On Wed, 2024-05-08 at 11:08 +0100, John Pilkington wrote:
> It occurs to me that my new 'dual-boot' problems with F40 KDE might be 
> related to this, but I'm not clear how I could test it.  I've posted 
> both here and on the kde list.
> 
> I have two screen-devices, HDMI tv and vga monitor.  By default booting 
> is to Windows, but 'escape' early on goes to an HP-provided 
> boot-selection sequence and grub.
> 
> Choosing "modesetting" starts booting with both screens active, but 
> freezes shortly after a cursor appears.
> 
> "nomodeset" gives a usable system, but with the vga screen never active 
> and final HDMI resolution fixed at 800x600.
> 
> Could this perhaps be a conflict of hostnames set at power-on and by Fedora?

I wouldn't have thought so (re DNS, IPs, & DHCP).  Video output (other
than networked KVM kind of things) is direct hardware to monitor, no
network should be involved.  I don't recall you mentioning KVM, though
could have forgotten.  Normally, screen set up is long before
networking starts.

Manual modesetting overrides the OS automatically picking a graphics
mode, to some degree.  Normally a monitor identifies itself, and the
graphics system works out a list of compatible modes that the monitor
and the graphics card can both use, and picks the highest resolution
possible with the fastest refresh rate.

If you have a monitor that doesn't identify itself, or doesn't do it
properly (and some don't), or your graphic card is just as bad at it,
than manual overrides is the way to go.  I seem to remember it was Tom
Horsley who had a website page detailing his battles with such things.

Hardware KVMs can have the same problems with display ID data, they may
have a broken implementation of it.  Or only support one mode.  Or,
alternatively, they could be a solution, forcing a mode that works for
you.

If you simply prefer a different graphics mode (different scan/refresh
rates, different resolutions), then that should be possible to select
after you've booted up with the display settings.  800 by 600 is a bit
nasty.  While it may produce a screen size that some people want, many
GUIs expect bigger screen dimensions and don't fit, or you're left with
a looking-through-a-keyhole view of them.

This EDID info is sent over different wires (DDC) in the video
connector than the picture signal.  It is possible to have broken pins
in the plugs or sockets, or wiring in the cable, that stops this info.
If the cable can be completely unplugged from monitor *and* PC, it may
be worth trying another.  And sometimes a clean toothbrush scrub of the
connector contacts fixes problems up.
 
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