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

kht-lists

kht-lists at protonmail.ch
Fri Mar 15 23:10:25 UTC 2019


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.
[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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