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To make an old Samsung monitor work with my Raspberry Pi (Pi 3 Model B+) I had to set the hdmi_boost option in the /boot/config.txt to 7 (without that it shows green vertical lines, or green snow, depending on the HDMI-cable I use)

After a while I connected my Pi to my other monitor (Eizo) (with a HDMI to DVI connector) - which worked fine for the Pi before. I forgot to remove the hdmi_boost=7 settings. This lead to the following situation: The monitor remained black and only showed an Error Message: "dotClock: 0 out of range" . Ever since my Pi can only use the lowest resolution with my Eizo monitor (works well with the Samsung), to achive this I set the hdmi_safe option to 1 in the /boot/config.txt file. When I connect the Eizo monitor to an old computer graphics card via the VGA connector it works perfectly well.

Thus I wonder: Is it possible to damage the DVI electronics by setting the hdmi_boost option to a high value such as 7.

Kind regards Stefan

Stefan
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It's a little unclear exactly what CONFIG_HDMI_BOOST does. The documentation says it "Configures the signal strength of the HDMI", and then gives an example of increasing the value to compensate for longer cables. Longer cables increase resistance, so this suggests that it's compensating by increasing voltage slightly. These articles on HDMI signal boosters suggest that boosters work by increasing voltage, which agrees.

So is an increase in signal voltage a risk? It depends on how much the Pi boosts voltage by, and I haven't been able to find any information on this. The DVI specification gives the signalling voltage as a fairly large range of 150 to 1200 mV with a maximum of 1560 mV, which suggests it should be fairly tolerant to voltage boosts. Based on this I think its unlikely that the Pi is increasing voltage high enough to cause damage. Of course, this depends also on how well both the Pi and Monitor implement their specifications.

In a similar situation, this post suggests that the cable could be the culprit. Personal experience on my part has shown that some monitors don't correctly communicate EDID monitor display information to Linux devices, and so native display resolutions don't work. In that case the easiest solution is to switch monitors.

Fred
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