[Arm-dev] CentOS 7 KDE on Pi 3B+ video issue - strange

[Gordan Bobic]

Most of these adapters have various compatibility issues. I went through
about 4 before I found one that allowed my laptop to talk to the monitor I
wanted to attach to it. Some of the adapters worked on one machine, but not
on others, going to the same monitor. I don't know what causes these sorts
of compatibility issues but it's not specific to the Pi, it happens all
over the place on all sorts of devices, both high end and low end.


On Fri, Mar 15, 2019 at 11:10 PM kht-lists <kht-lists at protonmail.ch> wrote:

> I downloaded the referenced image a couple of days ago, burned it to a 16
> GB SD card and booted my Pi 3B+.  Fantastic! The Pi was connected with a
> HDMI to DVI cable to a Dell 19" monitor.
>
> I received in the mail a couple of HDMI to VGA adapters. The $4 generic
> ones which are all over ebay.  I have several which I have purchased over
> the years and the generally work fine.
> [image: adapter.png]
>
> I decided to test the new adapters with the Pi.  I connected one to the Pi
> and to a VGA cable to the same monitor (which has two inputs). I had NO
> video. No rainbow screen, no 4 raspberries screen, not test.  Same for the
> second adapter.  I tested the adapters on an Intel based PC. They worked
> fine.  But it gets stranger... I booted the same Pi, same new adapter,
> connected to the same monitor from an Ubuntu SD card. The video was fine!
> And stranger still... I tried 3 older adapters with the Pi, CentOS and the
> same cable and monitor. The video was again fine!
>
> These adapters have no manufacturer markings. They probably all came from
> the same factory in China. Obviously something changed in the devices and I
> do not expect to ever be able to figure that out. However, something is
> also different in the video (driver I guess?) signal from the Pi with
> CentOS vs. Ubuntu.  Can someone shed any light on this mystery?
>
> TIA,
>
> Ken
>
>
>
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>
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