/connector; bad HDMI port; bad HDMI codec on the GPU/mobo; EMI interference on the cable (e.g., crosstalk by contact with another cable); or, yeah, insufficient cable quality for the data quantity being pushed… also could be pure software

you know, it could simply be Windows driving more data to the monitor; have you verified Windows isn’t overclocking the monitor beyond 60 Hz?

or it might be a GPU issue — Linux tends not to even use the GPU very often unless you’re decoding video, using the animation “whizzy” effects of a compositing window manager, or explicitly an OpenGL application (which in modern times could actually be a typical web browser, but not for everything)

*: I can’t quite explain why the problem only occurred under Windows, but I’ll wave my hands and say “driver differences” while nodding sagely.

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