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I'm trying to hook up an old PC to my TV. It has an NVIDIA GT128 graphics card. I currently have both VGA and HDMI connections from the PC going to the TV.

When I power up I can see the BIOS messages then the grub loader menu (I'm using Debian 8) on both the VGA and HDMI outputs, but during boot the HDMI output suddenly stops. It's at the same time during the boot process that the screen resolution changes (framebuffer?).

If I start up Xorg, the problem is the same.

xrandr says:

HDMI-1 connected 1920x1080
VGA-1 connected 1920x1080

Which I believe would imply that HDMI-1 hasn't been disabled. I've tried disper to switch to the HDMI output, but I simply end up with no display at all (as it turns off the VGA output).

2

Just use xrandr

xradnr --output HDMI-1 --auto

Don't forger! man xrandr

You will probably need to fix pulse audio output from there.

In case you are using Xorg with a Desktop Enviroment, there will probably be some application that configures the display resolution.

There may also be some Login Manager script that sets the display.

0

xrandr is good for Xorg, but if you want ttys to output to HDMI too, you can try appending video=HDMI-A-1:D to your bootline. This will force the HDMI output to be enabled (D) and to be used for video output.

See details about the video= parameter to better understand what it does. As this parameter could have side effects (if it doesn't work, you would end up with no video output), you should first try it temporarily, and only if it works set it permanently. See how to add temporary or permanent kernel boot parameters in grub for an explanation on how to do that.

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